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
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B
B
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C
C
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D
D
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Solution
The correct option is AA Using Ohm's law, R=VI 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: ρ=RAl where: A is the cross sectional area l is the length For the same length l and area A ρ∝R Therefore, wire A has the highest resistivity.