applied physics lab

7/29/2019 Applied Physics Lab

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APPLIED PHYSICS

(GS-113)

LAB MANUAL

DEPARTMENT OF MECHANICAL

ENGINEERING

SWEDISH COLLEGE OF ENGINEERING AND

TECHNOLOGY, WAH CANTT

RIZWAN ALI KHAN

ALI MURAD


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Sr.No Description

1 Introduction to Lab Apparatus

2 Construction and Measurements of DC circuits

3 Introduction to Conductors, Semiconductors and Insulator and their usages.

4 Ohms Law

5 Magnetic field strength

6 Self induction

7Mutual induction

8Lenzs Law and Faraday law

9Magnetic flux detection

10Introduction to oscilloscope

11 To determine the Frequency of AC signals

12B-H curve

13To study the Characteristics of P-N junctions

14 To study the Characteristics of Zener diode

15 To study the Characteristics and Operation of LED

16To study the Characteristics of Varactor and Tunnel Diode


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Objectives

1. Use of Digital Multimeter (DMM)2. Introduction to DC Power Supply

Equipment Required1. Digital Multimeter

2. DC Power Supply

Procedure and Theory:

1. Use of Digital Multimeter (DMM)

How to Measure Resistance:

1. Rotate the knob of digital multimeter from OFF to .

2. Verify that the red lead plugs into the jack and the black lead plugs into theCOM jack.

3. Connect the red and black leads across the resistor.

4. The resulting value will appear on the display.NOTE: The unit for resistance is Ohm (symbol ). The bigger units are KiloOhm (symbol K) and Mega Ohm (symbol M).

How to Make DC Voltage Measurements:

1. Rotate the knob from OFF to V.

2. To switch between AC & DC press SHIFT button once.

Lab # 1 - Introduction to Basic Lab Apparatus


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3. Verify that the red lead plugs into the V jack and the black lead plugs into theCOM jack.

4. To make a measurement, connect the tip of the red lead and the tip of the blacklead across the points where you want to measure voltages (potential difference).A positive meter reading means the point where the red tip is connected is higher

in voltage than the point where the black tip is connected.NOTE: The unit for voltage is the volt (symbol V). Smaller units of voltageare the millivolt (10-3 volt) symbol mV, and the microvolt (10-6 volt) symbolV.

How to Make Current Measurements:

1. Rotate the knob to A.

2. Make sure that the red lead plugs into the A or A.mA jack and the black leadplugs into the COM jack.

3. To switch between AC & DC press SHIFT button once.

4. To make a current measurement, the tip of the red lead and the tip of the blacklead must be inserted in series with the element whose current is to be measured.A positive meter reading means the point where the red tip is connected hascurrent entering it.

NOTE: The unit for current is the ampere (symbol A upper case).Smaller units of current are the milliampere (10-3 ampere) symbol mA, andthe microampere (10-6 ampere) symbol A.

Introduction to DC Power Supply

The power supply has two variable Master and Slave (0 to 30Volts) and one fixed(5Volts) DC voltage source. The variable supply has a current limit which can be setby the user.1. Press the Power On button.

2. If using the variable dc supply, connect the red lead with + and the black leadwith - .

3. The vlotage and current can be set to desired level by rotating the knobs & theresulting value appears on the display.

4. If using the fixed 5 Volts supply, connect red lead with + and black with -.

5. Two variable supplies can be be used in series or parallell combination by usingtracking buttons.


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Lab performed on (date): ___________________________

Signature: ___________________________

Checked by: ____________________________

Marks Awarded: ____________________________Comments:_____________________________________________________________________________________________________________________________________

______________________________________________________________________________________________________________________________________________


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Objectives1. The objective of this experiment is to analyze and construct simple resistive

circuits in DC. The circuits considered here are: resistors in series, resistors inparallel, series-parallel combination, voltage divider, current divider and theWheatstone bridge. This experiment will allow the experimental verification ofthe theoretical values of Req.

Equipment Required

1. Digital Multimeter (DMM)

2. DC Power Supply

3. Wire Stripper

4. Resistors

Theory of Resistive Circuits:

The theoretical analysis of the circuits under study is based on Ohms and Kirchhoffslaws. The main equations relating the electrical parameters of every circuit are presentedbelow.

1. Ohms law. The voltage V(in volts, V) across a resistor is directly proportionalto the currentI(in amperes, A) flowing through it. The constant of proportionalityis the resistanceR (in ohms,).

V=RI (2-1)2. Resistors in series. (See Figure 2-1).

The current throughNelements in series is the same for all of them.

Is =I1 =I2 = . . . . . . =In (2-2)

The voltage across the ith element isRiIi. The sum of the voltages across eachelement is equal to the voltage applied to the entire series combination.

Vs = V1 + V2 + . . . . . . + Vn (2-3)

Equation 2-3 is formulated from Kirchhoffs voltage law.

The equivalent resistance of the series combination is the sum of the individual

resistances. Req = R1 + R2 + . . . . . . + Rn(2-4)

3. Resistors in parallel. (See Figure 2-2).

The voltage acrossNelements in parallel is the same for all of them.

Vs = V1 = V2 = . . . . . . = Vn (2-5)

Lab # 2 - Construction & Measurements in DC CircuitsLab # 2 - Construction & Measurements in DC Circuits


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The current through the ith element is Vi/Ri. The sum of the currents through eachelement is equal to the current provided to the entire parallel combination.

Is = I1 + I2 + . . . . . . +In (2-6)

Equation 2-6 is formulated from Kichhoffs current law.

The reciprocal of the equivalent resistance of the parallel combination is the sumof the reciprocal of the individual resistances.

Neq RRRR

1.....

111

21

++== (2-7)

4. Series-parallel combination. An example of a series-parallel combination circuitis shown in Figure 2-3.The analysis of this type of circuit is accomplished bysubstituting the series (or parallel) combinations by their equivalent resistances,such that the circuit is transformed into a pure parallel (or series)circuit. Once theelectrical parameters (voltage and/or current) have been determined for theequivalent resistances, the voltages and/or currents for the individual resistors inthe series or parallel combinations can be obtained by using these parameters asVs andIs for the corresponding combination.

5. Voltage divider. From Equation 2-3, a series circuit with two resistors will dividethe applied voltage Vs into two voltages V1 and Vo across each resistor. Noticethat Vo is the output of the voltage divider (see Figure 2-4), as it is referenced toground. The proportion in which the input voltage Vs is divided is given by

oV =R2R1

R2Vs

+(2-8)

In order for this circuit to operate as a voltage divider, the output currentIo mustbe zero or very small compared with the current throughR2.

6. Current divider. (See Figure 2-5). From Equation 2-6, a parallel circuit with tworesistors will divide the applied currentIs into two currentsI1 andILthrough eachresistor. The proportion in which the input currentIs is divided is given by

IL =RLR1

R1Is

+(2-9)

7. Wheatstone bridge. Figure 2-6 shows the Wheatstone bridge circuit. The outputof this circuit is the difference of potential across nodes a and b. Notice that it iscomposed of a pair of voltage dividers, therefore, no significant current can bedrawn from the output. The output voltage is given by

abV =

++ R4R3R4

R2R1

R2.Vs (2-10)


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Procedure

This part of the experiment requires assembling the resistive circuits presented in theprevious section and measuring Req from all of them. Refer to the Lab#1 regarding theuse of the equipment and breadboard. These activities allow for a continuingfamiliarization with the use of the equipment.

