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A student uses a red hosepipe to make a solar water heater - Edexcel - GCSE Physics - Question 2 - 2018 - Paper 1
Question 2
A student uses a red hosepipe to make a solar water heater. The hosepipe is full of water. The student coils the hosepipe and fixes it into a clear plastic box as sh... show full transcript
Worked Solution & Example Answer:A student uses a red hosepipe to make a solar water heater - Edexcel - GCSE Physics - Question 2 - 2018 - Paper 1
Step 1
The student now paints the hosepipe to make it more efficient at absorbing heat. Which of these coloured paints would be the best to use? Put a cross (X) in the box next to your answer.
Answer
The best color to paint the hosepipe is A. Black. Black surfaces absorb more heat compared to other colors, making them more efficient for solar energy absorption.
Step 2
Explain what happens to the temperature of the water in the hosepipe during the day, from sunrise to sunset.
Answer
As the sun rises, the temperature of the water in the hosepipe will gradually increase because the solar energy heats the water. After reaching a peak during midday when sunlight is strongest, the temperature will remain fairly constant. As the sun sets, the temperature will begin to decrease as the hosepipe no longer receives direct sunlight.
Step 3
Calculate the efficiency of the heater.
Answer
To calculate the efficiency of the heater, we use the formula:
The energy absorbed can be calculated as:
Energy absorbed = Energy incident - Energy reflected = 15000 J - 6000 J = 9000 J
Now substituting in the formula:
Therefore, the efficiency of the heater is 60%.