209 eee labmanual_28 april2012

8/12/2019 209 Eee Labmanual_28 April2012

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AIET/Department of Electrical Engineering/209 EEE LAB Page 1

DEPARTMENT OF ELECTRICAL ENGINEERING

LAB-MANUAL

II SEM ALL BRANCHES

209 ELECTRICAL & ELECTRONICS

LAB


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INDEX

Sr. No. Content Page No.

1 RTU Syllabus

2 Experiment List

3 Lab PEO

4 Lab Plan

5 Lab Ethics

6 Instructions

7 Experiment-1 To study of various graphical symbols used in electrical &

electronics systems. (Beyond Syllabus)

8 Experiment-2To study of single line diagram of a power system and a

distribution sub-station and basic functional study of main components usedin power systems.

9 Experiment-3a) To basic functional study of components used in

house wiring and to make house wiring connections which includes 1-phase

energy meter, MCB, ceiling fan, tube light, three pin socket etc.

b) To make a connection for stair case wiring which can operate a lamp

from two different positions?

10 Experiment-4 a) To study the construction and basic working of ceiling fan

and connections of ceiling fan with regulator.

b) To study the construction and basic working of single phase induction

motor and connect it through auto-transformer to run and vary its speed.

11 Experiment-5a) To study the construction and connection of single phase

transformer and auto-transformer. Measure input and output voltage and find

turn ratio.

b) To study the construction of a core type three phase transformer. Perform

star and delta connection on it and find relation between line and phase

voltages.

12 Experiment-6a) Identification, testing and applications of various resistors,

inductors, capacitors, PN-diode, Zener diode, Photo diode.

b) Identification, testing and applications of BJT, photo transistor, LED,

LCD, FET, UJT, SCR

13 Experiment-7a) To functional study of CRO, function generator and analog

& digital multi-meters.

b) To study of single phase half wave and bridge rectifier, obtain output

voltage and current waveforms. Also find the effects of filters on these

waveforms.

14 Experiment-8a) To basic functional study and connection of moving coil &

moving iron ammeters & voltmeters, dynamometer type wattmeter and

analog & digital energy meter.

b) To study three phase squirrel cage induction motor and run it at no load

and measure its voltage, current, power and power factor. Reverse the

direction of rotation also.


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Sr. No. Content Page No.

15 Experiment-9a) To study the construction, circuit, working and application

of the Fluorescent lamp and Sodium vapour lamp.

b) To study the construction, circuit, working and application of the Mercuryvapour lamp, Halogen lamp and Neon lamp.

16 Experiment-10 a) To study the BJT amplifier in common emitter

configuration. Measure its voltage gain. Plot Gain v/s Frequency response

and calculate its bandwidth.

b) To study different types of wires and cables used in electrical/electronic

systems. (Beyond Syllabus)

17 Experiment-11a) To study the construction and basic working of SCR.

b) To study the single phase half wave and full wave (bridge) converter

(controlled rectifier) and observe the effect of firing angle on voltagewaveform.

18 Experiment-12 a) To study the different types of transformer used in

electrical/electronic systems. (Beyond Syllabus)

b) To study connections and testing of electric iron.(Beyond Syllabus)

19 Lab Evaluation Format


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RTU SYLLABUS

CLASS:I Yr. II Sem. Evaluation

Branches :CS/ECE/EE/ME/IT

Practical Hrs: 2 Hr/week

Examination Time: 2 Hrs

Maximum Marks: 75 Sessional (45) & Practical(30)

A. ELECTRICAL LAB

1. Single line diagram of a power system a distribution sub-station and basic functional study of main

components used in power systems.

2. Make house wiring including earthing for 1-phase energy meter, MCB, ceiling fan, tube light, three

pin socket and a lamp operated from two different positions. Basic functional study of components used

in house wiring.

3.Study the construction and basic working of ceiling fan, single phase induction motor and three phasesquirrel cage induction motor. Connect ceiling fan along with regulator and single phase induction motor

through auto-transformer to run and vary speed.

4. (a) Basic functional study and connection of moving coil & moving iron ammeters and voltmeters,

dynamometer, wattmeter and energy meter. (b) Run a 3-phase squirrel cage induction motor at no load

and measure its voltage, current, power and power factor. Reverse the direction of rotation.

5. Study the construction, circuit, working and application of the following lamps: (i) Fluorescent lamp,

(ii) Sodium vapour lamp, (iii) Mercury vapour lamp, (iv)Halogen lamp and (v) Neon lamp

6. (a) Study the construction and connection of single phase transformer and auto-transformer. Measure

input and output voltage and fin turn ratio. (b) Study the construction of a core type three phase

transformer. Perform star and delta connection on a 3-phase transformer and find relation between line

and phase voltage.

B. ELECTRONICS LAB

7.Identification, testing and applications of resistors, inductors, capacitors, PN-diode, Zener diode, LED,

LCD, BJT, FET, UJT, SCR, Photo diode and Photo transistor.

8(a) Functional study of CRO, analog & digital multi-meters and function / signal generator. (b) Study

the single phase half wave and bridge rectifier and effects of filters on waveform.

9.Study the BJT amplifier in common emitter configuration. Measure voltage gain, plot gain frequency

response and calculate its bandwidth.

10.(a)Study the construction and basic working of SCR. (b) Study the single phase half wave and bridge

controlled rectifier and observe the effect of firing angle on waveform.


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LIST OF EXPERIMENT

1. To study of various graphical symbols used in electrical & electronics systems. (Beyond Syllabus)

2. To study of single line diagram of a power system and a distribution sub-station and basic functional

study of main components used in power systems.

Rotor# 1

3. a) To basic functional study of components used in house wiring and to make house wiring

connections which includes 1-phase energy meter, MCB, ceiling fan, tube light, three pin socket etc.

b) To make a connection for stair case wiring which can operate a lamp from two different

positions?

4. a) To study the construction and basic working of ceiling fan and connections of ceiling fan with

regulator.

b) To study the construction and basic working of single phase induction motor and connect it

through auto-transformer to run and vary its speed.

5. a) To study the construction and connection of single phase transformer and auto-transformer.

Measure input and output voltage and find turn ratio.

b) To study the construction of a core type three phase transformer. Perform star and delta

connection on it and find relation between line and phase voltages.

6. a) Identification, testing and applications of various resistors, inductors, capacitors, PN-diode, Zener

diode, Photo diode.

b) Identification, testing and applications of BJT, photo transistor, LED, LCD, FET, UJT, SCR

7. a) To functional study of CRO, function generator and analog & digital multi-meters.

b) To study of single phase half wave and bridge rectifier, obtain output voltage and currentwaveforms. Also find the effects of filters on these waveforms.

Rotor# 2

8. a) To basic functional study and connection of moving coil & moving iron ammeters & voltmeters,

dynamometer type wattmeter and analog & digital energy meter.

b) To study three phase squirrel cage induction motor and run it at no load and measure its voltage,

current, power and power factor. Reverse the direction of rotation also.

9. a) To study the construction, circuit, working and application of the Fluorescent lamp and Sodium

vapour lamp.

b) To study the construction, circuit, working and application of the Mercury vapour lamp, Halogenlamp and Neon lamp.

10. a) To study the BJT amplifier in common emitter configuration. Measure its voltage gain. Plot Gain

v/s Frequency response and calculate its bandwidth.

b) To study different types of wires and cables used in electrical/electronic systems.

(Beyond Syllabus)

11.a) To study the construction and basic working of SCR.

b) To study the single phase half wave and full wave (bridge) converter (controlled rectifier) and

observe the effect of firing angle on voltage waveform.

12.a) To study the different types of transformer used in electrical/electronic systems.

(Beyond Syllabus)

b) To study, connection and testing of electric iron.


