Question

The V-I graph for four different wires of different materials having the same length and diameter are shown in the figure. Which one of the following wire has the highest resistivity?

• A. $A$
• B. $B$
• C. $C$
• D. $D$

Answer 1

The correct option is A $A$

Using Ohm's law,
$R=\frac{V}{I}$
Hence, resistance is the slope of V-I graph. Clearly, curve $A$ has the highest slope and hence, wire $A$ has the highest resistance.
Resistivity of a substance is given by:
$\rho =R\frac{A}{l}$
where:
$A$ is the cross sectional area
$l$ is the length
For the same length $l$ and area $A$
$\rho \propto R$
Therefore, wire $A$ has the highest resistivity.