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

To calculate the power supplied to the headlamp, we use the formula:

Substituting the given values:

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

The total current in the wires to the battery can be calculated by summing the currents of all the devices. Given that the headlamp uses 4.8 A, the interior light uses 0.6 A, the heater uses 10 A, and the radio uses 2.3 A, we have:

Therefore, the current in the wires to the battery when all devices are switched on is 17.7 A.

When any one of the devices is switched off, the overall resistance of the circuit increases. This is because the total current flowing through the circuit decreases, leading to a higher resistance according to Ohm's Law, where $R = \frac{V}{I}$.

The technician should choose a 5 A fuse to protect the radio circuit, as it is slightly above the current rating of 2.3 A, providing adequate protection while allowing normal operation.

The wires to the battery in a car are thicker because they need to carry a higher current. Thicker wires have lower resistance, which prevents overheating and ensures efficient energy transfer from the battery to all connected devices. In contrast, the wires connecting each device to its switch and fuse carry lower currents, allowing for thinner wires to be sufficient.