An electric room radiator which operates at $225\, V$ has a resistance of $50\, \Omega$. The power of the radiator is approximately ............... $W$.

$A$ constant voltage is applied between two ends of a metallic wire. If the length is halved and the radius of the wire is doubled,the rate of heat developed in the wire will be

In a building,there are $15$ bulbs of $45 \; W$,$15$ bulbs of $100 \; W$,$15$ small fans of $10 \; W$,and $2$ heaters of $1 \; kW$. The voltage of the electric main is $220 \; V$. The minimum fuse capacity (rated value) of the building will be: .......... $A$

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

Two electric bulbs $A$ and $B$ are rated as $60\, W$ and $100\, W$. They are connected in parallel to the same source. Then,

$A$ resistor develops $300 \,J$ of thermal energy in $15 \,s$,when a current of $2 \,A$ is passed through it. If the current increases to $3 \,A$,the energy developed in $10 \,s$ is........$J.$