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The battery had a power output of 230 mW when the resistance of the variable resistor was 36 Ω - AQA - GCSE Physics - Question 7 - 2021 - Paper 1
Question 7
The battery had a power output of 230 mW when the resistance of the variable resistor was 36 Ω. Determine the potential difference across the battery. Potential di... show full transcript
Worked Solution & Example Answer:The battery had a power output of 230 mW when the resistance of the variable resistor was 36 Ω - AQA - GCSE Physics - Question 7 - 2021 - Paper 1
Step 1
Determine the potential difference across the battery.
Answer
The power output (P) of the battery is given as 230 mW, which is equivalent to 0.230 W (since 1 mW = 0.001 W). The formula relating power, current (I), and voltage (V) is:
We can rearrange this to find the potential difference:
From the graph (Figure 9), we can see that when the resistance (R) is 36 Ω, the corresponding current (I) is approximately 0.08 A.
Substituting the values:
Thus, the potential difference across the battery is approximately 2.875 V.
Step 2
Explain how Figure 9 shows that the student is correct.
Answer
The graph in Figure 9 shows that as the resistance of the variable resistor increases, the current in the circuit decreases. This relationship indicates that the current is inversely proportional to the resistance. The curve illustrates this inverse relationship clearly, supporting the student's conclusion.
Step 3
Explain how closing the switch would affect the current in the variable resistor.
Answer
When the switch is closed, it creates a short circuit in the circuit, effectively reducing the total resistance. The current through the variable resistor will be influenced because the switch's resistance is much lower than that of the variable resistor. Therefore, the overall current will increase significantly, possibly leading to almost zero resistance across the variable resistor.