CAIE IGCSE Physics Resistance Question Bank
Practise calculating resistance, connecting meters, interpreting component I–V characteristics and comparing wires by length and cross-sectional area.
- Syllabus
- 2026–2028
- Course
- Physics 0625
Exam points
- use R = V/I with voltmeter and ammeter readings, including series or parallel circuit steps
- identify resistor, filament-lamp and diode behaviour from the shape and gradient of an I–V graph
- apply R proportional to length/area to compare wires and account for diameter-squared changes
Covered syllabus points
4.2.4 Resistance question 1
Fig. 7.1 shows three identical lamps and an ammeter connected to a power supply.
Fig. 7.1
The switches are closed. Each lamp is rated at 60 W and operates at its normal working voltage of 110 V .
Question (a)
(a)
Calculate the resistance of the filament of one of the lamps when working normally.
resistance =
[ 2 ]
Question (b)
(b)
Another lamp X has a filament with twice the resistance of each lamp in the circuit of Fig. 7.1. The material and the temperature of the filament in lamp X is the same as the filaments in the lamps in Fig. 7.1.
In Table 7.1, tick any box in the right-hand column that shows a possible difference between the filament of lamp X and a filament of one of the lamps in the circuit.
Table 7.1
[ 2 ]
4.2.4 Resistance question 2
A student is trying to determine the resistance of a lamp. He sets up the incorrect circuit shown.
Which change would allow him to take the measurements needed to calculate the resistance of the lamp?
A
Disconnect the ammeter and move it to the left of the lamp.
B
Swap the positions of the ammeter and the voltmeter in the circuit.
C
Disconnect the ammeter and connect it in parallel with the lamp.
D
Disconnect the voltmeter and connect it in parallel with the lamp.
4.2.4 Resistance question 3
The electric starter motor in a car is switched on and off using a relay.
The relay consists of a plastic case and two flexible springy strips, X and Y, which are made of soft iron. These iron strips act as the switch when a circuit is connected between the terminals W and Z.
Fig. 7.1 shows \(\mathrm{X
Fig. 7.2 shows the equipment from Fig. 7.1 inside a magnetising coil. The magnetising coil is in series with the 12 V car battery and switch S , which is open.
The power of the starter motor is 1.8 kW and it is also operated by the car battery.
The starter motor circuit is connected between terminals W and Z .
Explain why copper wires with a large cross-sectional area are used for this circuit.
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