CAIE A-Level Physics A2 21.2.4 The Effec…moothing

[Maximum number: 6]

Fig. 5.1 shows four diodes and a load resistor of resistance $1.2 \mathrm{k} \Omega$ , connected in a circuit that is used to produce rectification of an alternating voltage.

Fig. 5.1

(a)

The output voltage in (b) is smoothed by adding a capacitor to the circuit in Fig. 5.1. The difference between the maximum and minimum values of the smoothed output voltage is 10 % of the peak voltage.

[ 6 ]

(i)

On Fig. 5.1, draw the circuit symbol for a capacitor showing the capacitor correctly connected into the circuit.

[ 1 ]

correct symbol used for capacitor and capacitor connected in parallel with the $1.2 \mathrm{k} \Omega$ resistor.

(ii)

On Fig. 5.2, sketch the variation with t of the smoothed output voltage.

[ 2 ]

straight lines or curves, with negative decreasing gradients, drawn between adjacent peaks, from top of first peak to meet
line going up to next peak
lines, from one peak to the line going up to the next peak, show a drop in p.d. of $1 \frac{1}{2}$ small squares

(iii)

Calculate the capacitance C of the capacitor.

[ 3 ]

$V=0.90 \times 6.0(=5.4 \mathrm{~V})$

or

discharge time (for each cycle) $=0.034 \mathrm{~s}$ $V=V_{0} \exp (-t / R C)$ $5.4=6.0 \exp \left[-0.034 /\left(1.2 \times 10^{3} \times C\right)\right]$ $C=2.7 \times 10^{-4} \mathrm{~F}$

CAIE A-Level Physics A2 21.2.4 The Effect of a Single Capacitor in Smoothing Topic Practice

Question 1

Question (a)

Question (i)

Question (ii)

Question (iii)