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PROGRAM EDUCATION OBJECTIVES

BRANCH: 1ST

YEAR/SEMESTER: II

SUBJECT: - 209 ELECTRICAL & ELECTRONICS ENGG. LAB

Total Marks: 75 Practical: 2hrs/weekInternal Marks: 45

External Marks: 30

(1)Lab Objectives

I. To describe how Electrical Engineering has strong background in basic science and general day

to day life.

II. To understand the necessary techniques of circuits, hardware, and electrical tools for modern

engineering applications.

III. To comprehend, analyze design of circuits and create a novel products and solutions for the real

life problem.

IV. To describe the ability to design electrical circuits and its different parameters.

V. To implement professional and ethical attitude, effective Communication Skills, teamwork Skills

and an ability to relate electrical engineering issues to broader social context.

(2)Outcomes

a. Students can understand the knowledge of differential equations, nodal analysis, KCL, KVL,

methods of control of motors, types of wiring, types of lamps, etc.

b. Students can understand the ability to identify, formulate and solve electrical engineering

problems.

c. Students gain the ability to design electrical circuits and conduct experiments with different types

of circuits and load, analyze and interpret data.

d. Student can understand the design of electrical circuits and its different parameters.

e. Student gains the ability to visualize, work on laboratory with safety along with multidisciplinary

tasks.

f. Student can understands the modern engineering tools and software like PLC,MATLAB,My

Power, E-Tab, etc to analyze problems.

g. They gain the knowledge of professional degree holder and ethical responsibilities.

h. Students attains the sound knowledge of basics of electrical engineering.

i. Students understand the impact of electrical engineering and its solutions on daily lifes.

j. Students develop confidence for self education and ability for life-long learning.k. In depth knowledge of various electrical models and standard provide professional

compatibilities with Public Sector Undertaking like NTPC, BHEL, NPCIL,etc.


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(3)Mapping of lab objectives with outcome

(4)Important topics:

1. Testing of celling fan.

2. Single line diagram of power system.

3. Connection of transformer (1-phase and 3- phase).

4. Circuit connection of different types of lamps.

(5)Topic beyond the syllabus:

1. Study of various graphical symbols used in electrical & electronics systems

2. Study different types of wires and cables used in electrical/electronic systems.

(6)Text Book/Reference Books:

Sr. No Book Author Publication

1 A Text Book of Electrical

Technology

B.L.Theraja

A.K.Theraja

S.Chand

2 Basic Electrical Engineering Jimmie J Cathey

Syed S Nasar

Tata Mcgraw Hill

3 Basic Electrical Engineering V.K. Mehta S. Chand

(7)Instructional methods

1. Laboratory

2. Assignment

(8) Learning material consists of :

1. Text

2. Multimedia material (videos, text with animations)

3. Links to learning objects

4. Worked out projects

Outcomes

LabObjective

a b c d e f g h i j k

I X X X X X X

II X X X X

III X X X

IV X X

V X X X X X X X X


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(9) Relationship to course to program outcomes:

1. This course is required for all electrical and electronics engineering students and has significant

relationship with the program objective for electrical and electronics engineering.

2. To train students with good engineering breadth so as to comprehend, analyse, design and create

solution for real time problems.

(10)Additional seminar/workshops:

NA

(11) Assessment of Outcomes:

1. Internal practical exam (one in each semester)

2. End term practical exam (Conducted by RTU,KOTA)

3. Viva-voice

(12) Relation of course to program outcomes:

This course is required for all electrical and electronics engineering students and has significant

relationship with the program objective for electrical and electronics engineering.


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LAB PLAN

EXPERIMENT DITRIBUTIUON CHART

Exp No.

1 2 3 4 5 6 7 8 9 10 11 12Turn

No.

1All Groups

G1-G5

2

ROTOR-1

G1/G1'

G2/G2'

G3/G3'

G4/G4'

G5/G5'

3

G5/G5

'

G1/G1

'

G2/G2

'

G3/G3

'

G4/G4

'

4

G4/G4'

G5/G5'

G1/G1'

G2/G2'

G3/G3'

5

G3/G3'

G4/G4'

G5/G5'

G1/G1'

G2/G2'

6

G2

/G2'

G3

/G3'

G4

/G4'

G5

/G5'

G1

/G1'

7

ROTOR-2

G1/G1'

G2/G2'

G3/G3'

G4/G4'

G5/G5'

8G5/G5'

G1/G1'

G2/G2'

G3/G3'

G4/G4'

9

G4/G4'

G5/G5'

G1/G1'

G2/G2'

G3/G3'

10

G3/G3'

G4/G4'

G5/G5'

G1/G1'

G2/G2'

11

G2/G2'

G3/G3'

G4/G4'

G5/G5'

G1/G1'

12 INTERNAL PRACTICAL EXAMINATION


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LAB ETHICS

DOs

1. Enter the lab on time and leave at proper time.

2. Keep the bags outside in the racks.

3. Utilize lab hours in the corresponding experiment.

4. Make the Supply off the Kits/Equipments after completion of Experiments.

5. Maintain the decorum of the lab.

Donts

1. Dont bring any external material in the lab.

2. Dont make noise in the lab.

3. Dont bring the mobile in the lab.

4. Dont enter in Faculty room without permission.

5. Dont litter in the lab.

6. Dont carry any lab equipments outside the lab

We need your full support and cooperation for smooth functioning of the lab.


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INSTRUCTIONS

BEFORE ENTERING IN THE LAB

1. All the students are supposed to prepare the theory regarding the present Experiment.

2. Students are supposed to bring the practical file and the lab copy.

3. Previous experiment should be written in the practical file.

4. Object, Apparatus Table & Brief Theory of the current practical should be written in the

lab copy.

5.

Any student not following these instructions will be denied entry in the lab and Seasonal

Marks will be affected.

WHILE WORKING IN THE LAB

1. Adhere to experimental schedule as instructed by the faculty.

2.

Record the observations in lab copy & checked by the faculty

3. Each student should work on his assigned table of the lab.

4. Take responsibility of valuable accessories.

5. Concentrate on the assigned practical and be careful.

6. If anyone is caught red-handed carrying any equipment of the lab, then he will have to face

serious consequences.


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EXPERIMENT # 1

OBJECT: To study of various graphical symbols used in electrical & electronics systems.

THEORY: Some basic symbols are

Sr.

No.COMPONENTS SYMBOLS

DESCRIPTION

1. RESISTOR

A resistor is a two-terminal electrical or

electronic component that resists an electric

current by producing a voltage drop between

its terminals in R= V/I accordance with Ohm's

law: The electrical resistance is equal to the

voltage drop across the resistor divided by the

current through the resistor

2.VARIABLE

RESISTOR

Variable resistors consist of a resistance track

with connections at both ends and a wiper

which moves along the track as you turn the

spindle

3.CAPACITOR

A capacitor is an electrical device that can

store energy in the electric field between a pair

of closely spaced conductors (called 'plates').

When current is applied to the capacitor,

electric charges of equal magnitude, butopposite polarity, build up on each plate.

4

ELECTROLYTIC

CAPACITOR

An electrolytic capacitor is a type of

capacitor typically with a larger capacitance

per unit volume than other types, making them

valuable in relatively high-current and low-

frequency electrical circuits

5INDUCTOR

An inductor is a passive electronic component

that stores energy in the form of a magnetic

field. In its simplest form, an inductor consists

of a wire loop or coil

6 TRANSFORMERA transformer is a device that transferselectrical energy from one circuit to another

through a shared magnetic field.

7MOTOR

An electric motor converts electrical energy

into mechanical energy. The reverse process,

that of converting mechanical energy into

electrical energy, is accomplished by a

generator or dynamo.

8 VOLTMETER

A voltmeter is an instrument used for

measuring the electrical potential differencebetween two points in an electric circuit


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Sr.

