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... 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
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.
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Answer
To complete the circuit, add an ammeter in series with the device and a voltmeter in parallel across the device. This configuration allows for the measurement of both current and voltage.
Step 2
Calculate the power supplied to the headlamp.
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Answer
Using the formula for power, which is:
P=VI
where V=12V and I=4.8A, we can substitute the values:
P=12imes4.8=57.6W
Thus, the power supplied to the headlamp is approximately 58 W.
Step 3
Calculate the current in the wires to the battery when all the devices are switched on.
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Answer
To find the total current in the wires to the battery, sum the individual currents:
4.8A+0.6A+10A+2.3A=17.7A
Therefore, the total current is 17.7 A.
Step 4
State how the overall resistance of the circuit changes when any one of the devices is switched off.
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Answer
When one device is switched off, the overall resistance of the circuit increases because the total current decreases, following Ohm's Law, V=IR. With the total voltage remaining constant, an increase in resistance results from a decrease in total current.
Step 5
Which of these should the technician choose to protect the radio circuit?
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Answer
The correct choice would be a C 10 A fuse, as it is greater than the 2.3 A current in the radio, providing adequate protection without blowing under normal operation.
Step 6
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.
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Answer
The wires to the battery need to carry a larger current and provide power to multiple devices, which requires a greater cross-sectional area to prevent overheating and allow for efficient energy transfer. Thicker wires have lower resistance and can handle higher currents safely.
