CAIE IGCSE Physics 4.3.3 Action and Use of Circuit Components Topic Practice

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Covered syllabus points

4.3.3.1—P.d. across an electrical conductor4.3.3.2—Action of a variable potential divider4.3.3.3—Potential divider relation: R1/R2 =

Question 1

[Maximum number: 3]

Fig. 8.1 shows a circuit. The circuit is designed to switch on a night light when the surroundings are dark.

Fig. 8.1

Fig. 8.1

The surroundings change from light to dark.
1. State the effect of this change on the resistance of the LDR.
2. State and explain the effect of this change on the p.d. across the light-emitting diode (LED).

Question 2

[Maximum number: 2]

Fig. 7.1 shows a circuit.

Fig. 7.1

Fig. 7.1

Calculate the value of Vout V_{\text {out }} when the value of R is 3.0kΩ3.0 \mathrm{k} \Omega.

Vout =V_{\text {out }}=

Question 3

[Maximum number: 5]

Fig. 7.1 shows a circuit that contains a battery, a switch, a voltmeter and three 40Ω40 \Omega resistors, R1\mathrm{R}_{1}, R2R_{2} and R3R_{3}.

Fig. 7.1

Fig. 7.1

The switch is open and resistors R1R_{1} and R2R_{2} form a potential divider.

Question (a)

(a)

Describe what is meant by a potential divider.

[ 2 ]

Question (b)

(b)

The reading on the voltmeter is 7.5 V .

[ 1 ]

Question (i)

(i)

Calculate the electromotive force (e.m.f.) of the battery.

e.m.f. =
[ 1 ]

Question (c)

(c)

Calculate the reading on the voltmeter when the switch is closed.
reading =

[ 2 ]
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