Assemble following circuit on bread board, calculate and measure their Req values alongits figure.


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Analysis


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This section is intended for the analysis and comparison of the experimental andtheoretical results. Answer all the questions.

1. Calculate the error percentage between the measured and theoretical data andcomplete all the corresponding entries in Tables 2-1 through 2-6. The errorpercentage is given by

%error = 100

th

mth

d

dd

Where dth and dm are the theoretical and measured data respectively.

2. From the above results comment on the three parameters with the highest errorpercentages and the three with the lowest error percentages. Discuss the possiblecauses for error and comment on the overall agreement between the measured andtheoretical data.

Lab performed on (date):______________________

Signature: ___________________________

Checked by: ____________________________

Marks Awarded: __________________________

Comments:_____________________________________________________________________

___________________________________________________________

___________________________________________________________


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Lab # 3 - Introduction to Conductor, Semi-Conductor and

Insulator and their usage

Apparatus: Copper Cables, Diodes, LED, Coaxial Cable, Twisted Pair

All conductors contain electric charges which will move when an electric potentialdifference (measured in volts) is applied across separate points on the material. This flowof charge (measured in amperes) is what is meant by electric current. In most materials,the direct current is proportional to the voltage (as determined by Ohm's law), providedthe temperature remains constant and the material remains in the same shape and state.

Most familiar conductors are metallic. Copper is the most common material used forelectrical wiring. Silver is the best conductor, but is expensive. Gold is used for high-quality surface-to-surface contacts. However, there are also many non-metallicconductors, including graphite, solutions ofsalts, and allplasmas. See electrical

conduction for more information on the physical mechanism for charge flow in materials.

Non-conducting materials lack mobile charges, and so resist the flow of electric current,generating heat. In fact, all non-superconducting materials offer some resistance andwarm up when a current flows. Thus, proper design of an electrical conductor takes intoaccount the temperature that the conductor needs to be able to endure without damage, aswell as the quantity of electrical current. The motion of charges also creates anelectromagnetic field around the conductor that exerts a mechanical radial squeezingforce on the conductor. A conductor of a given material and volume (length cross-sectional area) has no real limit to the current it can carry without being destroyed as longas the heat generated by the resistive loss is removed and the conductor can withstand the

radial forces. This effect is especially critical inprinted circuits, where conductors arerelatively small and close together, and inside an enclosure: the heat produced, if notproperly removed, can cause fusing (melting) of the tracks.

Since all non-superconducting conductors have some resistance, and all insulators willcarry some current, there is no theoretical dividing line between conductors andinsulators. However, there is a large gap between the conductance of materials that willcarry a useful current at working voltages and those that will carry a negligible currentfor the purpose in hand, so the categories of insulator and conductor do have practicalutility.

Thermal and electrical conductivity often go together For instance, most metals are bothelectrical and thermal conductors. However, some materials are practical electricalconductors without being good thermal conductors.
http://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Volthttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Ohm's_lawhttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Saltshttp://en.wikipedia.org/wiki/Plasma_(physics)http://en.wikipedia.org/wiki/Electrical_conductionhttp://en.wikipedia.org/wiki/Electrical_conductionhttp://en.wikipedia.org/wiki/Superconductorhttp://en.wikipedia.org/wiki/Electromagnetic_fieldhttp://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Superconductorhttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Volthttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Ohm's_lawhttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Saltshttp://en.wikipedia.org/wiki/Plasma_(physics)http://en.wikipedia.org/wiki/Electrical_conductionhttp://en.wikipedia.org/wiki/Electrical_conductionhttp://en.wikipedia.org/wiki/Superconductorhttp://en.wikipedia.org/wiki/Electromagnetic_fieldhttp://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Superconductor


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Conductors and Insulators

In a conductor, electric current can flow freely, in an insulatorit cannot. Metals such ascopper typify conductors, while most non-metallic solids are said to be good insulators,having extremely high resistance to the flow of charge through them. "Conductor"implies that the outer electrons of the atoms are loosely bound and free to move throughthe material. Most atoms hold on to their electrons tightly and are insulators. In copper,the valence electrons are essentially free and strongly repel each other. Any externalinfluence which moves one of them will cause a repulsion of other electrons whichpropagates, "domino fashion" through the conductor.

Simply stated, most metals are good electrical conductors, most nonmetals are not.Metals are also generally good heat conductors while nonmetals are not.

Insulators

Most solid materials are classified as insulators because they offer very large resistance tothe flow of electric current. Metals are classified as conductorsbecause theirouterelectrons are not tightly bound, but in most materials even the outermost electrons are sotightly bound that there is essentially zero electron flow through them with ordinaryvoltages. Some materials are particularly good insulators and can be characterized bytheir high resistivity:
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/conins.html#c2http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.html#c5http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/metal.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thercond.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elecur.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/electric/conins.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.html#c5http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.html#c5http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elevol.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html#c2http://hyperphysics.phy-astr.gsu.edu/hbase/electric/conins.html#c2http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.html#c5http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/metal.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thercond.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elecur.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/electric/conins.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.html#c5http://hyperphysics.phy-astr.gsu.edu/hbase/solids/sili.html#c5http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elevol.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html#c2


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Resistivity (ohm m)

Glass 1012

Mica 9 x 1013

Quartz (fused) 5 x 1016

This is compared to the resistivity of copper:

Resistivity (ohm m)

Copper 1.7 x 10-8


Signature: ___________________________

Checked by: ____________________________

Marks Awarded: _____________________________

Comments:____________________________________________________________________________________________________________________________________________________________________________________________________________________


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Objectives

1. To verify Ohms Law by calculating, and then by measuring voltage, current andresistance, and then comparing the calculated and measured results.

2. To verify Ohms Law relationships by increasing one quantity while holding thesecond quantity constant, then measuring and calculating the effect on the thirdquantity.

3. To demonstrate the three power formulae in DC circuits.

Equipment Required

1. Digital Multimeter (DMM)

2. DC Power Supply

3. Wire Stripper 4. Bread Board

5. Resistors: 10, 3.6 k, 4.7 k, 6.8 k, 10 k

Theory of Ohms Law

Ohms Law is the basis of many electrical circuit calculations and is one of themost important theories you will learn: V=IR. The purpose of this experiment is to verifyOhms Law, which in words, simply says that the current through a resistor isproportional to the voltage across it. The way in which we accomplish this is to measure

the voltage across and current through a known resistor for several different pair ofvalues. We can then plot the data on a graph, and if the relationship is truly linear itshould yield a straight line.

