The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance…

The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of $100 \mathrm{~W}$ and $200 \mathrm{~V}$ lamp when not in use?
  1. $40 \Omega$
  2. $20 \Omega$
  3. $400 \Omega$
  4. $200 \Omega$

Solution

$R_{\text {hot }}=\frac{V^2}{P}=\frac{200 \times 200}{100}=400 \Omega$ cold resistance $=R_{\text {hot }} / 10=400 / 10=40 \Omega$

Asked in: JEE Main 2005

Practice more Current Electricity questions on Aicharya