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The figure shows an oscilloscope trace of a sinusoidal ac voltage - AQA - A-Level Physics - Question 29 - 2019 - Paper 2
Question 29
The figure shows an oscilloscope trace of a sinusoidal ac voltage. The time base setting is 5 ms cm⁻¹ and the Y-voltage gain is 10 V cm⁻¹. Which row describes the ... show full transcript
Worked Solution & Example Answer:The figure shows an oscilloscope trace of a sinusoidal ac voltage - AQA - A-Level Physics - Question 29 - 2019 - Paper 2
Step 1
Calculate the rms voltage
Answer
The peak-to-peak voltage can be determined from the oscilloscope trace. Given that each vertical division represents 10 V, and the maximum height of the waveform is approximately 4 cm (2 divisions), the peak-to-peak voltage (Vpp) is:
The rms voltage (Vrms) can be calculated using the formula:
V_{rms} = rac{V_{pp}}{2 ext{√2}}
Substituting the values:
V_{rms} = rac{40}{2 ext{√2}} ext{ V} = rac{40}{2.828} ext{ V} ≈ 14.14 ext{ V}
Rounding this gives us approximately 14 V.
Step 2
Calculate the frequency
Answer
The time base setting indicates that each horizontal division is 5 ms. Observing the waveform, it takes approximately 4 divisions for one complete cycle, giving a period (T):
Using the frequency formula:
f = rac{1}{T}
Calculating gives:
f = rac{1}{0.02} = 50 ext{ Hz}