Which physical quantity has a unit of $kWh$?

State the factors on which the heat produced in a current-carrying conductor depends. Give one practical application of this effect.

In an experimental set-up as shown below,a piece of silver was placed touching points $A$ and $B$. Next time it was replaced by a piece of wood. In which case did the bulb glow? Give reason to justify the observation.

Two bulbs are marked $60\, W, 220\, V$ and $100\, W, 220\, V$. These are connected in parallel to a $220\, V$ mains. Which one out of the two will glow brighter?

$A$ $4 \, \Omega$ resistance wire is doubled on itself. Calculate the new resistance of the wire.

$(a)$ Explain why a conductor offers resistance to the flow of current.
$(b)$ Differentiate between conductor,resistor,and resistance.