A technician investigates different electrical devices that are used in a car - Edexcel - GCSE Physics Combined Science - Question 5 - 2021 - Paper 1

The power supplied to the headlamp can be calculated using the formula:

$P = IV$

Where:

• $I = 4.8 \, A$ (current in the headlamp)
• $V = 12 \, V$ (voltage from the battery)

Substituting the values:

$P = 4.8 \, A \times 12 \, V = 57.6 \, W$

Thus, the power supplied to the headlamp is approximately 58 W.

To find the total current when all devices are switched on, sum the individual currents:

• Headlamp: 4.8 A
• Interior Light: 0.6 A
• Heater: 10 A
• Radio: 2.3 A

Thus,

$I_{total} = 4.8 \, A + 0.6 \, A + 10 \, A + 2.3 \, A = 18.7 \, A$

Therefore, the total current in the wires to the battery is 18.7 A.

When any one of the devices is switched off, the overall resistance of the circuit increases. This occurs because the total current decreases due to the open circuit created by turning off a device.

The technician should choose a 5 A fuse to protect the radio circuit. Since the current in the radio is 2.3 A, a 5 A fuse provides adequate protection without blowing during normal operation.

The wires leading to the battery are thicker to handle high currents without overheating. Thicker wires have lower resistance, which minimizes energy loss as heat, ensuring efficient power distribution across the various devices.