A heating coil can heat the water of a vessel from $20\,^oC$ to $60\,^oC$ in $30$ minutes. Two such heating coils are put in series and then used to heat the same amount of water through the same temperature range. The time taken now will be ............ $min$ (neglecting thermal capacity of the coils)

An electric bulb is rated $220\, volt$ and $100\, watt$. Power consumed by it when operated on $110\, volt$ is ............. $watt$

Three identical bulbs are connected as shown in figure. When switch $S$ is closed, the power consumed in bulb $B$ is $P$. What will be the power consumed by the same bulb when switch $S$ is opened?

Two bulbs of equal wattage, one having carbon filament and the other having a tungsten filament are connected in series to the mains, then

The emf of a battery is $2\, V$ and its internal resistance is $0.5 \,\Omega$. The maximum power which it can deliver to any external circuit will be ............. $watt$

You are given a resistance wire of length $50\, cm$ and a battery of negligible resistance. In which of the following cases is largest amount of heat generated