EMF and PD

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Notes: Physics: OCR A: Unit 2: Module 2: EMF and PD

(a) define potential difference (p.d.)

Potential difference (or voltage) between two point in a circuit is the energy transferred per unit charge moved between those points

(b) select and use the equation W = VQ

W is energy in joules. It is the work you do moving the charge

Q is the charge that is having work done on it

(c) define the volt

1 volt = 1 joule per coulomb ...... 1V = 1JC-1

The potential difference is 1 volt when you convert 1 joule of energy moving 1 coulomb of charge through the component

(d) describe how a voltmeter may be used to

determine the p.d. across a component

A voltmeter must be connected in parallel so that the resistance is infinite and no current can flow

(e) define electromotive force (e.m.f.) of a

source such as a cell or a power supply

Electromotive force is the electrical energy given to each coulomb of charge

(f) describe the difference between e.m.f. and p.d. in terms of energy transfer

PD is the energy transformed per unit charge from electrical energy to another form of energy such as light or heatEMF is the energy transformed per unit charge from potential energy to electrical energy