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An uncharged capacitor is connected to a power supply which supplies a constant current of 10 μA - AQA - A-Level Physics - Question 19 - 2020 - Paper 2

Question 19

An uncharged capacitor is connected to a power supply which supplies a constant current of 10 μA. After 100 ms, the potential difference across the capacitor is 5.0 ... show full transcript

Worked Solution & Example Answer:An uncharged capacitor is connected to a power supply which supplies a constant current of 10 μA - AQA - A-Level Physics - Question 19 - 2020 - Paper 2

Step 1

Calculate the Charge Stored in the Capacitor

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Answer

The charge ( Q ) stored in a capacitor can be calculated using the formula:

$Q = I imes t$

where:

$I$ is the current (10 μA = $10 imes 10^{-6} A$ )
$t$ is the time in seconds (100 ms = $0.1 s$ )

Substituting the values:

$Q = 10 imes 10^{-6} imes 0.1 = 10 imes 10^{-7} C = 1.0 imes 10^{-6} C$

Step 2

Use the Capacitance Formula

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Answer

The capacitance ( C ) is related to the stored charge and the potential difference ( V ) across the capacitor by the formula:

$C = \frac{Q}{V}$

Given the potential difference, V = 5.0 kV = 5000 V, we can now calculate the capacitance:

$C = \frac{1.0 imes 10^{-6}}{5000} = 2.0 imes 10^{-10} F$

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