$Kilowatt-hour$ $(kWh)$ is a unit of

$A$ heating element is designed to dissipate $2400 \, W$ when connected to $240 \, V$. The power it dissipates when it is connected to $120 \, V$ is (Assume that resistance of the filament is constant). (in $ \, W$)

Find the number of electrons flowing through the filament of a $120 \ V, 60 \ W$ electric lamp in one second.

By what percentage will the illumination of the lamp decrease if the current drops by $20 \%$ (in $\%$)?

Two bulbs are rated $(40 \; W, 200 \; V)$ and $(100 \; W, 200 \; V)$. What is the correct relation for their resistances?

The same mass of copper is drawn into two wires $1 \, mm$ and $2 \, mm$ thick. Two wires are connected in series and current is passed through them. The ratio of heat produced in the wires is: