Physics 9702 · AS & A Level · Rectification and smoothing

Rectification and smoothing — practice question

Fig. 6.1 depicts part of a bridge rectifier circuit that may be used to rectify an alternating input voltage $V_{\mathrm{IN}}$. Four diodes are present in the circuit, and one is drawn. The rectified output voltage $V_{\mathrm{OUT}}$ is applied across load resistor $R$.
(a(i))[1]

State the meaning of rectification.

(a(ii))[1]

State the name of the type of rectification given by a bridge rectifier circuit.

(a(iii))[2]

Complete the circuit in Fig. 6.1 by drawing the three absent diodes inside the dashed circles.

(b(i))[2]

The input voltage changes with time $t$ according to the equation $V_{\mathrm{IN}} = 34\sin 18t$, where $V_{\mathrm{IN}}$ is in V and $t$ is in s. Show that the period of the input voltage is $0.35\,\text{s}$.

(b(ii))[1]

Calculate the root-mean-square (r.m.s.) input voltage.

(b(iii))[3]

On Fig. 6.2, sketch how $V_{\mathrm{OUT}}$ varies with $t$ from $t=0$ to $t=0.35\,\text{s}$.

(c(i))[1]

The resistance of resistor $R$ is $56\,\text{k}\Omega$. A capacitor with capacitance $12\,\mu\text{F}$ is added to the circuit of Fig. 6.1 to smooth the output voltage. On Fig. 6.1, draw the capacitor connected correctly into the circuit.

(c(ii))[2]

Calculate the time constant of the smoothing circuit.

(c(iii))[2]

During each discharge cycle, the capacitor spends $0.14\,\text{s}$ discharging. Determine the minimum value of the smoothed output voltage.

Worked solution & mark scheme

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