When graphing data such as those obtained in this experiment, either the x or y-axiscan be chosen to display the voltage or current values. When the y-axis is chosen as thevoltage axis, and the x-axis as the current axis, we say that we are plotting V versus I. theslope of the line V/I should be equal to the resistance R of the resistor. If on the otherhand, current is plotted on the y-axis, and voltage along the x-axis, then slope of the lineI/V is equal to the conductance G of the resistor. In this experiment you will plot I inmA versus V in volts, and therefore the slope will be the conductance of R. Whenplotting a straight line on a graph such as this, it is important that you draw the best

straight line that you can through the data points.Power in DC Circuit

Electronic devices and circuits require energy to operate. Power is a measure inwatts (W) of the energy in joules (J) consumed by a given device in one second. For aresistor, three equations will yield the power dissipated: P=IV, P=V/R and P=IR. In thisexperiment, you will verify these formulae and plot graphs of the power versus thecurrent, and then power versus the voltage. The resulting curves are parabolas, and the

Lab # 4- Ohms Law


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equations of the curves are called quadratic. By plotting two curves for both 1 k and390 resistors on the same scales and axes, you will be able to see which resistanceconsumes more power for a given current (or voltage).

Procedures

A. Perform the following steps to verify that

RVI =

1. Measure the resistance of the 6.8 k (color-coded value) resistor with the DMM.R1measured =_______________,

2. Connect the circuit in Figure-1.

Figure-1

+

-

15V R1 6.8Kohm

+

-

15V R1 6.8Kohm V

Figure-2

3. Adjust the power supply voltage to 15.0 V using the DMM set on its DC voltagemode.

4. Measure and record the voltage across the R1 resistor. (As shown in Figure-2)

VR1= _____________. Make sure that the voltage across R1 is still 15V.

5. Measure and record the current through R1. (as shown in Figure-3).

IR1 = ________________ VIP= = _______________

15V R1 6.8Kohm

A

Figure-3


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6. Using the measured values of voltage and resistance, calculate the current throughR1 using Ohms Law. Show calculations in the space below.

==R

VI _______________ IR1 = _______________

7. What conclusion can you make from these procedures?

_________________________________________________________________

________

B. Perform

the following steps to verify that

IVR =

1. Connect the same circuit as in Figure 1, except change the value of resistance of3.9 k (color-coded value).

2. Measure and record the voltage across R1 and the current flow through R1.

VR1 = _______________ IR1 = ________________

3. Calculate the resistance of R1 using the measured values of VR1 and IR1 withOhms Law. Show calculation. R1 = _______________

4. Remove R1 from the circuit. Measure and record the resistance of R1 using themultimeter.

R1 = _______________ RIP 2= = _______________


_________________________________________________________________________

C. Perform the following procedures to verify that

RIV =

1. Connect the circuit in Figure 1, except change the resistor to 10 k. (color-coded

value)2. Measure the resistance of this resistor making sure that the resistor is removed

from the circuit. R1 = _______________

3. Reinsert the resistor into the circuit and measure the current through the resistor.

IR1 = _______________

4. Calculate, using Ohms law, the resistor voltage using the measured values ofresistance and current. Show calculation below.


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V = I R = _______________ mA _______________ = _______________V5. Measure the resistor voltage. Record

VR1 = _______________R

VP2

= = _______________


__________________________________________________________________

D. Perform the following procedures to verify that

IF THE RESISTANCE IS HELD CONSTANT, INCREASING THEVOLTAGE WILL INCREASE THE CURRENT.

1. Connect the circuit in Figure 1 using a 4.7 k resistor.2. Set the voltage source to 2.0 V.

3. Measure the current through the resistor. Record this value in the following table.4. Repeat this procedure from 2.0V to 30.0V. And note down the required values in

the table (on next page).

Draw the following graphs on next pages.1. Draw relation between V & I on graph paper.2. Draw relation between P & V on graph paper.3. Draw relation between P & I on graph paper.

1RV

1RI

1RP

1R

0V 4.7k2V4V6V8V

10V12V14V16V18V20V22V24V25V26V28V30V


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Information:

The three forms of Ohms Law are:

=== I

VRandIRV

R

VI ,

The procedures in this experiment the student verified these formulas by comparingmeasured data with calculated data. Allow for a reasonable tolerance in your data. Forexample: Measured voltage = 15 V; calculated voltage = 14.8 V. To compare these, weuse[(measured - calculated)/calculated]*100%:

%4.1%1008.14

8.1415 +=

=

V

VVerrorpercentage


Signature: ___________________________

Checked by: ____________________________

Marks Awarded: __________________________


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Comments:______________________________________________________________

_______________________________________________________________________

____________________________________________________________________

Objectives

1. To understand the magnetic field strength around a coil.2. To study the factors for producing a magnetic field.

Discussion

In 1918, Hans Christan Oersted discovered that a current produced a

Magnetic field when he noticed how a wire carrying a current affected a compass.

If number of wire loops are wound in the same direction to form a coil,

More fields will add to make the flux lines through the coil even more dense.

The magnetic field through the coil becomes even stronger. The

More loops there are, the stronger the magnetic field becomes.

A helically wound coil that is made to produce a very strong magnetic field

is called a solenoid. The flux lines in a solenoid act the same as in a magnet.

The leave the N pole and go around the S pole. When a solenoid attracts

an iron bar, it will draw the bar inside the soil as shown in fig 11.1.

Lab # 5 Magnetic field strength


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Record the current value indicated by the ammeter.

I=_______________A

Turn off the power and turn the voltage control to the left completely.

Turn on the power

Slowly raise the positive power until the iron bar is drawn into the coil.

Record the values of the power voltage and the current.

E=__________________V

I=___________________A

Results

The results are only for your reference

Setup 3: 0.12A

Setup 4: 14.5V ; 0.12 A

Conclusion

In procedure steps 3 and 4, you have verified that the magnetic field built

Up by a coil is in proportion to the current flowing in the coil and the

Number of turns in the coil.


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The magnetic field of a coil be made stronger still by keeping an iron core

Inside the coil of wire. Since the soft iron is magnetic and has a low

reluctance, it allows more flux lines to be concentrated in it than would air.


Signature: ___________________________

Checked by: ____________________________

Marks Awarded: __________________________

Comments:______________________________________________________________

_____________________________________________________________________________________________________________________________________________

Objectives

1. To understand the self induction of a coil.2. To verify the phenomenon of self-induction.

DiscussionAny change in current causes an expansion or collapsing of the magnetic field around aconductor, which in turn induces an emf in the conductor. This is called self-induction.

The magnetic of the self-induced emf is proportion to the amplitude and frequency of thecurrent. By Lenzs law, we can also find the relation between the induced emf and theapplied voltage that causes the current flow is such that the current flow is such that thetwo voltages are always 1800 out of phase.

Since the magnitude of the magnetic flux is proportional to the magnitude of current inthe coil. The self-induced emf of a N-turns coil can be expressed by the equation e=-N/t. of course, the magnetic field of a coil can be made stronger, more flux line too, bykeeping a soft iron core inside the coil.

The circuit of fig.1.1 can be used to demonstrate the phenomenon of self-induction.When the switch is closed, the coil then build up a magnetic field (flux).if the switch is

Lab # 6 Self Induction


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opened, and then magnetic flux will collapse rapidly. Therefore, a large induced emf isproduced by a large amount of/tbrightness of the lamp will be maximum.

