An expression for the rate of heat generated,if a current of $I$ ampere flows through a resistance of $R$ $\Omega$,is

$A$ $100\, W$ bulb working on $200\, V$ and a $200\, W$ bulb working on $100\, V$ have:

$A\, 5\, ^oC$ rise in the temperature is observed in a conductor by passing some current. When the current is doubled,then the rise in temperature will be equal to ............. $^oC$.

$A$ piece of fuse wire melts when a current of $15\, A$ flows through it. With this current,if it dissipates $22.5\, W$,the resistance of the fuse wire will be .............. $\Omega$.

Two electric bulbs of $40 \text{ W}$ each are connected in series. The power consumed by the combination will be . . . . . . . (in $\text{ W}$)

What is the value of $1 \, kWh$ in Joules?