Question

A bulb is designed to work with peak voltage 45V and period 28ms. It has resistance 120 Ohms and is in series with a 5.1 kiloohms resistor and an AC power supply.

Complete the following:

a) Sketch and label the circuit diagram

b) The frequency of the power supply

c) The peak current through the bulb

d) The voltage RMS of the power supply

Answer 1

a)

b) We are given time period 28 ms

frequency= 1/time period = 1/0.028 = 35.7 Hz

c) peak current = peak voltage /resistance = 45/120 = 0.375 ampere

d) RMS voltage = Peak voltage/$\sqrt2$ = 45/$\sqrt2$ volts