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CAIE IGCSE Physics 4.3.3 Action & use of circuit components Question Bank

Practise interpreting potential dividers, sensor components and p.d. changes using circuit diagrams, tables and calculations.

Syllabus
2026–2028
Course
Physics 0625

Exam points

  • explain LDR or thermistor resistance changes using voltage sharing in a potential divider
  • calculate Vout, e.m.f. or resistor values from p.d. ratios and series resistance
  • choose LDR, thermistor or fixed-resistor positions so output p.d. rises in the stated condition

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 =

4.3.3 Action and use of circuit components question 1

[Maximum number: 3]

Fig. 6.1 shows a circuit which includes an LDR (light-dependent resistor).

Fig. 6.1

Fig. 6.1

The LDR is in a brightly lit room. The voltmeter reads 1.8 V .

The light level in the room changes from bright to dark.

State and explain the effect on the voltmeter reading.
statement
explanation

4.3.3 Action and use of circuit components question 2

[Maximum number: 3]

Question (a)

(a)

Fig. 8.2 shows a circuit.

Fig. 8.2

Fig. 8.2

The three cells are identical and have zero resistance.
The resistors R1,R2R_{1}, R_{2} and R3R_{3} are identical.
The reading on the voltmeter is 6.0 V .
When the diode is conducting, it has zero resistance and zero potential difference (p.d.) across it.

[ 3 ]

Question (i)

(i)

Determine the ratio of the p.d. across R2R_{2} to the p.d. across R3R_{3}.

[ 1 ]

Question (ii)

(ii)

All the cells are reversed.
1. State and explain the change in current in R1R_{1}.
2. Determine the new value of the ratio of the p.d. across R2R_{2} to the p.d. across R3R_{3}.

[ 2 ]
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