Two electric bulbs $A$ and $B$ are marked $220\, V, 60\, W$ and $220\, V, 100\, W$ respectively. Which one of the two has greater resistance?

$(a)$ 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 meant by equivalent resistance?

How many watt-seconds are equal to $1$ unit of electrical energy?

In the following circuits (Figure),heat produced in the resistor or combination of resistors connected to a $12\, V$ battery will be

$(a)$ Name an instrument that measures electric current in a circuit. Define the unit of electric current.
$(b)$ What do the following symbols mean in an electric circuit?
$(c)$ Draw a closed circuit diagram consisting of a $0.5\, m$ long nichrome wire $XY$,an ammeter,a voltmeter,four cells of $1.5\, V$ each,and a plug key.