No.COMPONENTS SYMBOLS

DESCRIPTION

9AMMETER

An ammeteris a measuring instrument used to

measure the flow of electric current in a

circuit. Electric currents are measured inamperes, hence the name.

10WATTMETER

The Wattmeteris an instrument for measuring

the electric power or the supply rate of

electrical energy (Watts) of any given circuit.

11BATTERY

A galvanic cell is an electrochemical cell that

stores chemical energy and makes it available

in an electrical form, and a battery is a string

of two or more cells in series. Other types of

electrochemical cell include electrolytic cells,

fuel cells, flow cells, or voltaic cells.

12 FUSE

In electronics and electrical engineering a fuse,

short for 'fusible link', is a type of over current

protection device. Itsessential component is a

metal wire or strip that melts when too much

current flows.

13 SWITCH

A switch is a device for changing the course

(or flow) of a circuit.

14EARTH To represent zero potential

15

WIRES (JOINED) Electric wiring (joined) connects one part of

the circuit to the other.

16WIRES (NOT

JOINED)

Electric wiring (not joined) isolates one part

of the circuit from the other.

17 D C SUPPLY

A D. C. supplyis a fixed supply voltage with

no ripples.

18

SINGLE PHASE

A C SUPPLY

2 wire supply system having 1 phase and one

neutral wire at a fixed frequency of supply

voltage

19 3 PHASE AC

SUPPLY

3 phases each having a 120 phase shift with

the other at a fixed frequency.


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EXPERIMENT # 2

OBJECT

Single line diagram of a power system and a distribution sub-station and basic functional study of

main components used in power system.

THEORY

An electrical power system may be divided into three main components mainly the generation system,

the transmission system and the distribution system.

Generation system

Generationis predominantly accomplished by thermal power plants equipped with steam turbines using

traditional fuel (coal, oil, gas, etc.) or nuclear fuel, and/or hydroelectric plants (with reservoir or basin,

or fluent-water type). Generation also can be accomplished by thermal plants with gas turbines or diesel

engines, geothermal power plants (equipped with steam turbines), and other sources (e.g., wind, solar,

tidal, chemical plants, etc.) whose actual capabilities are still under study or experimentation.

Transmission system

The transmissionsystem includes an extensive, relatively meshed network. A single generic line can, forexample, carry hundreds or even thousands of megawatts (possibly in both directions, according to its

operating conditions), covering a more or less great distance, e.g., from 10 km to 1500 km and over. The

long lines might present large values of shunt capacitance and series inductance, which can be, at least

partially, compensated by adding respectively shunt (inductive) reactors and series capacitors.

Distribution system

The task of each generic distributionnetwork at high voltage (HV), often called a sub-transmission

network, is to carry power toward a single load area, more or less geographically extended according to

its user density (e.g., a whole region or a large urban and/or industrial area). The power transmitted by

each line may range from a few megawatts to tens of megawatts. Electric power is then carried to each

user by means of medium voltage (MV) distribution networks, each line capable of carrying, for

example, about one megawatt of power, and by low voltage (LV) distribution networks. To reduce the

total amount of reactive power absorbed, the addition of shunt capacitors might be helpful (power

factor correction).


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F ig2.1 Layout of Power Supply Network

Substations

At many systems in the line of power system, it may be divided and necessary to change some

characteristics of electrical supply.

Classification of substation

The substations are mainly classified according to service requirement and construction features.

1.Transformer

2.Power factor

3. Frequency changer

4.Converter

5.Indoor

6.Outdoor

7.Underground

8.Pole mounted

EQUIPMENT USED IN POWER SYSTEM

1. BusBar It is a copper bar, operator at constant voltage. IT is terminated at both ends by using

insulator.


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2. Insulator These are usually made up of porcelain material. These support the conductor and

continue the current to the conductor.

3. Isolating switches An isolator is essentially a knife switch and is designed to open a circuit used

no load.

4. Circuit Breaker This can open or close circuit under normal as well as fault condition.

5. Power Transformer This is used in substations to step up or step down voltages.

(a) Instrument transformer The line is substations operate at high voltage and carry current

of thousand amperes. These are of two types: Current X-mer, Potential X-mer.

6. Relays This is used to detect the faults

7. Surge arrester or lightening arrester These are used for safety point of view.


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F ig.2.2 66kv Sub stations

RESULTSingle line diagram of a power system and a distribution sub-station and basic functional

study of main components used in power systems.


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VIVA QUESTIONS

1.What do you mean by single line diagram?

2.What do you mean of primary transmission?

3.What do you mean of primary distribution?

4.What is secondary transmission?

5.What do you mean of secondary distributing?

6.What is transmission line?

7.Why use of isolator in power system?

8.What is circuit breaker?

9.What is the use of circuit breaker?

10.What is the power source?

11.What is the service main?

12.What is the feeder?

13. What is the use of distribution transformer?

14. What is the use of transformer in transmission?

15. What is isolator?


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EXPERIMENT # 3(A)

OBJECT To make house wiring including Earthing for Single Phase Energy Meter, M.C.B, and

a Lamp operated from two different positions.

APPARATUS

S.NO. ITEMS RATING QUANTITY

1. Two way switch 6 ampere250 volt 2

2. Switch 6 ampere250 volt 4

3. Indicator ------------------------- 1

4. M.C.B. 6 ampere ,250 volt, DPST Type 1

5. Holder -------------------------- 26. Bulb 100 watt , 250 volt 2

7. Tester 100 watt , 250 volt 1

8. 3 Pin Socket 6 ampere , 250 volt 1

9. Tube light 40 watt , 250 volt 1

10. Fan with Reg. 12 Pole, Sweep 1200mm 220-230 volt 1

11. Energy Meter 1 Phase , 250 volt 1

12. Wire Stripper 100 mm 1

THEORY

A network of wires connecting various accessories for distribution of electrical energy from the

suppliers meter board to the numerous electrical energy consuming devices such as lamps, fans and

other domestic appliances through controlling and safety devices is known as wiring system. The

suppliers service cable feeding an installation terminates in what is usually called the service fuses. In

an ordinary house the service fuse is called as service cutout. Such cutouts including service meters

remain the property of the supplier and represent the furthest point of the supplier responsibility. The

point at which the consumer's wiring is connected into cutout is known as point of commencement of

supply or consumer's terminals. From consumer terminals onwards the supply cables are entirely underthe control of consumer's and so laid out as per his selection. A typical house wiring circuit is shown in

fig. 3.1


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F ig 3.1 Connection diagram of H ouse wir ing

F ig 3.2Distr ibution Board System

In distribution board system, which is most commonly adopted for distribution of electrical energy in a

building, the fuses of various circuits are grouped together on a distribution board, some times simply

known as fuse board. The two copper strips, known as bus-bars, fixed in a distribution board of hard

wood or metal case are connected to the supply main through a linked switch so that the installation can

be switched off as a whole from both the poles of supply if required. A fuse is inserted in the + ve or

phase pole of each circuit so that each circuit is connected up through its own particular fuse.

In large buildings, however, if only one distribution board were used, some of the points would be at a

considerable distance from it and in such cases it is advisable to employ sub-distribution boards either to

save cable or to prevent too great voltage drop at the more distant points (lamps or fans or other

appliances). In such cases main distribution board controls the circuit to each sub-distribution board

from which the sub-circuits are taken, as shown in fig. 3.2


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The number of circuits and sub-circuits are decided as per number of points to be wired and load to be

connected to the supply system. For determination of load of an installation the following ratings maybe

assumed unless the values are known or specified.

a) Fluorescent lamps40 watts.

b) Incandescent lamps, fans, and socket outlets60 watts.

c) Power socket-outlets1,000 watts.

d) Exhaust fansas per capacity of exhaust fans.

There are number of methods of installing a wire system.

