A student connects an electric fire to the mains supply. The power rating of the fire is 2.5 kW. a) (i) Complete the sentence by putting a cross (X) in the box next to your answer. A power of 2.5 kW is the same as ☐ A 2500 amps per volt ☐ B 2500 joules per amp ☐ C 2500 joules per second ☐ D 2500 joules per volt (ii) 1 kWh of electricity costs 20p. Calculate the cost of keeping the fire on for 12 minutes.

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A student connects an electric fire to the mains supply - Edexcel - GCSE Physics - Question 3 - 2017 - Paper 1

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A student connects an electric fire to the mains supply. The power rating of the fire is 2.5 kW. a) (i) Complete the sentence by putting a cross (X) in the box nex... show full transcript

Worked Solution & Example Answer:A student connects an electric fire to the mains supply - Edexcel - GCSE Physics - Question 3 - 2017 - Paper 1

Step 1

Complete the sentence by putting a cross (X) in the box next to your answer.

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Answer

A power of 2.5 kW is the same as D 2500 joules per volt.

This is because power (in watts) can be expressed as energy (in joules) per unit time (in seconds), leading to the relationship:

$ext{Power} = rac{ ext{Energy}}{ ext{Time}}$ Hence, 2.5 kW is equivalent to 2500 joules per second.

Step 2

Calculate the cost of keeping the fire on for 12 minutes.

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Answer

First, convert minutes to hours:

$ext{Time in hours} = rac{12}{60} = 0.2 ext{ hours}$

Now, calculate the energy consumed:

$ext{Energy (kWh)} = ext{Power (kW)} imes ext{Time (h)} = 2.5 ext{ kW} imes 0.2 ext{ h} = 0.5 ext{ kWh}$

Finally, compute the cost:

$ext{Cost} = ext{Energy (kWh)} imes ext{Cost per kWh} = 0.5 ext{ kWh} imes 20 ext{p} = 10 ext{p}$

Therefore, the total cost of keeping the fire on for 12 minutes is 10 pence.

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