An electric bulb rated as \[500\,\,W-100\,\,V\] is used in a circuit having \[200\,\,V\] supply. The resistance \[R\] that must be put in series with the bulb, so that the bulb draws \[500\,\,W\] is
A)\[100\Omega \]
B)\[50\Omega \]
C)\[20\Omega \]
D) \[10\Omega \]
Correct Answer:
C
Solution :
We know that,\[P=Vi\] \[\therefore \]Current through the circuit, \[i=\frac{500}{100}=5\,\,A\] Potential difference across,\[R=100\,\,V\] \[\therefore \]Relation,\[V=IR\] \[100=5\times R\] \[\Rightarrow \] \[R=\frac{100}{5}=20\Omega \]