Cleat wiring

Casing Wiring

T.R.S. Wiring

Metal Sheathed Wiring

Conduit Wiring

PVC Conduit Wiring

Generally, for wiring in the house 20 SWG wire is used and for Earthing 14 SWG is used.

HOUSE WIRE LAYOUT- Two wire from RSEB Pole bring 230 volt A.C. to our house. Our house is

Phase (P) and other is neutral.

ENERGY METER- It may be disk type, Conduction Meter or Electronic Meter.

SOCKET- Socket has three types of terminals-

Neutral,

Phase ,

Earthing

Earthing is of big size and other two are same.

M.C.B. (Miniature Circuit Breaker)normally, in House wiring, 2 Pole M.C.B. is used. As we know

the fuse and M.C.B. are in fact is used to isolate a system from supply in case of:-

Over load

Short circuit

EARTHINGWe know that Earthing is provided for the safety of both, Human Beings and Equipments.

It is of two types-

Plate earthing

Pipe earthing


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FACTOR AFFECTING EARTH RESISTANCEThe earth electrode resistance depend on electrical

resistivity of soil which in turn depends upon-

Nature of soil

Extent of moisture

Presence of suitable salt in moisture

EARTH ELECTRODEIt is of two types-

rod and pipe electrode

plate electrode

CIRCUIT DIAGRAM

F ig 3.3 Circuit Diagram of House Wir ing with Earth ing

OBSERVATION TABLE

S. No. Devices Switches

1 Bulb B12 Fan B2

3 Tube Light B3

4 5 Amp,3 pin socket B4

RESULTWe make connection and get result as shown in Observation Table.

PRECAUTIONS

No any connections should be loosed.

Do not touch any wire.

Do not keep any joint open.

Use M.C.B. and switches of proper current rating.


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EXPERIMENT # 3(B)

OBJECT To wiring for a lamp to be controlled from two positions (stair-case wiring).

APPARATUS - REQUIRED

Sr. No.Apparatus Rating

Type Quantity

1. Lamp Holder 6Amps, 250 volts 1

2. Lamp 100 Watts,15 Watts 1

3. Switches( Two-way) 5 Amps, 250 Volts 2

4. Connecting Leads

-

- As Reqd.

5. Screw Driver - - As Reqd.

THEORY

STAIR-CASE wiring is a special type of wiring ,which is different from ordinary wiring due to

field of application.

In staircase wiring ,bulb used for lightening the staircase can be switched ON and OFF from both

sides, upstairs and downstairs , for this kind of arrangement circuit is shown in fig. When both the

switches are in up position bulb gets neutral at both points hence it will be in OFF-STATE . Now

if position of any of the switch is changed the phase is applied to one end of bulb and it

becomes ON. Now if the position of other switch is also changed, the bulb becomes OFF as

phase gets applied at both the ends of bulb. Now if again position of any off switch is changed

,the bulb becomes ON again.

A Different arrangement for stair-case wiring is shown in fig. In fig.3.4 neutral(N) is directly

connected to the bulb and for phase(P) straight connections are made in the two switches.

In cross connection, if both switches have same position( i.e. either at A or either at B) lamp

would not glow. Whereas in straight connection; if both switches have same position of either

switch has been changed, lamp change its position.

Stair case wiring


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F ig 3.4 Cir cuit Di agram of Stair case wir ing

OBSERVATION- TABLE

RESULT

We studies about the house wiring and made connections for different house wiring

application viz. stair case wiring and a room wiring.

PREACAUTIONS

No any connections should be loosed.

Do not touch any wire.

Do not keep any joint open.

Use M.C.B. and switches of proper current rating

POSITION OF

SWITCHES &

LAMPS

POSITION

OF SWITCHES

& LAMPS

POSITION

OF SWITCHES

& LAMPS

POSITION

OF SWITCHES

& LAMPS

S1 S2 LAMP S1 S2 LAMP S1 S2 LAMP S1 S2 LAMP


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VIVA QUESTIONS

1.What is MCB

2.What is full form of MCB?

3.What is use of MCB in house wiring?

4.What is one way switch?

5.What is two way switches?

6.What is energy meter?

7.Why is use of energy meter in house wiring?

8.What is the application of energy meter?

9. What is the connection of energy meter?

10.How to draw the symbol of one way switch?

11.What is the symbol of energy meter?

12.Why the design of earthing point is long in 3 pin top?

13.Where two way switch is used?

14.Where staircase wiring is used?

15.What is the use of earthing wire in house wiring?


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EXPERIMENT # 4 (A)

OBJECT To study the construction and basic working of ceiling fan and connections of ceiling

fan with regulator.

APPRATUS

S. No. Name Range/Rating Type Quantity

1 Fan motor(stator/rotor)

60W,0.6A,350rpm,23010%volts

1- squirrel cageinduction motor

1

2 Capacitor 2.5MFD5%, 440V AC

50Hz, Max. Temp.85

+-| (-- 1

3 Fan assembly(Canopy/suspension

rob, blades etc.)

- - 1

4 Fan regulator (0 -350)rpm Resistance/electronics 1/1

5 Test lamp 200W 1

6 Different tools - - As per

requirement

7 Multi meter Analog/digital - 1

8 Voltmeter (0 -300)volts Moving coil 1

9 Ammeter (01) Amp. Moving coil 1

10 Connecting leads - - As per

requirement

THEORY

CEILING FAN

A ceiling fan is a propeller blade and having two or more blades, directly driven by an electric motor and

intended for use with free inlet & outlet. It is provided with a device for suspension from ceiling of a

room so that the blades rotate in a plane to give uniform air circulation in the room.

According to the electric motor used, ceiling fans can be classified as follows:

1. DC FANS: DC fans uses series motors and generally used where dc supply is easily available as

like trains, buses etc.

2. AC FANS: AC fans are most commonly used domestic devices, which are generally known.

AC fans use single phase squirrel cage induction motor.


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DIFFERENT PARTS OF CEILING FAN

1. Motor

2. Capacitor

3. Blades

4. Canopy

5. Ball-bearings

6. Speed regulators

F ig 4.1 Construction Diagram of ceil ing fan

Construction

Main parts of a ceiling fan are

(a) Winding

(b) Capacitor &

(c) Regulator

Winding of the motor can be done manually or by automated machine. Regulator may be electronic type

or resistance type. Electronic type regulator has negligible power loss and compact size. But in the case

of resistance type, resistances are connected in series with the circuit; this may cause power loss as heat.

In table fan one permanent split capacitor run (PSC) motor is the heart of a fan. This motor consists of

two windings one as starting winding and other as running winding.

Starting winding of this motor has high resistance and low reactance but running winding has low

resistance and high reactance. One capacitor is connected in series with the starting winding and whole

of this circuit is put in parallel across running winding. In the case of ceiling fan these two windings are

placed in stator in the inner side of the fan.

Rotor has no winding; it is the outer body of the fan. Ceiling fan motor operates just in opposite manner

as compared to general motor. That is actual rotor of the motor is blocked and the stator is free to rotate.


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So ceiling fan runs in anticlockwise direction. At the same time table fan motor is operated as normal

case and so it runs in clockwise direction. Capacitor connected in series with the starting winding should

be value 2.5 microfarad. Pyranel insulated foil paper capacitor is using for this purpose. It helps to

provide a split phase effect from single phase AC supply.

F ig 4.2(a) Ceil ing fan winding Diagram F ig 4.2(b) Circuit diagram of ceil ing fan

WORKING PRINCIPAL

AC ceiling fan has single phase induction motor, which comprises two distributed windings stator and a

rotor (squirrel cage) when current is given to the motor , the magnetic field is experience a force in the

rotor to move it right angle to the field at the blades attached with the rotor displace the air.

OBSERVATION TABLE

Test for Condition of lamp Test result

1. Running winding

2. Starting winding

3. Earth test of fan

4. Capacitor(a)Open test(b)Short test(c)Continuity test

RESULT

We studied about the ceiling fan and performed various testing and get result as shown in observation

table.


