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A technician investigates different electrical devices that are used in a car - Edexcel - GCSE Physics Combined Science - Question 5 - 2021 - Paper 1
Question 5
A technician investigates different electrical devices that are used in a car. The technician connects a device to the 12V car battery. The technician measures the c... show full transcript
Worked Solution & Example Answer:A technician investigates different electrical devices that are used in a car - Edexcel - GCSE Physics Combined Science - Question 5 - 2021 - Paper 1
Step 1
(a) (i) Draw on Figure 8 to show how the circuit should be completed so that the current in the circuit and voltage across the device can be measured.
Answer
To complete the circuit in Figure 8, draw a voltmeter in parallel with the device being tested to measure the voltage across it. Additionally, ensure that an ammeter is connected in series with the device to measure the current flowing through it.
Step 2
(a) (ii) The technician tests a headlamp. The current in the headlamp is 4.8 A when connected to the 12V battery. Calculate the power supplied to the headlamp.
Answer
To calculate the power supplied to the headlamp, use the formula:
where:
- is the power in watts (W)
- is the voltage in volts (V), which is 12V in this case
- is the current in amperes (A), which is 4.8A
Substituting the known values:
Thus, the power supplied to the headlamp is 58 W.
Step 3
(b) (i) Calculate the current in the wires to the battery when all the devices are switched on.
Answer
To find the total current in the wires to the battery when all devices are switched on, add up the currents of each device:
- Headlamp: 4.8 A
- Interior Light: 0.6 A
- Heater: 10 A
- Radio: 2.3 A
Total current:
Therefore, the current in the wires to the battery is 17.7 A.
Step 4
(b) (ii) State how the overall resistance of the circuit changes when any one of the devices is switched off.
Answer
When any one of the devices is switched off, the overall resistance of the circuit increases. This is because removing a device from the circuit reduces the total current flowing, as per Ohm's law (R = rac{V}{I}). If the voltage remains constant and the current decreases, the resistance must increase.
Step 5
(b) (iii) There is a current of 2.3 A in the radio when the radio is working correctly. Which of these should the technician choose to protect the radio circuit?
Answer
The technician should choose a 5 A fuse to protect the radio circuit. This provides a safe margin above the 2.3 A current while ensuring that the fuse will blow if the current exceeds safe limits.
Step 6
(b) (iv) Explain why the wires to the battery in a car are thicker than the wires that connect each device to its switch and its fuse.
Answer
The wires leading to the battery in a car are thicker because they need to carry a higher current to power multiple devices simultaneously. Thicker wires have lower resistance, which reduces heat generation and minimizes voltage drop, making them better suited for handling the high currents associated with starting the engine and powering major electrical systems.