$(a)$ $(i)$ What is meant by saying that the potential difference between two points is $1$ volt ?

$(ii)$ How much energy is given to $5$ coulomb of charge passing through a $12 \,V$ battery ?

$(b)$ Describe an activity with necessary electric circuit drawn to study the factors on which the resistance of a conducting wire depends.

$(a)$ $(i)$ It means that the work done in moving a charge of $1$ coulomb between the two points is $1$ joule.

$(ii)$ Using the expression

$W=q V=5 \times 12=60 J$

$(b)$ Complete an electric circuit consisting of a cell, an ammeter, a nichrome wire of length $l$ [say, marked (1)] and a plug key, as shown in Fig.

$(i)$ Now, plug the key. Note the current in the ammeter.

$(ii)$ Replace the nichrome wire by another nichrome wire of same thickness but twice the length; that is $2 l$ [marked $(2)$ in the Fig.].

$(iii)$ Note the ammeter reading.

$(iv)$ Now, replace the wire by a thicker nichrome wire, of the same length $l$ [marked $(3)].$ A thicker wire has a larger cross-sectional area. Again, note down the current through the circuit.

$(v)$ Instead of taking a nichrome wire, connect a copper wire [marked $(4)$ in Fig.] in the circuit. Let the wire be of the same length and same area of crosssection as that of the first nichrome wire [marked $(1)].$ Note the value of the current.

$(vi)$ Notice the difference in the current in all cases.

One will notice that the current in all the three cases is different. This shows that the resistance depends upon a number of factors.