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PRECAUTION

1. Do not touch any live wire or contact.

2. Make the proper connection as given in circuit diagram and it should checked by lab in-charge

before switch ON the supply.

3. Save the winding of fan for any damage.

4. Handle the equipments carefully, which are used in the experiment.

5. Use only 200W lamp for testing purpose for saving any damage to windings due to high current.


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EXPERIMENT # 4 (B)

OBJECT To study construction and basic working of single phase and three phase inductionmotor. Also To control the speed of Single Phase induction motor through auto transformer.

APPARATUS

S.

No.Name Type Range Quantity

1. Single phase

Induction Motor

Squirrel Cage 230V, 2HP 1500 rpm 50 Hz 1

2. Three phase

Induction Motor

Squirrel Cage 415V 50 Hz2 HP 1500 rpm 1

3. Voltmeter M I (0-600 V)/(0-300 V) 1/1

4. Ammeter M I 2A/5A 1/1

5. Auto

Transformer

Single Phase 230V/(0-270)V 1

6. Tachometer Digital 0-2000rpm 1

7. Watt meter Dynamometer 10/20A,300/600V,1800W/2000W 2

THEORY

Single Phase Induction MotorMost small power (generally below 2 kW) induction machines have to operate with single-phase a.c.

power supplies that are readily available in homes, and remote rural areas. When power electronics

converters are used three phase a. c. output is produced and thus three phase induction motors may still

be used. However, for constant speed applications (the most frequent situation), the induction motors

are fed directly from the available single-phase a. c. power grids. In this sense, we call them single phase

induction motors. To be self-starting, the induction machine needs a travelling field at zero

speed. This in turn implies the presence of two windings in the stator, while the rotor has a standardsquirrel cage. The first winding is called the main winding while the second winding (for start,

especially) is called auxiliary winding. Single phase IMs may run only on the main winding once they

started on two windings. A typical case of single phase single-winding IM occurs when a three IM ends

up with an open phase. The power factor and efficiency degrade while the peak torque also decreases

significantly. Thus, except for low powers (less than kW in general), the auxiliary windingis active

also during running conditions to improve performance. Three types of single-phase induction motors

are in use today:


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F ig 4.3(a)Circuit Diagram of slipt phase induction motor(b) phasor Diagram of sl ipt phase induction motor

3.2 SPLIT-PHASE INDUCTION MOTORS

The split phase induction motor has a main and an auxiliary stator winding displaced by 90 or up to 110-

120 degrees (Figure 4.3a). The auxiliary winding has a higher ratio between resistance and reactance, by

designing it at a higher current density, to shift the auxiliary winding current I ahead of main winding

current I (Figure 4.3b). The two windings-with a 90 space displacement and a 20-30 current time

phase shift-produce in the air gap a magnetic field with a definite forward travelling component (from m

to a). This travelling field induces voltages in the rotor cage whose currents produce a starting torque

which rotates the rotor from m to a (clockwise on Figure 4.3). Once the rotor catches speed, the starting

switch is opened to disconnect the auxiliary winding, which is designed for short duty. The starting

switch may be centrifugal, magnetic, or static type. The starting torque may be up to 150% rated torque,

at moderate starting current, for frequent starts long-running time applications. For infrequent starts and

short running time, low efficiency is allowed in exchange for higher starting current with higher rotor

resistance. During running conditions, the split-phase induction motor operates on one winding only and

thus it has a rather poor power factor. It is used below 1/3 kW, generally, where the motor costs are of

primary concern.

3.3 CAPACITOR INDUCTION MOTORS

Connecting a capacitor in series with the auxiliary winding causes the current in that winding I to lead

the current in the main winding Ia by up to 90. Complete summarization of the two windings m. m. f.

for given slip may be performed this way. That is a pure travelling air gap field may be produced either

at start (S = 1) or at rated load (S = S) or somewhere in between. An improvement in starting and


32/151


running torque density, efficiency and especially in power factor is brought by the capacitor presence.

Capacitor motors are of quite a few basic types:

3.4 SHADED POLE INDCUTION MOTORShaded pole motors have only one main winding and no start winding. Start winding means of design

that ring a continuous copper loop around a small portion of the motor pole. This shadedthat portion if

the pole, causing the magnetic filed in the shaded area to lag behind the field in the un shaded area.

Shaded pole motor impractical For most industrial or commercial use.

Three Phase Induction Motor

Three phase induction motor consists of silicon steel slotted core in which three phase copper wire

winding is done and connection brought out on terminal box. The motor is also made of silicon steel

stampings core slotted in which copper or aluminum bars are inserted and shorted by copper or

aluminum short circuiting rings on both sides.

The body is made of cast iron on which channel given by a fan fitted on the shaft of the motor on rear

side. The fan is covered by a sheet steel cowl. The connections of stator winding is made inter is star or

in delta. Low HP motors are connected in star, medium and high HP motors are connected in star to

delta or delta to star.

The three phase motor works on mutual induction principle. The three phase stator when supplied with

three phase acts as primary produces three rotating magnetic field links the rotor induces emf in rotor

and the current circulates in rotor bars through short circuiting rings, then force is exerted on rotor

conductors and the rotor rotates in the direction of rotation of the magnetic field and so the three phase

induction motor is hence self starting.

The directions of rotation of three phase rotating magnetic field can be reversed by inter changing any

two phases of the supply.


33/151


DIAGRAM

F ig 4.4 Cross section of Single phase I nduction motor

PROCEDURE

1. Make connection as shown in fig

2. Put input voltage at Zero

3. Now slowly vary input voltage and measure the speed by tachometer

4. Record the value of speed at various voltage

OBERVATION TABLE

S. No Input Voltage Speed(rpm)1 50

2 100

3 150

4 175

5 200

6 230

RESULTStudy the construction and basic working of ceiling fan, single phase induction motor and

three phase squirrel cage induction motor. Connect ceiling fan along with regulator and single phase

induction motor through auto-transformer to run and vary speed.


34/151


PRECAUTIONS

Connection should be right and tight

Main switch , starter and motor should be earthed

Use of proper range of voltmeter and ammeter

Dont touch the shaft of the running motor


35/151


VIVA QUESTIONS

1.What is motor?

2.How many types of motor are available?

3.What is the working principle of induction motor?

4.Induction motors are of how many types?

5.What is double revolving field theory?

6.Why single phase induction motors are not self starting?

7.What is the difference between stator and rotor?

8. What is armature winding and why it is used?

9. Which method use for speed control in induction motor?

10.Why is use of regulator?

11.What is working of capacitor in fan?

12.Which is the type of winding in ceiling fan?

13.How many winding s are available in ceiling fan?

14. Which winding have high resistance in ceiling fan?

15.Starting winding is high resistance in ceiling fan why?


36/151


EXPERIMENT # 5(A)

OBJECT

(A) Study the construction and connection of single phase transformer and auto-transformer.Measure input and output voltage and fin turn ratio.

APPARATUS

S. No. Name Rating Type Quantity

1 Single phase transformer 2Kva,230V/(0-400)v --- 1

2 Single phase auto transformer 1Kva,230/(0-270)V --- 1

3 Voltmeter (0-300)/(0-600) --- 1/1

4 Connecting leads --- As per require

THEORY

1. Types and Construction of Transformers

Types of cores for power transformer (both types are constructed from thin laminations electrically

isolated from each otherminimize eddy currents)

F ig 5.1(a) Core type T/F

i) Core Form: a simple rectangular laminated piece of steel with the transformer windings wrapped

around two sides of the rectangle.

Fig 5.1(b) Shell type T/F

ii) Shell Form: a three legged laminated core with the windings wrapped around the centre leg.


