Calculate the number of electrons constituting one coulomb of charge. (Charge on one electron $= 1.6 \times 10^{-19} \text{ C}$)

How many electrons constitute a total charge of $1 \ C$?

$(a)$ Three resistors $R_{1}, R_{2}$ and $R_{3}$ are connected in parallel and the combination is connected to a battery,ammeter,voltmeter,and key. Draw a suitable circuit diagram. Obtain an expression for the effective resistance of the combination of resistors in parallel.
$(b)$ Why are electric bulbs filled with chemically inactive nitrogen or argon?
$(c)$ What is meant by the statement that the rating of a fuse in a circuit is $5 \ A$?

What is the $SI$ unit of electric charge?

What will happen to the current in a circuit,if its resistance is doubled?

The equivalent resistance between points $A$ and $B$ in the following electric circuit is: