Current Electricity 1 Question 21
21. The current-voltage graphs for a given metallic wire at two different temperatures $T _1$ and $T _2$ are shown in the figure.
The temperature $T _2$ is greater than $T _1$
$(1985,3 M)$
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Solution:
- $\frac{I}{V}=$ slope of given graph $=\frac{1}{R} \quad$ or $\quad R=\frac{1}{\text { slope }}$
Resistance of a metallic wire increases with increase in temperature.
$$ \begin{array}{rlrl} & & (\text { slope }) _{T _2} & <(\text { slope }) _{T _1} \\ \therefore & \frac{1}{(\text { slope }) _{T _2}} & >\frac{1}{(\text { slope }) _{T _1}} \\ \text { or } \quad R _{T _2} & >R _{T _1} \text { or } T _2>T _1 \end{array} $$