37/151


a

N

N

tv

tv

s

p

s

p

The primary and secondary windings are wrapped one on top of the other with the low-voltage winding

innermost, due to 2 purposes:

i) It simplifies the problem of insulating the high-voltage winding from the core.

ii) It results in much less leakage flux

Types of transformers:

i) Step up/Unit transformersUsually located at the output of a generator. Its function is to step up

the voltage level so that transmission of power is possible.

ii) Step down/Substation transformers Located at main distribution or secondary level

transmission substations. Its function is to lower the voltage levels for distribution 1st

level

purposes.

iii)Distribution Transformerslocated at small distribution substation. It lowers the voltage levels

for 3ndlevel distribution purposes.

iv)Special Purpose Transformers - E.g. Potential Transformer (PT) , Current Transformer (CT)

2. The Ideal Transformer

1. Definitiona lossless device with an input winding and an output winding.2. Figures below show an ideal transformer and schematic symbols of a transformer.

Fig 5.3 (a) ideal transformer Fig5.3 (b) schematic symbols of a transformer

3. The transformer has Npturns of wire on its primary side and Nsturns of wire on its secondary

sides. The relationship between the primary and secondary voltage is as follows:

4.

Where ais the turns ratio of the transformer


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atiti

s

p 1

The relationship between primary and secondary current is:

Np ip(t) = Ns is(t)

5. Note that since both types of relations give a constant ratio, hence the transformer only changes

ONLY the magnitude value of current and voltage. Phase angles are not affected.

6. The dot convention in schematic diagram for transformers has the following relationship:

i) If the primary voltageis +ve at the dotted end of the winding wrt the un dotted end, then the

secondary voltage will be positive at the dotted end also. Voltage polarities are the same wrt

the dots on each side of the core.

ii) If the primary currentof the transformer flows intothe dotted end of the primary winding,

the secondary current will flow outof the dotted end of the secondary winding.

Power in an Ideal Transformer1. The power supplied to the transformer by the primary circuit:

Pin= Vp Ip cos p

Where p= the angle between the primary voltage and the primary current. The power supplied by

the transformer secondary circuit to its loads is given by:

Pout= Vs Is cos s

Where s= the angle between the secondary voltage and the secondary current.

2. The primary and secondary windings of an ideal transformer have the SAME power factor

because voltage and current angles are unaffected p - s =

3. How does power going into the primary circuit compare to the power coming out?


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cospp

out aIa

VP

dt

deind

N

i

i

1

N

dt

dNeind

Pout = VsIscos

Also, Vs= Vp/a and Is= a Ip

So,

Pout = VpIpcos = Pin

The same idea can be applied for reactive power Q and apparent power S.

Output power = I nput power

3. Theory of Operation of Real Single-Phase Transformers

Ideal transformers may never exist due to the fact that there are losses associated to the operation of

transformers. Hence there is a need to actually look into losses and calculation of real single phase

transformers.

Assume that there is a transformer with its primary windings connected to a varying single phase voltage

supply, and the output is open circuit.

Right after we activate the power supply, flux will be generated in the primary coils, based uponFaradays law,

where is the flux linkage in the coil across which the voltage is being induced. The flux linkage is

the sum of the flux passing through each turn in the coil added over all the turns of the coil.

This relation is true provided on the assumption that the flux induced at each turn is at the same

magnitude and direction. But in reality, the flux value at each turn may vary due to the position of the

coil itself, at certain positions, there may be a higher flux level due to combination of other flux from

other turns of the primary winding. Hence the most suitable approach is to actually average the flux level

as

Hence Faradays law may be rewritten as :


40/151


dttvN PP)(

1

LPMP

The voltage ratio across a Transformer

Fig5.4Circuit Di agram of transformer

The voltage source is vp(t), how will the transformer react to this applied voltage?

Based upon Faradays Law, looking at the primary side of the transformer, we can determine the average

flux level based upon the number of turns; where,

This relation means that the average flux at the primary winding is proportional to the voltage level atthe primary side divided by the number of turns at the primary winding. This generated flux will travel

to the secondary side hence inducing potential across the secondary terminal.

For an ideal transformer, we assume that 100% of flux would travel to the secondary windings.

However, in reality, there are flux which does not reach the secondary coil, in this case the flux leaks out

of the transformer core into the surrounding. This leak is termed as flux leakage.

Taking into account the leakage flux, the flux that reaches the secondary side is termed as mutual flux.

Looking at the secondary side, there is similar division of flux; hence the overall picture of flux flow

may be seen as below:

Primary Side:

P = total average primary flux

M = flux component linking both primary and secondary coils

LP = primary leakage flux

For the secondary side, similar division applies.


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dt

dN

dt

dN

dt

dNtv LPP

MP

PPP

)(

)()()( tetetv LPPP

dt

dNte M

PP

)(

S

SM

P

P

N

te

dt

d

N

te )()(

aN

N

te

te

S

P

S

P

)(

)(

Hence, looking back at Faradays Law,

Or this equation may be rewritten into:

The same may be written for the secondary voltage.

The primary voltage due to the mutual flux is given by

And the same goes for the secondary (just replace P with S)

From these two relationships (primary and secondary voltage), we have

Therefore,

Magnetization Current in a Real transformer

Although the output of the transformer is open circuit, there will still be current flow in the primary

windings. The current components may be divided into 2 components:

1) Magnetization current, iMcurrent required to produce flux in the core.

2) Core-loss current, ih+ecurrent required compensating hysteresis and eddying current losses.

We know that the relation between current and flux is proportional since,

F Ni R

Ri

N

Therefore, in theory, if the flux produce in core is sinusoidal, therefore the current should also be a

perfect sinusoidal. Unfortunately, this is not true since the transformer will reach to a state of near

saturation at the top of the flux cycle. Hence at this point, more current is required to produce a certain

amount of flux.

SINGLE PHASE AUTO TRANSFORMER

An auto transformer is one winding transformer in which a part of winding is common to

both voltage and low voltage sides. Consider a single winding ABC. The terminals A and C are the high


42/151


voltage terminals the low voltage terminals are B and C is a suitable tapping point. The portion BC of

the full winding ABC is common to both high-voltage and low voltage sides. The winding BC is called

the common winding and the smaller winding AB is called the series winding because it is connected in

series with common winding.

A step down auto transformer is one in which the primary voltage is greater than the secondary voltage.

the source voltage v(h) is applied to the full winding ABC and the load is connected across the

secondary terminals BC .this arrangement is called the step down autotransformer. Since the Trans

former winding are physically connected a different terminology is used for the auto transformer than for

other types of transformer. In an auto transformer there are two voltage ratios namely circuit voltage

ratio and winding voltage ratio. The circuit voltage ratio is given as-

VH/VL = TH/TL= a

Fig5.5Circuit Di agram of transformer

The quantity a also called transformation ratio of the auto transformer it is seen form equation that a is

always greater than 1.

(1) ADAVANTAGES OF AUTO TRANSFORMER

* An auto transformer is smaller in size and cheaper than a two winding transformer of same

output.

* An auto transformer has higher efficiency since core loss and ohmic losses are smaller.

* An auto V has variable output voltage when a sliding contact is used for the secondary.

(2) DISADAVANTAGES OF AUTO TRANSFORMER

* There is direct connection between the high voltage and low voltage side. if there is open

circuit in winding BC the full primary voltage would be applied to the secondary. This high voltage may

cause serious damage to the equipment connected on the secondary side.

(3) APPLICATIONS OF AUTO TRANSFORME

* Auto transformer are used for obtaining continuously variable ac voltage.

* They are used for interconnections of power system of different voltage levels.

* they are applied for boosting of ac mains voltage by a small amount.

* Auto transformer are used for starting the induction motors and synchronous motors.

