Question

O ENT ELECTRICITY ANENI ELECTRIciTY 91. The resistivity of a potentiometer wire is, if the area of cross section of the wire is 4cm the current flowing in the circuit is 1A,the potential gradient is 7.5 v/m ) 3x10Q-m 2) 2 x 10-62-m 3) 4 x 1022-m 4) 5 x 1042-m ​

Answer 1

Given :-

Area of cross section, A = 4 cm^2 = 0.0004 m^2

Current, I = 1A

Potential gradient, V/L = 7.5 v/m

To Find :-

Resistivity of potentiometer wire

Solution :-

$\tt \dfrac{V }{ L } = \dfrac{ I R}{ L}$

$: \implies \tt \dfrac{V }{ L } = \dfrac{ I \rho L}{ AL}$

$: \implies \tt \dfrac{V }{ L } = \dfrac{ I \rho }{ A}$

$: \implies \tt 7.5= \dfrac{ 1 \times \rho }{ 0.0004 }$

$: \implies \tt \rho = 7.5 \times 0.0004$

$: \implies \tt \rho = 0.003$

$: \implies \tt \bf \rho = 3×10^{-3}Ωm$

Correct option :- 1