Procedure

1. Set the module IT-1005 on the main unit and locate the self induction block.2. According the fig.1.1 and 1.2, complete the experiment circuit with short-circuit

clips.3. Apply +5V to V+.4. Observe the states of the lamp while switch open or close write down your

comment.______________________________________________________________________________________________________________________________________________________________________________________________________

ResultsStep 4: the lamp has a maximum brightness when the switch is turned off.

Conclusion

Wherever there is magnetic flux, there is inductance. The inductance may be that of awire or a coil, but always magnetic flux and inductance go to gather. The self-inductance


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L of an N-turns coil can be express by the equation L=N /t. the unit of self-inductance L is the henrys (H).


Signature: ___________________________

Checked by: ____________________________

Marks Awarded: __________________________

Comments:______________________________________________________________

______________________________________________________________________

Objectives

1. To understand the mutual-induction between coils.2. To verify the phenomenon of mutual-induction.

Discussion

When the current in a coil is changing that a voltage will be induced in another coil. thiseffect is called mutual-induction.Consider fig.2.1 (a).At the instant when the switch S closes, then currentflowing throughthe coil 1 builds up a magnetic field (flux) around itself. A part of this flux which linksonly the coil 1. Then other part links both the 1 and 2 coils and therefore is a componentof mutual flux. This mutual flux produces a current flowing through the ammeter.

Lab # 7 Mutual Induction


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Similarly, a reverse current will flow the ammeter at the instant when the switch S opensas shown in fig.8.1 (b)

As mentioned before, wherever there is magnetic flux, there is inductance. the mutualflux is built up by a mutual inductance M. the mutual inductance M between two coilsdepends on their configuration, permeability ,and the individual inductance of each coil.

Procedure

1. Set the module IT-1005 on the main unit and locate the Mutual induction block.2. Complete the experiment circuit as shown in fig.8.2.


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3. Apply +5V to V+.4. On (Close) the SW and observe the indication on the A meter.

Does any current indication present on the A meter.Yes/No

5. Releases the SQ and observe the indication on the A meter?

Does any current indication present on the A meter? Yes /No6. Reduce the power supply and repeat steps 4 and 5.Record the results below.

Results and Conclusion

You have completed the experiment and should have found that the induced current

flows through the ammeter at the instant when the switch closes and then opens. thendecrease in applied voltage will cause the decrease in induced current.


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Signature: ___________________________

Checked by: ____________________________

Marks Awarded: __________________________

Comments:_____________________________________________________________________________________________________________________________________

_______________________________________________________________________

Objectives

1. To become familiar with Lenzs Law in electromagnetic induction.2. To become familiar with Faradays Law in electromagnetic induction.

Discussion

Lab # 8 Lenzs Law and Faradays Law


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Lenzs law states that a change in current or flux produces an emf whose direction is suchthat it opposes the change in current or flux. in other words when current or flux isdecreasing, the induced emf is in the same direction as current or flux and tries to Keepthe current or flux from decreasing and when a current or flux in increasing, the polarityof the induced emf is opposite to the direction of the current or flux and tries to prevent

Current or flux from increasing.

e can demonstrate these phenomena by considering the relative motion

Between movable magnet and a stationary coil as shown in Fig. when the magnet is putin the coil, the coil produces a magnetic field with the same pole as the end pole ofmagnet on the left and try prevent the magnet in and the induced current causes the

Pointer of ammeter to deflect to one side. lf the magnet is putting out the

Oil the coil will produce a magnetic field with the opposite pole to the pole

Of magnet on the left end trying to prevent the magnet out and the induced

Current causes the pointer of ammeter to deflect to the other side

illustrated in (b) and (d).

Procedure

1. Set the module IT-1006 on the main unit and locate the Lenzs Law

block.

2. According to Fig. 4.2 and 4.3, complete the experiment circuit.

3. Move up and down the magnet in the coil and observe the current

indication on the A meter.

Does any current indication present on the A meter?

Yes No

4.Change the moving speed of the magnet and _observe the current indication on the Ameter.

What is the relationship between the induced current and the moving speed?

5. Stay the magnet in the coil statically.

Does the current indication return to zero? Yes No


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Signature: ___________________________

Checked by: ____________________________

Marks Awarded: __________________________

Comments:_____________________________________________________________________________________________________________________________________

___________________________________________________________________

Objectives1 To learn the operating of magnetic-flux-density sensor.

Lab # 9 Magnetic Flux Detection


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2 To understand the application of the magnetic flux detector circuit.

Discussion

The most usually used magnetic-flux-density sensors are those using Hall-effect devices.

These devices produce an output voltage proportional to the flux density of a transversemagnetic field when a constant excitation current is passed through them. The polarity ofits output voltage is determined by the direction of the magnetic field. The hall-effectdevices commonly used in electronic circuits are semiconductor devices.

A circuit contracted to detect the magnetic flux is shown in fig.3.1.the magnetic-flux-density transducer U1 produces a dc output voltage when detecting a magnetic field. Themagnitude of output voltage is proportional to the flux density and the output voltage isamplified by the amplifiers U2-a and U2-b.the output voltage of U2-a produces a drivingcurrent through the LED1 or LED2.the positive output turns on the LED2 and thenegative turns on the LED1.the brightness of LEDs is proportional to the magnitude ofU2-b output voltage. The VR1 in the circuits is used for offset adjustment of U2-b outputvoltage. The VR1 in the circuit is used for offset adjustment to set a zero of outputvoltage when the circuit is initialized.

Procedure

1 Set the module It-1005 on the main unit and locate the magnetic flux Detectionblock.

2 Apply +12V and -12V the experiment circuit as shown in fig.3.1.


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3 Adjust VR1 to obtain a 0V at the output of U2-a(U2 PIN 7).4 Approach the magnet to U1 and observe the output voltage o f U2-b on the

voltmeter.5 What is change in the output voltage of U2-b as the magnetic field changes its

magnitude and polarity?

6 Observe the states of LED1 and LED2 and record the results below.

Results and Conclusion

The output voltage level of U2-b is reversely proportional to the distance from the sensorU1.When the N pole approaches to the U1, the output of from the sensor U1.When the Npole approached to the U1,the output of U2-b is a positive level and turns onLED2.Reversely,the output is negative and turns on LED1 when the S pole approaches tothe U1,the brightness of LEDs is Proportional to the voltage level at U2-b outputterminal.


Signature: ___________________________

Checked by: ____________________________

Marks Awarded: __________________________

Comments:_____________________________________________________________________________________________________________________________________

_______________________________________________________________________

__

Objective

Lab # 10 Introduction to Oscilloscope


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1. Measurement of Voltage and Frequency on Oscilloscope.

Equipment Required

1. Oscilloscope (Kenwood C4135A)

Theory of Oscilloscope:

Front Panel

1. Cathode Ray Tube (CRT)The effective display screen surface runs over an area of eight 1cm divisions alongthe vertical axis and ten 1cm divisions along the horizontal axis. With an innergratitude etched right into the tube face, the chance of measurement errors due toparallax occurring between the trace and the gratitude has been significantly reduced.There is also a % display for measuring rise time on the left edge of the gratitude.

2. Power Switch

A push-button type switch that turns the power source on and off. Pressing the leftedge of the gratitude.

3. Pilot Lamp

Light ups when the power is turned on.

