A man monitors how much money he spends on electricity - Edexcel - GCSE Physics - Question 6 - 2015 - Paper 1
Question 6
A man monitors how much money he spends on electricity.
He uses a device which calculates the cost of electrical energy used.
He connects his 2.9 kW electric kettle ... show full transcript
Worked Solution & Example Answer:A man monitors how much money he spends on electricity - Edexcel - GCSE Physics - Question 6 - 2015 - Paper 1
Step 1
Calculate the current in the kettle element.
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Answer
To find the current in the kettle, we use the formula:
extPower(P)=extVoltage(V)imesextCurrent(I)
Here, the power of the kettle is 2.9 kW, which is equivalent to 2900 W, and the voltage is 230 V. Rearranging the formula gives us:
I=VP=230extV2900extW
Calculating this:
I≈12.61extA
Thus, the current in the kettle element is approximately 12.61 A.
Step 2
Calculate the length of time for which the kettle has been switched on during the week.
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Answer
To determine the time the kettle has been switched on, we first find the total energy used in kWh.
The total cost for the week is 97 p (pence), and we know that 1 kWh costs 17 p. The energy used can be calculated as:
Total Energy=Cost per kWhTotal Cost=17 p/kWh97 p≈5.71 kWh
Next, knowing the power rating of the kettle is 2.9 kW, we can find the time it was switched on using:
Time (h)=Power (kW)Energy (kWh)=2.9 kW5.71 kWh≈1.97 hours
Therefore, the length of time for which the kettle has been switched on during the week is approximately 1.97 hours.
