Paper 4 Alternating Current Drills

Q1 Oscilloscope Measurement

The oscilloscope trace below is centred on the zero-voltage line. The vertical sensitivity is $1.5\mathrm{V}\mathrm{divisio}{\mathrm{n}}^{-1}$ and the time-base setting is $0.50\mathrm{ms}\mathrm{divisio}{\mathrm{n}}^{-1}$.

1. Determine the peak voltage $V_0$. [2]
2. Determine the period $T$ and frequency $f$. [3]
3. Assuming the waveform is sinusoidal, calculate $V_{\mathrm{rms}}$. [2]
4. Explain why measuring the horizontal length of several complete cycles can reduce the percentage uncertainty in $T$. [2]
5. State one adjustment that would improve reading precision without clipping the trace. [1]

Q2 Rectifier Output Investigation

1. Describe how to compare half-wave and full-wave rectified outputs using an oscilloscope. [2]
2. State how adding a capacitor changes the trace. [2]
3. State one safety precaution when using mains-powered equipment. [1]