6. MEASUREMENT OF INPUT AND OUTPUT VOLTAGE


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For measurement of input and output voltage of single phase transformer makes connection. Take

readings of voltmeter at various tap positions. Similarly for measurement of input and output voltage of

auto transformer, make connection. Take reading of voltmeter by varying knob of auto transformer and

find turn ratio.

OBSERVATION TABLE

For Single Phase Auto Transformer

S.No. VH (VHV)(VOLT) VL (VLV)(VOLT) TURN RATIO

1.

2.

3.

4.For Single Phase Transformer

S.No. V (VOLT) Vs (VOLT) TURN RATIO

1.

2.

3.

4.

RESULTRelations between line current and phase current for different connection has been observed.

PRECAUTIONS

1. All connection must be tight.

2. Get the circuit connections checked by the teacher before performing the experiment.

3. Power to the circuit must be switched on in the presence of the teacher.

4. Get the experimental readings checked by the teacher.

5. Dont touch directly the live parts of equipment andcircuit.

6. Wear leather shoes in the lab.


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EXPERIMENT # 5(B)OBJECT Study the construction of a core type three phase transformer. Perform star and delta

connection on a 3-phase transformer and find relation between line and phase voltage.

APPARATUS REQUIRED

S. No. Name of apparatus Type Range Quantity

1 Voltmeter Digital (0-500)V 03

2 Ammeter Digital (0-5)A 02

3 3 phase Transformer Delta-star 3 KVA,440/440 V 01

4 3 phase Auto Transformer 8/16 A,415/470 V 01

THEORY

Delta/Delta ConnectionThe ratio of primary to secondary line voltages remains equal to the ratio of

transformation a. The main advantage of this connection lies in that the system can still operate on

58%of its rated capacity even in case of failure of one of the transformers. The remaining two

transformers work in open delta or V. This connection is favored for voltages below 50 KV.

F ig. 5.6 Delta/Delta connection

Delta/Star Connection: This gives a higher secondary voltage for secondary for transmission purposes

than connections with delta secondaries without increasing the strain on the insulation of the

transformers. It is the connection commonly used at the generating end of transmission lines. The starneutral is generally grounded.

F ig. 5.7 Delta/Star connection


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Star/Star ConnectionThis permits the neutral points of both primary and secondary 3 phase circuits.

When the primary neutral is not connected to the source neutral, it is necessary to use delta connected

tertiary winding in order to avoid imbalance in the system.

Fig. 5.8 Star/Star connection

Star/Delta Connection This connection is commonly used at the receiving ends of high voltage

transmission lines.

F ig. 5.9 Star/Delta connection

PROCEDURE

(a)Connect the circuit as shown in figure.

(b)Ensure that variac is at its minimum position.

(c)Switch ON the supply by closing switch and apply the rated voltage slowly by increasing

the position of variac.

(d)Note down the reading of Ammeters & Voltmeters.

(e)Now decrease the applied voltage up to zero by decreasing the position of variac.

(f) Switch OFF the supply.


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OBSERVATION TABLE

Type of

Connection

PRIMARY SIDE SECONDARY SIDE

Iline Iphase Vline Vphase Iline Iphase Vline Vphase

Star/Star

Star/Delta

Delta/Star

Delta/Delta

RESULTS We has studied about the construction, various connections of 3- transformers and

obtains the line and phase voltages on both sides (primary and secondary) of the transformer.

PRECAUTIONS

All connection must be tight.

Get the circuit connections checked by the teacher before performing the experiment.

Power to the circuit must be switched on in the presence of the teacher.

Get the experimental readings checked by the teacher.

Dont touch directly the live parts of equipment and circuit.

Wear leather shoes in the lab.


47/151


VIVA QUESTIONS

1. What is transformer?

2. On which principle Transformer works?

3. What is turn ratio of transformer?

4. Why core of transformer is laminated?

5. Which type of material used for making of core of transformer?

6. What is auto transformer?

7. What is the difference between auto transformer and two winding transformer?

8. Transformers are of how many types?

9. What is difference between core type and shell type transformer?

10. What is relation between phase current and line voltage in - connection?

11. What is relation between phase current and line current in star connection?

12. What is emf equation of transformer?

13. What are the different types of losses in transformer?

14. What is eddy current?

15. What is hysteresis loss?


48/151


EXPERIMENT # 6(A)

OBJECTIdentification, testing and applications of various resistors, inductors, capacitors, PN-

diode, Zener diode, Photo diode.APPARATUS

(i)Different types of resistors, capacitors and inductors.

(ii) Digital/Analog Multi meter

THEORY

RESISTANCE The electrical resistanceof anelectrical element measures its opposition to the passage

of an electric current;the inverse quantity is electrical conductance, measuring how easily electricity

flows along a certain path. Electrical resistance shares some conceptual parallels with the mechanical

notion of friction.The SI unit of electrical resistance is the ohm (), while electrical conductance is

measured inSiemens (S).

An object of uniform cross section has a resistance proportional to itsresistivity and length and inversely

proportional to its cross-sectional area. All materials show some resistance, except forsuperconductors,

which have a resistance of zero.

The resistance of an object is defined as the ratio of voltage across it to current through it:

F ig. 6.1 Resistor

For a wide variety of materials and conditions, the electrical resistance R is constant for a given

temperature; it does not depend on the amount of current through or the potential difference (voltage)

across the object. Such materials are called Ohmic materials. For objects made of ohmic materials the

definition of the resistance, with R being a constant for that resistor, is known asOhm's law.

In the case of a nonlinear conductor (not obeying Ohm's law), this ratio can change as current or voltage

changes; the inverse slope of a chord to anIV curve is sometimes referred to as a "chordal resistance"

or "static resistance".

DC resistance
http://en.wikipedia.org/wiki/Electrical_elementhttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/International_System_of_Unitshttp://en.wikipedia.org/wiki/Ohmhttp://en.wikipedia.org/wiki/Omegahttp://en.wikipedia.org/wiki/Omegahttp://en.wikipedia.org/wiki/Omegahttp://en.wikipedia.org/wiki/Siemens_%28unit%29http://en.wikipedia.org/wiki/Resistivityhttp://en.wikipedia.org/wiki/Superconductorhttp://en.wikipedia.org/wiki/Constant_%28mathematics%29http://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Ohm%27s_lawhttp://en.wikipedia.org/wiki/I%E2%80%93V_curvehttp://en.wikipedia.org/wiki/I%E2%80%93V_curvehttp://en.wikipedia.org/wiki/I%E2%80%93V_curvehttp://en.wikipedia.org/wiki/I%E2%80%93V_curvehttp://en.wikipedia.org/wiki/Ohm%27s_lawhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Constant_%28mathematics%29http://en.wikipedia.org/wiki/Superconductorhttp://en.wikipedia.org/wiki/Resistivityhttp://en.wikipedia.org/wiki/Siemens_%28unit%29http://en.wikipedia.org/wiki/Omegahttp://en.wikipedia.org/wiki/Ohmhttp://en.wikipedia.org/wiki/International_System_of_Unitshttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Electrical_element


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The resistance of a given resistor or conductor grows with the length of conductor andspecific resistivity

of the material, and decreases for larger cross-sectional area. The resistance R and conductance G of a

conductor of uniform cross section, therefore, can be computed as

where is the length of the conductor, measured in meters [m], A is the cross-section area of the

conductor measured insquare meters [m], (sigma)is theelectrical conductivity measured inSiemens

per meter (Sm-1), and (rho)is theelectrical resistivity (also calledspecific electrical resistance) of the

material, measured in ohm-meters (m). Resistivity is a measure of the material's ability to oppose

electric current. For purely resistive circuits conductance is related to resistanceRby:

G=1/R

For practical reasons, any connections to a real conductor will almost certainly mean the current density

is not totally uniform. However, this formula still provides a good approximation for long thin

conductors such as wires.

AC resistance

A wire carrying alternating current has a reduced effective cross sectional area because of theskin effect.

