The circuit shows a 1 mF capacitor connected to an a.c - Edexcel - A-Level Physics - Question 18 - 2023 - Paper 1
Question 18
The circuit shows a 1 mF capacitor connected to an a.c. supply. The graph shows how the potential difference V varies with time t.
(a) (i) Calculate the root-mean-s... show full transcript
Worked Solution & Example Answer:The circuit shows a 1 mF capacitor connected to an a.c - Edexcel - A-Level Physics - Question 18 - 2023 - Paper 1
Step 1
(i) Calculate the root-mean-square potential difference.
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Answer
To calculate the root-mean-square (RMS) potential difference for an AC voltage described by the equation V=V0imesextsin(heta), we use the formula:
Vrms=2V0
In this case, the maximum voltage V0 is given as 5 V. Therefore, substituting this value:
Vrms=25≈3.54 V
Step 2
(ii) Explain why this formula leads to the graph above.
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Answer
The formula V=5sin(100πt) describes a sinusoidal wave with a maximum amplitude of 5 V. The term 100π indicates the angular frequency of the waveform, which determines how fast the wave oscillates. This results in a periodic graph, depicting the voltage as it varies over time.
Amplitude and Periodicity: The graph shows that the voltage oscillates between +5 V and -5 V, reflecting the maximum amplitude given by the formula.
Frequency: The frequency of the graph can be found from the coefficient of t in the sine function. In this case, the angular frequency ω=100π leads to a frequency of f=2πω=50 Hz, indicating the rapid oscillation.
Negative Values: The sine function's nature allows for both positive and negative values, which is clearly illustrated in the graph as the voltage dips below 0 V, demonstrating the alternating nature of the current.