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A student has a battery-powered torch - Edexcel - GCSE Physics - Question 6 - 2017 - Paper 1
Question 6
A student has a battery-powered torch. When the lamp in the torch is lit for 10 s, 9 J of energy is transferred in a useful way and 61 J is wasted. Complete the tabl... show full transcript
Worked Solution & Example Answer:A student has a battery-powered torch - Edexcel - GCSE Physics - Question 6 - 2017 - Paper 1
Step 1
Complete the table:
Answer
- Thermal (heat): 61 J
- Light: 9 J
- Electrical: 70 J
Explanation: The total energy supplied to the torch is the sum of useful energy and wasted energy:
So,
This shows that in the 10 seconds:
- 61 J is transferred as thermal energy,
- 9 J as light energy,
- and the total electrical energy supplied is 70 J.
Step 2
Explain why the temperature of the filament in the lamp remains the same:
Answer
The temperature of the filament remains constant because it has reached a steady state where the rate of energy being supplied by the electricity is equal to the rate of energy lost to the surrounding environment through radiation and conduction. Although electricity is still being supplied, the filament dissipates heat energy at the same rate, maintaining a constant temperature. This equilibrium ensures that any additional energy input is countered by an equal amount of energy output.