Adjacent conductors carrying alternating current have a higher resistance than they would in isolation or

when carrying direct current, due to theproximity effect.Atcommercial power frequency,these effects

are significant for large conductors carrying large currents, such asbus bars in anelectrical substation,[3]

or large power cables carrying more than a few hundred amperes.

When an alternating current flows through the circuit, its flow is not opposed only by the circuit

resistance, but also by the opposition of electric and magnetic fields to the current change. That effect is

measured by electrical reactance. The combined effects of reactance and resistance are expressed by

electrical impedance.

Measuring resistance

An instrument for measuring resistance is called anohmmeter.Simple ohmmeters cannot measure low

resistances accurately because the resistance of their measuring leads causes a voltage drop that

interferes with the measurement, so more accurate devices usefour-terminal sensing.
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Temperature dependence

Near room temperature, the electric resistance of a typical metal increases linearly with rising

temperature,while the electrical resistance of a typical semiconductor decreases with rising temperature.

The amount of that change in resistance can be calculated using thetemperature coefficient of resistivity

of the material using the following formula:

Where Tis its temperature, T0is a reference temperature (usually room temperature), R0is the resistance

at T0, and is the percentage change in resistivity per unit temperature. The constant depends only on

the material being considered. The relationship stated is actually only an approximate one, the true

physics being somewhat non-linear, or looking at it another way, itself varies with temperature. For

this reason it is usual to specify the temperature that was measured at with a suffix, such as 15and the

relationship only holds in a range of temperatures around the reference.

Fig. 6.2: Temperature character istics of resistance

INDUCTANCE AND INDUCTOR

I. Elementary Characteristics

The coil in the figure simulates an inductor. The main issue is how the magnetic field lines go across the

inductor (lines with arrows). There is some magnetic field at the top bottom of the coil too.

F ig. 6.2 Elementary character istics
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The current I going through the inductor generate a magnetic field which is perpendicular to I. The

Magnetic Field H is given by the loops that surround the current I. The direction of the Magnetic Field

is given by the arrows around the loops. If the current was to flow in the opposite direction the Magnetic

Field arrows would be reversed. For a practical display of this phenomena see: Magnetic field on wire.

F ig. 6.3 Magnetic fi eld on wi re

It is the Magnetic Field which contains the current through the coil which by the principle called Self-

Induction will induce a voltage V. More specifically speaking, the voltage V across the inductor L is

given by: V = /T which reads the voltage V is caused by the change in flux over the

correspondent change in time, but since the change in flux is given by the inductance L and the change

in current across the coilI, the voltage V becomes:

V = L*I/T (electrical definition for inductance)

On the other hand the physical definition of inductance L is given by:

L = N2

* A/l (physical definition for inductance)

where stands for the relative ease with which current flows through the inductor or Permeability of the

medium. N stands for the number of turns in the coil, A stands for its cross-sectional area, and the

length of the coil is given by l. Hence this formula tells us that the more number of turns the larger the

inductance (i.e.: current can be contained better), also the larger the cross-sectional area the larger the

inductance (since there is more flux of current that can be contained) and the longer the coil the smaller

the inductance (since more current can be lost through the turns). L is also proportional to ,since the

better the permeability current will flow with more ease.Inductance and Energy

By containing the current via the magnetic field the inductor is capable of storing Energy. A

Transformer such as the one on the Figure will certainly remind us of the ability of storing Energy

associated with Inductors. Whereas for a capacitor the Energy stored depends on the Voltage across it,

for the inductor the Energy stored depends on the current being held, such that:

W = 1/2*L* I2

where W stands for the energy on the inductor.

Basic Inductor Circuit


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Fig. 6.4 Basic inductor ci rcui t

The electrical parameters V and L (the inductance -measured in Henrys-H - review DC Basics or go

to are given. The current I is implicitly given by the relationship: V = Ldi/dt

In a similar case as with the basic capacitor circuit we are implying that at time 0 a switch closes

connecting the battery to the coil and the inductor starts to get charged. Also, in all real cases there will

be a small resistance in series with the inductor, but we will get to this case in the discussion of R-L

circuits.

At a specific point of time the voltage across the inductor is expressed by V = Ldi/dtwhich is basically

the electrical definition of inductance, except that since we are just focusing at a point in time and not at

an interval of time delta = T we will need to use the termdt and similarly for the current di instead

of I. The electrical definition still holds, since all we are saying is that the flux or change i n current

over time times the inductance is the Induced Voltage across the Inductor.

CAPACITOR

A capacitor is apassiveelectrical component that can storeenergy in theelectric fieldbetween a pair of

conductors (called "plates"). The process of storing energy in the capacitor is known as "charging", and

involves electric charges of equal magnitude, but opposite polarity, building up on each plate. A

capacitor's ability to store charge is measured by itscapacitance,in units offarads.

Capacitors are often used inelectric andelectronic circuits asenergy-storage devices. They can also be

used to differentiate between high-frequency and low-frequencysignals.

F ig. 6.5 Capacitor
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Theory of Operation

F ig 6.6 Parall el-Plate capacitor

Charge separation in a parallel-plate capacitor causes an internal electric field. A dielectric (orange)

reduces the field and increases the capacitance.

Fig 6.7 Demonstration of a parall el-plate capacitor

A simple demonstration of a parallel-plate capacitor

A capacitor consists of twoconductors separated by a non-conductive region. The non-conductive region

is called the dielectric or sometimes thedielectric medium. In simpler terms, the dielectric is just an

electrical insulator. Examples of dielectric mediums are glass, air, paper,vacuum, and even a

semiconductordepletion region chemically identical to the conductors. A capacitor is assumed to be

self-contained and isolated, with no netelectric charge and no influence from any external electric field.

The conductors thus hold equal and opposite charges on their facing surfaces, and the dielectric develops

an electric field. InSI units, a capacitance of onefarad means that onecoulomb of charge on each

conductor causes a voltage of onevolt across the device.

The capacitor is a reasonably general model for electric fields within electric circuits. An ideal capacitor

is wholly characterized by a constant capacitance C, defined as the ratio of charge Qon each conductor

to the voltage Vbetween them:

Sometimes charge build-up affects the capacitor mechanically, causing its capacitance to vary. In this

case, capacitance is defined in terms of incremental changes:
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Energy storage

Work must be done by an external influence to "move" charge between the conductors in a capacitor.

When the external influence is removed the charge separation persists in the electric field and energy is

stored to be released when the charge is allowed to return to itsequilibriumposition. The work done in

establishing the electric field, and hence the amount of energy stored, is given by:

LED

A light-emitting-diode (LED) is a semiconductor diode that emits light when an electric current is

applied in the forward direction of the device, as in the simple LED circuit. The effect is a form of

electroluminescence whereincoherent and narrow-spectrum light is emitted from thep-n junction.

LEDs are widely used as indicator lights on electronic devices and increasingly in higher power

applications such as flashlights and arealighting.An LED is usually a small area (less than 1 mm2) light

source, often with optics added to the chip to shape its radiation pattern and assist in reflection. The color

of the emitted light depends on the composition and condition of the semi conducting material used, and

can beinfrared,visible,orultraviolet.Besides lighting, interesting applications include usingUV-LEDsfor sterilization of water and disinfection of devices, and as a grow light to enhancephotosynthesis in

plants.

F ig 6.8 LED
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P-N DIODE

Inelectronics,a diode is a two-terminal device (thermo ionic diodes may also have one or two ancillary

terminals for aheater). Diodes have two activeelectrodesbetween which the signal of interest may flow,and most are used for their unidirectional electric current property. The directionality of current flow

most diodes exhibit is sometimes generically called therectifyingproperty. The most common function

of a diode is to allow an electric current to pass in one direction (called the forward biased condition)

and to block the current in the opposite direc

209 eee labmanual_28 april2012

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