4. CAL Terminal

A voltage terminal for calibration. To be used for adjusting the probe. Capable of 1volt peak to peak, positive, polarity, square wave signals with approx.1kHz is enable.

5. INTIN Control

For adjusting the brightness of the trace line.

6. FOCUS Control

For adjusting the focus and attaining the clearest display possible.

7. TRACE ROTA ControlFor adjusting the slope of the horizontal trace line. The slope of the line will changedue to such influences as the earths magnetic force. Use a screwdriver to keep thetrace line parallel with the horizontal axis gratitude.

8. ILLUM Control (CS4135A Only)

For adjustment the brightness of gratitude on the CRT.

9. GND Terminal

This is the ground terminal to be used when setting up a common ground with otherequipment.

10. POSITION Control

For adjusting the vertical position of the CHI & CH2 waveforms on the CRT screen.During X-Y operation it is used to adjust the position of Y-axis.

11. VOLTS/DIV Control

For setting the vertical axis sensitivity with the CHI & CH2 vertical axis attenuator. Itcan be set in steps of 1, 2 and 5. Setting the VARIABLE control all the way to theright at CAL enables calibrated vertical sensitivity. During X-Y operation, it becomesthe attenuator control for the Y axis.


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12. VERIABLE Control

For fine adjustment of CHI & CH2 vertical axis sensitivity. Allows continuousvariable adjustment within the VOLTS/DIV range. When set to the right at CAL, theattenuator can be calibrated. During X-Y operation, it becomes the fine adjustmentcontrol for the X-axis and y-axis.

13. AC-GND-DC SwitchFor selecting the CHI vertical axis input signal coupling mode.AC The input signal will be capacitively coupled. And all DC components will be

eliminated. The low range -3dB attenuation point will be 10 Hz or less whenusing either a 1:1 probe or a coaxial cable, and 1Hz or less when using acorrected 10:1 probe.

GND Vertical amplifier input is grounded, and the ground potential can be checked.At an input resistance of 1M ohm relative to the ground, the input signal is notGrounded. In this mode, the antitrace line jump circuit prevents the traceposition From changing suddenly when switching from GND to AC.

DC Provides direct coupling of the input signal, and measurement can be carried

out with the direct current component intact.14. INPUT Jacks

The CHI & CH2vertical axis input jack. During X-Y operation, CH1 becomes the Y-axis input jack and CH2 becomes the X-axis input jack.

15. BAL Control

For adjusting The DC balance of the CHI & CH2. The factory delivered the properadjustment. If discrepancy occurs due to circumferential temperature, Please use ascrew driver to keep the trace line not to move up and down when rotating theVOLT/DIV control.

16. VERT MODE Switch

For selecting the vertical axis operation mode.CH1 : For displaying the CH1 input signal on the CRT screen.CH2 : For displaying the CH2 input signal on the CRT screen.ALT : Switches between CHI & CH2 input signal for each sweep and

displays them on the CRT screenCHOP : For displaying CH1 & CH2 input signal one after the other on the CRT

screen, regardless of sweep and at an occurrence rate of about 250 kHz.ADD :For displaying combine waveform of CH1 & CH2 input signal on the

CRT screen However, when CH2 is set at ENVERT, the differencebetween CH1 & CH2 will be displayed.

17. CH2 INVERT Switch

When the button is pushed all the way in, the polarity of the CH2 input signal displaywill be inverted.

18. X-Y Oscilloscope Setting Switch


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When button is pushed all the way in, ignores the VERT MODE setting andcommences operation as an X-Y oscilloscope with CH1 as Y-axis and CH2 as X-axis.

19. MODE Selector Switch

For selecting trigger operation modes.AUTO : Sweep is performed by a trigger signal.

However, in the absence of a trigger signal, free run will commence and atrace will appear.

NORM : Sweep is performed by a trigger signal. In the absence of a suitabletrigger

Signal, a trace will not appear.FIX : Sweep trigger level is fixed. In this case, trigging is made regardless of

TRIGGER LEVEL control (28) setting.TV-F : Composite video signal verticalsync pulses are selected out and coupled

To the trigger circuit.TV-L : Composite video signal horizontal sync pulses are selected out and

Coupled to the trigger circuit.

Note : The trigger signal is capacitively coupled to the trigger circuit in thisoscilloscope. The trigger signal source will be selected by the VERTMODE setting.

VERT MODE TRIGING SIGNAL

CH1 CH1

CH2 CH2

ALTSwitches between CH1 and CH2 input signals for each sweep andselected for trigger signal source.

CHOP CHI

ADD Combine signal of CH1 and CH2 input signal.

Table-1 setting to the trigger signal source by the VERT MODE.

CH1 : The CH1 input signal will become the trigger signal source.CH2 : The CH2 input signal will become the trigger signal source.LINE : The commercial-use power source voltage waveform will become thetrigger

Signal source.EXT : The signal being input into the EXT TRIG jack will the trigger signalsource.

20. SLOPE ControlFor selecting the slope polarity of the trigger sweep signal. When the pushbutton isout, triggering will be performed with the trigger source signal rising. When the push-button is pressed in , triggering will be performed with the trigger source signalfalling.

21. Trigger Level Control.

For adjusting the trigger threshold level. This will determine at what point on thesignal waveform slope sweep will commence.


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22. External Trigger Input Jack

The input terminal for externally generated trigger signals. When the become theSOURCE switch is set at EXT; signals input through this terminal will become thetrigger signal source.

23. Horizontal Position Control

For adjusting the horizontal position of waveform displayed on the CRT screen.24. SWEEP TIME/DIV Control

For setting the sweep time. Setting can be carried out over 20 steps between 0.2s/div in 1-2-5 step sequence. When the VARIABLE control is set all the way to thefright at CAL, sweep rate values will become calibrated.

25. VARIABLE Control

Continuous sweep time adjustment can be carried out within the SWEEP TIME/DIVrange by this fine control. The sweep time becomes compensated by turning the CALall the way clock wise.

26. X10MAG Switch

Press this switch to magnify the display 10 X left and right from the center of CRTscreen.

The Display

Take a look at the oscilloscope display. Notice the grid markings on the screen - thesemarkings creates the graticule. Each vertical and horizontal line constitutes a majordivision. The graticule is usually laid out in an 8-by-10 division pattern. Labeling on theoscilloscope controls (such as volts/div and sec/div) always refers to major divisions. Thetick marks on the center horizontal and vertical graticule lines (see Figure 1) are calledminor divisions.

Many oscilloscopes display on the screen how many volts each vertical divisionrepresents and how many seconds each horizontal division represents. Manyoscilloscopes also have 0%, 10%, 90%, and 100% markings on the block (see Figure 1)to help make rise time measurements.


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Figure 1: An Oscilloscope graticule

Voltage Measurements

Voltage is the amount of electric potential, expressed in volts, between two points in acircuit. Usually one of these points is ground (zero volts) but not always. Voltages can

also be measured from peak-to-peak - from the maximum point of a signal to itsminimum point. You must be careful to specify which voltage you mean.

