CAIE IGCSE Physics 4.2.3 Electromotive force & potential difference Question Bank

Practise linking e.m.f., p.d., work done and charge in circuits, using E = W/Q or V = W/Q with volts, joules and coulombs.

Exam points

calculate energy, charge, e.m.f. or p.d. from E = W/Q and V = W/Q
distinguish source e.m.f. from p.d. across a component in a circuit diagram
interpret volt as J/C and choose correct units in tabular circuit data

Covered syllabus points

4.2.3.1—Electromotive force (e.m.f.) as the 4.2.3.2—E.m.f. is measured in volts (V)4.2.3.3—Potential difference (p.d.) as the 4.2.3.4—P.d. between two points is measured in 4.2.3.5—Use of voltmeters (analogue and 4.2.3.6—E.m.f.: E = W/Q 4.2.3.7—P.d.: V = W/Q

[Maximum number: 2]

A washing machine has an electric motor and an electric heater. Fig. 7.1 shows a simplified circuit diagram for the washing machine.

Fig. 7.1

The heater has a resistance of $25 \Omega$ and the power supply has an electromotive force (e.m.f.) of 230 V .

State the meaning of electromotive force.

[Maximum number: 1]

Which unit is used to measure electromotive force (e.m.f.)?

ampere

joule

volt

watt

[Maximum number: 2]

A potential divider is made by connecting a light-dependent resistor (LDR) and a thermistor in series. Fig. 6.1 shows the potential divider, a voltmeter and a direct current (d.c.) power supply connected into a circuit.

Fig. 6.1

The voltmeter measures the potential difference (p.d.) across the LDR.

Define potential difference (p.d.).

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Covered syllabus points

4.2.3 Electromotive force and potential difference question 1

4.2.3 Electromotive force and potential difference question 2

4.2.3 Electromotive force and potential difference question 3