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CAIE IGCSE Physics Resistance Length and Cross-Sectional Area

Practise applying resistance proportional to length and inversely proportional to cross-sectional area, converting diameter changes into area factors for wires.

Syllabus
2026–2028
Course
Physics 0625

Exam points

  • apply R proportional to length so multiplying a wire's length multiplies its resistance equally
  • apply R proportional to 1/A and square any diameter factor before changing the resistance
  • combine length and area ratios to calculate or rank resistances for wires of the same material

4.2.4.5—Following relationship for a metallic question 1

[Maximum number: 2]

Fig. 7.1 shows three identical lamps and an ammeter connected to a power supply.

Fig. 7.1

Fig. 7.1

The switches are closed. Each lamp is rated at 60 W and operates at its normal working voltage of 110 V .

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

Table 7.1

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