The oscilloscope is primarily a voltage-measuring device. Once you have measured thevoltage, other quantities are just a calculation away. For example, Ohm's law states thatvoltage between two points in a circuit equals the current times the resistance. From anytwo of these quantities you can calculate the third. Another handy formula is the powerlaw: the power of a DC signal equals the voltage times the current. Calculations are morecomplicated for AC signals, but the point here is that measuring the voltage is the firststep towards calculating other quantities.

Figure 2 shows the voltage of one peak - V[p] - and the peak-to-peak voltage - V[p-p] -,which is usually twice V[p]. Use the RMS (root-mean-square) voltage - V[RMS] - tocalculate the power of an AC signal.

Figure 2: Voltage Peak and Peak-to-peak Voltage

You take voltage measurements by counting the number of divisions a waveform spanson the oscilloscope's vertical scale. Adjusting the signal to cover most of the screen


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vertically, then taking the measurement along the center vertical graticule line having thesmaller divisions, makes for the best voltage measurements. The more screen area youuse, the more accurately you can read from the screen.

Figure 3: Measure Voltage on the Center Vertical Graticule Line

Many oscilloscopes have on-screen cursors that let you take waveform measurementsautomatically on-screen, without having to count graticule marks. Basically, cursors aretwo horizontal lines for voltage measurements and two vertical lines for timemeasurements that you can move around the screen. Readout shows the voltage or time attheir positions.

Time and Frequency Measurements

You take time measurements using the horizontal scale of the oscilloscope. Timemeasurements include measuring the period, pulse width, and timing of pulses.Frequency is the reciprocal of the period, so once you know the period, the frequency isone divided by the period. Like voltage measurements, time measurements are more

accurate when you adjust the portion of the signal to be measured to cover a large area ofthe screen. Taking time measurement along the center horizontal graticule line, havingsmaller divisions, makes for the best time measurements. (See Figure 4.)

Figure 4: Measure Time on the Center Horizontal Graticule Line


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Pulse and Rise Time Measurements

In many applications, the details of a pulse's shape are important. Pulses can becomedistorted and cause a digital circuit to malfunction, and the timing of pulses in a pulsetrain is often significant.

Standard pulse measurements arepulse width andpulse rise time. Rise time is the amountof time a pulse takes to go from the low to high voltage. By convention, the rise time ismeasured from 10% to 90% of the full voltage of the pulse. This eliminates anyirregularities at the pulse's transition corners. This also explains why most oscilloscopeshave 10% and 90% markings on their screen. Pulse width is the amount of time the pulsetakes to go from low to high and back to low again. By convention, the pulse width ismeasured at 50% of full voltage. See Figure 5 for these measurement points.

Figure 5: Rise Time and Pulse Width Measurement Points

Pulse measurements often require fine-tuning the triggering. To become an expert atcapturing pulses, you should learn how to use trigger hold off and how to set the digitaloscilloscope to capture pre-trigger data, as described earlier in the controls section.Horizontal magnification is another useful feature for measuring pulses, since it allowsyou to see fine details of a fast pulse.
https://www.cs.tcd.ie/courses/baict/bac/jf/labs/scope/controls.htmlhttps://www.cs.tcd.ie/courses/baict/bac/jf/labs/scope/controls.html


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Signature: ___________________________

Checked by: ____________________________

Marks Awarded: __________________________

Comments:____________________________________________________________________________________________________________________________________

_____________________________________________________________________

Objective

Find the frequency by using oscilloscope ina) Sinusoidal waveb) Square wave

c) Triangle wave

Lab # 11- To determine Frequency of AC signals


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Time and Frequency Measurements

You take time measurements using the horizontal scale of the oscilloscope. Time

measurements include measuring the period, pulse width, and timing of pulses.Frequency is the reciprocal of the period, so once you know the period, the frequency isone divided by the period.

T= 1/f


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Signature: ___________________________

Checked by: ____________________________Marks Awarded: __________________________

Comments:____________________________________________________________________________________________________________________________________

_____________________________________________________________________

Magnetic Circuit Nomenclature

Symbol Represents UnitsH Magnetic field strength Amp per metre (A/m)

B Magnetic flux density Tesla (T)

0 Permeability of free space Henries per meter (H/m)

r Relative permeability n/a

L Self-inductance Henries (H)

Lab # 12- To draw B-H curve


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M Mutual inductance Henries (H)

Magnetic flux Weber (Wb)

B-H Curve of Vacuum

The magnetic flux density in vacuumIs directly proportional to theMagnetic field intensity:

B = oHWhere

o = permeability constant= 4 x 10-7 H/m

Non-magnetic materials such asCopper, paper, rubber and airHave B-H curves almost identical


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To that of vacuum. TheseMaterials never saturate!

B-H Curve of Magnetic Materials

The magnetic flux density in magnetic materials also depends upon themagnetic field intensity:B = r o HWhere

r = relative permeability of magnetic materialHowever, relative permeability is not constantand varies with the flux

density in the material. Consequently, the B-H relationship formagnetic materials is non-linear

B-H Curve of Magnetic Materials


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Magnetic Materials

Commonly used magnetic materials:

Permanent magnets


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Rare-earth magnets (highest flux/field and high cost) Ferrite magnets (low-medium flux/field and low cost)

Laminated materials

Iron-silicon alloys High relative permeability but low conductivity Used to minimize eddy currents at power frequencies (Hz)


Signature: ___________________________

Checked by: ____________________________

Marks Awarded: __________________________

Comments:______________________________________________________________

___________________________________________________________________________________________________________________________________________

ObjectiveTo study the I-V characteristics of a p-n junction diode both ina) Forward Biasb) Reverse Bias

Lab # 13-To study the Characteristics of P-N junctions


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ApparatusPower Supply (0-30V), Voltmeter (0-30V), Ammeter (A & mA range), resistors, andP-n junction diode

Forward Biased diode Reverse Biased diode

Procedure:1. Wire up the circuit shown in figure.2. Record the voltage across the diode (V) and current (I) through it as a function of

input voltage.3. Repeat the experiment of the reverse biased diode.4. Plot the relevant graphs.5. Find the equation of dc load line and plot it along with I-V characteristics of fig.

Reverse Biased Junction Diode

When a diode is connected in a Reverse Bias condition, a positive voltage is applied tothe N-type material and a negative voltage is applied to the P-type material. The positivevoltage applied to the N-type material attracts electrons towards the positive electrodeand away from the junction, while the holes in the P-type end are also attracted awayfrom the junction towards the negative electrode.

The net result is that the depletion layer grows wider due to a lack of electrons and holesand presents a high impedance path, almost an insulator. The result is that a highpotential barrier is created thus preventing current from flowing through thesemiconductor material.

Reverse Biased Junction Diode showing an Increase in the Depletion Layer


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This condition represents a high resistance value to the PN junction and practically zero

current flows through the junction diode with an increase in bias voltage. However, avery small leakage current does flow through the junction which can be measured inmicroamperes, (A). One final point, if the reverse bias voltage Vr applied to the diode isincreased to a sufficiently high enough value, it will cause the PN junction to overheatand fail due to the avalanche effect around the junction. This may cause the diode tobecome shorted and will result in the flow of maximum circuit current, and this shown asa step downward slope in the reverse static characteristics curve below.

