American Bulb in India

Electricity and Magnetism Level 4

A bulb is designed to consume $60 \ \text{W}$ of power when operated at $120 \ \text{V}$ (residential voltage in the US).

It is brought to India, and connected to the mains (voltage $230 \ \text{V}$ , frequency $50 \ \text{Hz}$ ).

A choke needs to be connected to the bulb in series so that it works properly.

Find the inductance (in henry) of the coil of the choke.

$\textbf{Assumptions}$

Assume that the plug type is same in the US and in India.
The mains in both the countries have AC current, and the voltages given are rms voltages.

1 solution

Ronak Agarwal
Sep 16, 2014

For bulb to be working properly we have current through the bulb to be same.

Initially the current through the bulb is $=\frac{P}{V}=0.5 A$

Also the resistance is $R=\frac{V}{I}=0.5 \Omega$

After the current should be $0.5 A$

Given voltage is $230 V$ hence the impedance should be $Z=\frac{V}{I}=460 \Omega$

$Z=\sqrt{{R}^{2}+{\omega L}^{2}}$ Putting the values we get :

$\omega L = 392.428 \Omega$

Given $f=50Hz$ and $\omega = 2\pi f$ . Solving for L we get :

$L=1.249$ Henry