Question

An electric circuit 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 was set up.
(i) Draw a diagram of this electric circuit to study the relation between the potential difference maintained between the points 'X' and 'Y' and the electric current flowing through XY.
(ii) Following graph was plotted between V and I values:



What would be the values of $\frac{V}{I}$ rations when the potential difference is 0.8 V, 1.2 V and 1.6 V respectively?
What conclusion do you draw from these values?

(iii) What is the resistance of the wire?

Answer 1

(i)


(ii) When potential difference = 0.8 V, current = 0.32 A.
$$\begin{gathered} \frac{\mathrm{V}}{\mathrm{I}}=\frac{0.8}{0.32} \\ \frac{\mathrm{V}}{\mathrm{I}}=2.5 \end{gathered}$$
When potential difference = 1.2 V, current = 0.48 A.
$$\begin{gathered} \frac{\mathrm{V}}{\mathrm{I}}=\frac{1.2}{0.48} \\ \frac{\mathrm{V}}{\mathrm{I}}=2.5 \end{gathered}$$
When potential difference = 1.6 V, current = 0.64 A.
$$\begin{gathered} \frac{\mathrm{V}}{\mathrm{I}}=\frac{1.6}{0.64} \\ \frac{\mathrm{V}}{\mathrm{I}}=2.5 \end{gathered}$$
The V-I graph is a straight line with a constant slope of 2.5.

(iii) The resistance of the wire is 2.5 Ω.