Electricity 2Electricity 2

Voltage, Potential Voltage, Potential Difference and Difference and Electromotive ForceElectromotive Force

Aims of the Lesson- VoltageAims of the Lesson- Voltage

Recall the meanings of the phrases Recall the meanings of the phrases ‘‘potential differencepotential difference’’ and and ‘‘electromotive forceelectromotive force’’

Recall that in a series circuit the sum Recall that in a series circuit the sum of the voltages is equal to the of the voltages is equal to the voltage across the whole circuit.voltage across the whole circuit.

VoltageVoltage

Page 118Page 118

- Worksheet on Alexandro Volta (basic - Worksheet on Alexandro Volta (basic notes on voltage)notes on voltage)

Complete questions 9 and 10 pg 121Complete questions 9 and 10 pg 121

Total PD in a circuitTotal PD in a circuit

Read page 119 and 120Read page 119 and 120 Copy out the statement in the blue Copy out the statement in the blue

box.box. Complete the Worksheet Complete the Worksheet

‘Understanding Voltage’‘Understanding Voltage’

Energy Saver Light BulbEnergy Saver Light Bulb

- Transfers Transfers Electrical to Light and HeatElectrical to Light and Heat- 220 Joules of energy220 Joules of energy transferred for transferred for

every coulomb of charge passing every coulomb of charge passing throughthrough

- For a current of 140 mA (0.14 A)For a current of 140 mA (0.14 A)- 0.14 Coulombs passing through each 0.14 Coulombs passing through each

secondsecond

Energy = 220 / 0.14 = 1571 JEnergy = 220 / 0.14 = 1571 J

Aim of the LessonAim of the Lesson

Clearly define what is meant by the Clearly define what is meant by the current and voltage of a circuit!current and voltage of a circuit!

Recall why a voltmeter is placed into Recall why a voltmeter is placed into a circuit in parallel and an ammeter a circuit in parallel and an ammeter is placed into a circuit in seriesis placed into a circuit in series

Eh… explain that to me please!Eh… explain that to me please!

What does the What does the current flowing a current flowing a circuitcircuit mean? mean?

What does the What does the voltage of a voltage of a componentcomponent mean? mean?

Number of Coulombs

Going past a point every

second

Amount of Energy

transferredFor every Coulomb

That passes through a component

Voltmeter actionVoltmeter action

How does a voltmeter go into a How does a voltmeter go into a circuit?circuit?

First of all we need a circuit…

Equipment you need-

What is the Voltmeter measuring?

Energy in and energy out, for each coulomb passing through a component

Sorry Sir but I’m gonna’ have to Sorry Sir but I’m gonna’ have to search you…search you…

What have you got on you, Mr Coulomb?

Experiment- Investigating VoltageExperiment- Investigating Voltage

How does the voltage of a component in a series circuit compare to the voltage of a component in a parallel circuit?

The following two circuits are set up and the voltage is measured across both 1.5 V batteries and across each 1.5V bulb individually.

Experiment- Investigating VoltageExperiment- Investigating Voltage

VV11 = = VV22 = = VV33 = =

VV44 = = VV5 5 == VV66 = =

+

V1

Series+ Parallel

Series

Parallel

Investigating Voltage - ConclusionInvestigating Voltage - Conclusion

In a In a seriesseries circuit the voltage supplied circuit the voltage supplied by the battery is by the battery is divideddivided between the between the components.components.

In a In a parallelparallel circuit the voltage supplied circuit the voltage supplied is the is the samesame as the component’s voltage. as the component’s voltage.

The The energyenergy each coulomb each coulomb receivedreceived (from the battery) is (from the battery) is equalequal to the to the totaltotal energy energy given outgiven out as it goes round the as it goes round the circuit (conservation of energy).circuit (conservation of energy).

Voltage in a series circuitVoltage in a series circuit

V

V V

If the voltage across the battery is 6V…

…and these bulbs are all identical…

…what will the voltage across each bulb be? 2V

Voltage in a series circuitVoltage in a series circuit

V

V

If the voltage across the battery is 6V…

…what will the voltage across two bulbs be?

4V

Voltage in a parallel circuitVoltage in a parallel circuitIf the voltage across the batteries is 4V…

What is the voltage here?

And here?

V

V4V

4V

In a PARALLEL circuit:

Current SPLITS UP down each “strand”

Voltage is THE SAME across each”strand”

SummarySummaryIn a SERIES circuit:

Current is THE SAME at any point

Voltage SPLITS UP over each component

An example question:An example question:

V1

V2

6 V

3 A

A1

A2

V3

A3

What is the easiest path for the Coulombs of Charge?

All bulbs are identical in

power rating

Advantages of parallel circuits…Advantages of parallel circuits…

There are two main reasons why parallel circuits are used more commonly than series circuits:

1) Extra appliances (like bulbs) can be added without affecting the output of the others

2) If one appliance breaks it won’t affect the others either