Reverse Characteristics Curve for a Junction Diode


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Sometimes this avalanche effect has practical applications in voltage stabilizing circuitswhere a series limiting resistor is used with the diode to limit this reverse breakdowncurrent to a preset maximum value thereby producing a fixed voltage output across thediode. These types of diodes are commonly known asZener Diodes and are discussed ina later tutorial.

Forward Biased Junction Diode

When a diode is connected in a Forward Bias condition, a negative voltage is applied tothe N-type material and a positive voltage is applied to the P-type material. If thisexternal voltage becomes greater than the value of the potential barrier, approx. 0.7 voltsfor silicon and 0.3 volts for germanium, the potential barriers opposition will beovercome and current will start to flow.

This is because the negative voltage pushes or repels electrons towards the junctiongiving them the energy to cross over and combine with the holes being pushed in the

opposite direction towards the junction by the positive voltage. This results in acharacteristics curve of zero current flowing up to this voltage point, called the "knee" onthe static curves and then a high current flow through the diode with little increase in theexternal voltage as shown below.

Forward Characteristics Curve for a Junction Diode
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The application of a forward biasing voltage on the junction diode results in the depletionlayer becoming very thin and narrow which represents a low impedance path through thejunction thereby allowing high currents to flow. The point at which this sudden increasein current takes place is represented on the static I-V characteristics curve above as the"knee" point

Forward Biased Junction Diode showing a Reduction in the Depletion Layer

This condition represents the low resistance path through the PN junction allowing verylarge currents to flow through the diode with only a small increase in bias voltage. Theactual potential difference across the junction or diode is kept constant by the action ofthe depletion layer at approximately 0.3v for germanium and approximately 0.7v for

silicon junction diodes.

Since the diode can conduct "infinite" current above this knee point as it effectivelybecomes a short circuit, therefore resistors are used in series with the diode to limit itscurrent flow. Exceeding its maximum forward current specification causes the device todissipate more power in the form of heat than it was designed for resulting in a veryquick failure of the device.


Signature: ___________________________Checked by: ____________________________

Marks Awarded: __________________________

Comments:____________________________________________________________________________________________________________________________________________________________________________________________________________


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ObjectiveTo plot the V-I characteristics of Zener diode in

a) Forward biasedb) Reverse biased

Apparatus

Zener diode, resistor, power supply, voltmeter, Ammeter,

TheoryA p-n junction does not conduct when reverse biased but if reverse voltage is increased,at particular voltage it start conducting heavily. This voltage is called breakdown

voltage. High current through diode can permanently damage it. But Zener diode inreverse bias maintain almost constant voltage in reverse biased across it terminals.Whatever may be input voltage and current through it. So Zener diode is p-n junctiondiode specially made to work in reverse region.

Procedure1. Wire up the circuit shown in figure2. Record the voltage across the diode (V) and current (I) through it as a function of

input voltage. Find Zenar Voltage3. Connect the circuit shown in figure 2.2. Keep the load resistance RL at 3.3 k.

Vary the input voltage in short steps and record the voltage across the zener andcurrent flowing through the zener. Repeat the above step for various RL values.

4. Plot the relevant graphs.

Lab # 14-To study the Characteristics of Zener diode


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Result

The breakdown voltage observer in reverse bias is that for the given zener diode. Itprovide constant voltage by into the breakdown region.


Signature: ___________________________

Checked by: ____________________________

Marks Awarded: __________________________


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Comments:_____________________________________________________________________________________________________________________________________

_______________________________________________________________________

Apparatus: LEDs, Bread Board , Resistors , Power Supply , DMM

Light-emitting diode

Red, green and blue LEDs of the 5mm type

Electronic symbol

A light-emitting diode (LED) is an electronic light source. The first LED was built inthe 1920s byOleg Vladimirovich Losev, a radio technician who noticed that diodes usedin radio receivers emitted lightwhen currentwas passed through them. The LED wasintroduced as a practical electronic component in 1962.

All early devices emitted low-intensity red light, but modern LEDs are available acrossthe visible, ultraviolet and infra redwavelengths, with very high brightness.

LEDs are based on the semiconductor diode. When the diode is forward biased (switchedon), electronsare able to recombine with holes and energy is released in the form of light.This effect is called electroluminescenceand the colorof the light is determined by theenergy gap of the semiconductor. The LED is usually small in area (less than 1 mm2)with integrated optical components to shape its radiation pattern and assist in reflection.

LEDs present many advantages over traditional light sources including lowerenergyconsumption, longerlifetime, improved robustness, smaller size and faster switching.However, they are relatively expensive and require more precisecurrent and heatmanagementthan traditional light sources.

Lab # 15-To study the Characteristics and Operation of LED
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Applications of LEDs are diverse. They are used as low-energy indicators but also forreplacements for traditional light sources in general lighting and automotive lighting. Thecompact size of LEDs has allowed new text and video displays and sensors to bedeveloped, while their high switching rates are useful in communications technology.

Practical use

The first commercial LEDs were commonly used as replacements forincandescentindicators, and in seven-segment displays, first in expensive equipment such aslaboratory and electronics test equipment, then later in such appliances as TVs, radios,telephones, calculators, and even watches (see list ofsignal applications). These redLEDs were bright enough only for use as indicators, as the light output was not enough toilluminate an area. Later, other colors became widely available and also appeared inappliances and equipment. As the LED materials technology became more advanced, thelight output was increased, while maintaining the efficiency and the reliability to anacceptable level. The invention and development of the high power white light LED ledto use for illumination (see list ofillumination applications). Most LEDs were made inthe very common 5 mm T1 and 3 mm T1 packages, but with increasing power output, it

has become increasingly necessary to shed excess heat in order to maintain reliability, somore complex packages have been adapted for efficient heat dissipation. Packages forstate-of-the-art high power LEDs bear little resemblance to early LEDs.
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Technology

Parts of an LED

The inner workings of an LED
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http://en.wikipedia.org/wiki/File:Diode-IV-Curve.svg


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Signature: ___________________________

Checked by: ____________________________

Marks Awarded: __________________________

Comments:____________________________________________________________________________________________________________________________________

Apparatus: Varactor Diode, Tunnel Diode

Tunnel diode schematic symbol

These diodes have a heavily dopedpn junction only some 10 nm (100 ) wide. Theheavy doping results in a brokenbandgap, where conduction bandelectron stateson then-side are more or less aligned with valence bandhole states on the p-side.

