Which of the following has the unit $volt$?

What is the unit of electric current?

If the diameter of a conducting wire is doubled,how many times does its resistance become?

State Ohm's law. How can it be verified experimentally? Does it hold good under all conditions? Comment.

An electric bulb is rated at $200 \ V - 100 \ W$. What is its resistance? If five such bulbs burn for $4 \ hours$, what is the total electrical energy consumed? Calculate the cost, if the rate is $50$ paise per unit.

$(a)$ Explain how a cell maintains current in a circuit.
$(b)$ In the circuit given below,the resistance of the path $xTy = 2 \, \Omega$ and that of $xZy = 6 \, \Omega$.
$(i)$ Find the equivalent resistance between $x$ and $y$.
$(ii)$ Find the current in the main circuit.
$(iii)$ Calculate the current that flows through the path $xTy$ and $xZy$.