Diodes and their applications

Explanation of question 11

A bleeder resistor is connected across a smoothing capacitor in a power supply unit. Its purpose is to

1. give additional smoothing when the supply is switched off
2. increase the ripple frequency
3. reduce the ripple frequency
4. discharge the capacitor when the supply is switched off

The answer is :- 4 As a safety precaution, a resistor should be connected across the capacitor to ‘bleed’ any charge away. Its value should be sufficiently low to do this in a short time. A time constant (RC) no greater than one second is recommended.