Tunnel diodes were manufactured bySONYfor the first time in 1957[1] followed byGeneral Electricand other companies from about 1960, and are still made in low volumetoday.[2] Tunnel diodes are usually made from germanium, but can also be made in

Lab # 16 To study the Characteristics of Varactor and Tunnel Diode.
http://en.wikipedia.org/wiki/Doping_(semiconductor)http://en.wikipedia.org/wiki/P%E2%80%93n_junctionhttp://en.wikipedia.org/wiki/P%E2%80%93n_junctionhttp://en.wikipedia.org/wiki/%C3%85ngstr%C3%B6mhttp://en.wikipedia.org/wiki/Bandgaphttp://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Electron_configurationhttp://en.wikipedia.org/wiki/Electron_configurationhttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/SONYhttp://en.wikipedia.org/wiki/SONYhttp://en.wikipedia.org/wiki/SONYhttp://en.wikipedia.org/wiki/Tunnel_diode#cite_note-0http://en.wikipedia.org/wiki/General_Electrichttp://en.wikipedia.org/wiki/General_Electrichttp://en.wikipedia.org/wiki/Tunnel_diode#cite_note-1http://en.wikipedia.org/wiki/Germaniumhttp://en.wikipedia.org/wiki/File:GE_1N3716_tunnel_diode.jpghttp://en.wikipedia.org/wiki/File:GE_1N3716_tunnel_diode.jpghttp://en.wikipedia.org/wiki/File:Tunnel_diode_symbol.svghttp://en.wikipedia.org/wiki/File:Tunnel_diode_symbol.svghttp://en.wikipedia.org/wiki/Doping_(semiconductor)http://en.wikipedia.org/wiki/P%E2%80%93n_junctionhttp://en.wikipedia.org/wiki/%C3%85ngstr%C3%B6mhttp://en.wikipedia.org/wiki/Bandgaphttp://en.wikipedia.org/wiki/Conduction_bandhttp://en.wikipedia.org/wiki/Electron_configurationhttp://en.wikipedia.org/wiki/Valence_bandhttp://en.wikipedia.org/wiki/Electron_holehttp://en.wikipedia.org/wiki/SONYhttp://en.wikipedia.org/wiki/Tunnel_diode#cite_note-0http://en.wikipedia.org/wiki/General_Electrichttp://en.wikipedia.org/wiki/Tunnel_diode#cite_note-1http://en.wikipedia.org/wiki/Germanium


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gallium arsenide and silicon materials. They can be used asoscillators, amplifiers,frequency converters and detectors.[3]:735

Forward bias operation

Under normal forward biasoperation, as voltage begins to increase, electronsat firsttunnel through the very narrow pn junction barrier because filled electron states in theconduction band on the n-side become aligned with empty valence band hole states onthe p-side of the pn junction. As voltage increases further these states become moremisaligned and the current drops this is called negative resistancebecause currentdecreases with increasing voltage. As voltage increases yet further, the diode begins tooperate as a normal diode, where electrons travel by conduction across the pn junction,and no longer by tunneling through the pn junction barrier. Thus the most importantoperating region for a tunnel diode is the negative resistance region.

Reverse bias operation

When used in the reverse direction they are called back diodes and can act as fastrectifiers with zero offset voltage and extreme linearity for power signals (they have anaccurate square law characteristic in the reverse direction).

Underreverse bias filled states on the p-side become increasingly aligned with emptystates on the n-side and electrons now tunnel through the pn junction barrier in reversedirection this is the Zener effect that also occurs in zener diodes.

Technical comparisons
http://en.wikipedia.org/wiki/Gallium_arsenidehttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Electronic_oscillatorhttp://en.wikipedia.org/wiki/Electronic_oscillatorhttp://en.wikipedia.org/wiki/Amplifierhttp://en.wikipedia.org/wiki/Frequency_converterhttp://en.wikipedia.org/wiki/Detector_(radio)http://en.wikipedia.org/wiki/Tunnel_diode#cite_note-Fink-2http://en.wikipedia.org/wiki/Tunnel_diode#cite_note-Fink-2http://en.wikipedia.org/wiki/Tunnel_diode#cite_note-Fink-2http://en.wikipedia.org/wiki/Voltage_biashttp://en.wikipedia.org/wiki/Voltage_biashttp://en.wikipedia.org/wiki/Electronshttp://en.wikipedia.org/wiki/Electronshttp://en.wikipedia.org/wiki/Negative_resistancehttp://en.wikipedia.org/wiki/Rectifiershttp://en.wikipedia.org/wiki/Reverse_biashttp://en.wikipedia.org/wiki/Zener_diodehttp://en.wikipedia.org/wiki/Zener_diodehttp://en.wikipedia.org/wiki/File:Negative_differential_resistance.pnghttp://en.wikipedia.org/wiki/File:Negative_differential_resistance.pnghttp://en.wikipedia.org/wiki/Gallium_arsenidehttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Electronic_oscillatorhttp://en.wikipedia.org/wiki/Amplifierhttp://en.wikipedia.org/wiki/Frequency_converterhttp://en.wikipedia.org/wiki/Detector_(radio)http://en.wikipedia.org/wiki/Tunnel_diode#cite_note-Fink-2http://en.wikipedia.org/wiki/Voltage_biashttp://en.wikipedia.org/wiki/Electronshttp://en.wikipedia.org/wiki/Negative_resistancehttp://en.wikipedia.org/wiki/Rectifiershttp://en.wikipedia.org/wiki/Reverse_biashttp://en.wikipedia.org/wiki/Zener_diode


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A rough approximation of the VI curve for a tunnel diode, showing the negativedifferential resistance region

In a conventional semiconductor diode, conduction takes place while the pn junction isforward biased and blocks current flow when the junction is reverse biased. This occurs

up to a point known as the reverse breakdown voltage when conduction begins (oftenaccompanied by destruction of the device). In the tunnel diode, the dopant concentrationin the p and n layers are increased to the point where the reverse breakdown voltagebecomes zero and the diode conducts in the reverse direction. However, when forward-biased, an odd effect occurs called quantum mechanical tunnelling which gives rise to aregion where an increase in forward voltage is accompanied by a decrease in forwardcurrent. This negative resistanceregion can be exploited in a solid state version of thedynatron oscillatorwhich normally uses a tetrodethermionic valve(or tube).

Varactor Diode

In electronics, a varicap diode, varactor diode, variable capacitance diode, variablereactance diode ortuning diode is a type ofdiodewhich has a variablecapacitance that

is a function of the voltage impressed on its terminals.

Applications

Varactors are principally used as a voltage-controlledcapacitor, rather than as rectifiers.They are commonly used inparametric amplifiers,parametric oscillators and voltage-controlled oscillators as part ofphase-locked loops and frequency synthesizers.

Operation
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Internal structure of a varicap

Operation of a varicap

Varactors are operatedreverse-biased so no current flows, but since the thickness of thedepletion zonevaries with the applied bias voltage, the capacitance of the diode can bemade to vary. Generally, the depletion region thickness is proportional to the square rootof the applied voltage; and capacitance is inversely proportional to the depletion regionthickness. Thus, the capacitance is inversely proportional to the square root of appliedvoltage.
http://en.wikipedia.org/wiki/Reverse-biasedhttp://en.wikipedia.org/wiki/Reverse-biasedhttp://en.wikipedia.org/wiki/Depletion_zonehttp://en.wikipedia.org/wiki/Depletion_zonehttp://en.wikipedia.org/wiki/Square_roothttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/File:Varactor_function.svghttp://en.wikipedia.org/wiki/File:Varactor_function.svghttp://en.wikipedia.org/wiki/File:Varactor.svghttp://en.wikipedia.org/wiki/File:Varactor.svghttp://en.wikipedia.org/wiki/Reverse-biasedhttp://en.wikipedia.org/wiki/Depletion_zonehttp://en.wikipedia.org/wiki/Square_roothttp://en.wikipedia.org/wiki/Capacitance


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