If a power of $100\, W$ is being supplied across a potential difference of $200\, V$, current flowing is ............ $A$
$2$
$0.5$
$1$
$20$
A constant voltage is applied between the two ends of a metallic wire. If both the length and the radius of the wire are doubled, the rate of heat developed in the wire
An electric bulb is rated $60\,W$, $220\,V$. The resistance of its filament is ............. $\Omega$
If in the circuit, power dissipation is $150\, W$, then $R$ is ............... $\Omega$
Two electric bulbs marked $40\,W,$ $220\,V$ and $60\,W,\,\,220\,V$ when connected in series across same voltage supply of $220\,V,$ the effective power is $P_1$ and when connected in parallel, the effective power is $P_2.$ Then $\frac {P_1}{P_2}$ is
A heater of $220\, V$ heats a volume of water in $5\,\min$ time. A heater of $110\, V$ heats the same volume of water in ............... $min$