ELECTRICITYELECTRICITY1)1)ELECTRICITY AND MATTER.ELECTRICITY AND MATTER.

1.1. Conductor and insulators1.2. How to obtain electricity1.3. The transport of electric energy1.4. Effects of electric current

2)2)Electric quantitiesElectric quantities 2,1. Electric current2.2. Voltage2.3. Resistance.

3)3) Ohm's lawOhm's law4)4)Electric circuits Electric circuits

4.1. Components of an electric circuit4.2. Representation and symbols.

5)5)Types of circuits. Types of circuits. 5.1. Series circuits5.2. Parallel circuits5.3. Series-parallel combination circuits

IES Río CabeCovadonga Yugueros

Valbuena

There are lots of different ways to connect components in a circuit

The most common connections:

5. Types of circuits5. Types of circuits

ParallelParallel circuitscircuitsSeries Series circuitscircuits

5,1. Series circuits5,1. Series circuits

Components are placed one after the other in the circuit. There is only one possible path for the electric current to flow through

+ -

Series Series circuitscircuits

The same currentcurrent flows through all the components

RR11

RR22

RR33 RRtotaltotal = = RR11 + + RR22 + + RR33

The voltage of the battery is the sum of the voltages of all the receptors in the circuit.:

V V totaltotal

B1B1 B2B2 B3B3

+

V1V1 V2V2 V3V3VVtotaltotal = = V V11 + + VV22 + + VV33

The total resistanceresistance is the sum of all the resistances

Series circuitsSeries circuits

If one of the components stops working, none of them will work because the circuit will be open.

Batteries en series:Batteries en series: If we connect some batteries in serie, the total voltage is the sum of the voltage in each battery

+9 V

+9 V

+9 V

Batteries in series: The negative pole of one battery with the positive pole of the next one.

+ +

1,5V 1,5V

3V3V

+ +

1,5V 1,5V

4,5V4,5V

+

1,5V

Series circuitsSeries circuits

Fuses and control elements are always connected in series with the receptors that must be protected or controlled.

+

-

Control element

Fuse

PracticePractice Series Series CircuitCircuit Practice2 Series Practice2 Series CircuitCircuit

In the following circuit calculate:

* The total resistance

* Total current

* Voltage on each receptor.

Example of a series circuit:Example of a series circuit:

R1

50 Ω 100 Ω

+

R2

30 Ω

9V

a RRtotaltotal = = RR11 + + RR22 + + RR33

VV11 = R = R11 * I * I

b IItotaltotal = V = VTotalTotal / /RRTotalTotal Ohm's lawOhm's law

In a series circuit the current is the same in all elements.

cOhm's law in each component

VV22 = R = R22 * I * I

5,2. 5,2. ParallelParallel circuitcircuit

The components are connected on different branches of the wire.There are several possible paths for the electric current to flow through

+

- +

Diagram

Parallel circuitParallel circuit

The intensityintensity is shared by all the possible paths

IItotaltotal = = II11 + + II22

The current will be higher

As lower be the resistanceresistance

10 Ω 5 Ω

IItotaltotal

II11

II22

II11

II22

IItotaltotal

+

Total current is the sum of the intensity in each branch

IItotaltotal = I = I11 + I + I22 + I + I33

Parallel circuitsParallel circuits

We can calculate the total resistanceresistance using this formula

Voltage is the same in each branch

VVtotaltotal = = VV11 = = VV22

+

Vtotal

Vtotal V

1 V2

11RRtotaltotal

= 11RR11

11RR22

+ 11RR33

+

R1

R2

100 Ω

100 Ω

9 V+

11

RRtottot =11RR11

11RR22 +

11RRtottot

= 11100100

+ 11100100

= 22100100

11RRtottot =

115050 RRtottot = 5050ΩΩ

Parallel circuitsParallel circuits

If one of the components in parallel stops working, the rest continue to work because the electric current takes another path.

Batteries en parallel:Batteries en parallel: Poles of the same sign are joined together. These batteries must have the same voltage, and the circuit is equivalent to having another battery of the same voltage but longer.

+

9 V

+

9 V

+9 V

1,5V

+

+

1,5V

+

1,5 V1,5 V

Parallel circuitsParallel circuits

If a wire is in parallel with a receptor, this will not work, because the current will choose the path that less work required.

This is a short circuitshort circuit

+

+

Lamp is in a short circuitLamp is in a short circuit

Practice 2 Practice 2 ParallelParallel Circuit Circuit

Practice 1 Practice 1 PParallel arallel CircuitCircuit

In the folllowing circuit claculate:

* Total resistance

* Total current

* Voltage and current in each component.

Example of a parallel circuit:Example of a parallel circuit:

a

II11 = V/R = V/R11

b IItotaltotal = V = VTotalTotal / /RRTotalTotal Ohm's lawOhm's law

In a parallel circuit the voltage is the same for all elements.

cOhm's law in each component

II22 = V/R = V/R22

+

M

12 Ω 6 Ω6V

11RRtotaltotal

= 11RR11

11RR22

+ 11RR33

+

5,3. Series-parallel combination circuits5,3. Series-parallel combination circuits

These circuits contain devices connected in series and in parallel

Diagram

+

-B3

B1 B2

+

B1

B2B3

Series-parallel combination circuits Series-parallel combination circuits

In the following circuit analyze what elements are in series and which are in parallel.

+

9 V

B1

B2 B3

B2 y B3 are in parallelB1 is in series with the parallel of B2 - B3

B1 y B2 are in series

Motor is in parallel with B1 - B2

+

MM

B1 B2