Question

A current of 4 A flows through a nichrome wire under a
P.D. of 4V. If the length of the nichrome wire is 1 m and
its area of cross section is 1 mm², then its resistivity is
(a) 2 x 10-6 m (b) 2 x 10-72m
(C) 10-62 m
(d) 5 x 10-722-m​

Answer 1

Answer:

Resistance of the wire

R=

I

V

∴ R=

4

2

=

0.5

A

Cross-section area of wire

A=

1mm

2

=

10

−6

m

2

Length of wire

L=

1m

Thus resistivity of wire

ρ=

L

RA

∴ ρ=

1

0.5×10

−6

=

5×

10

−7

Ωm

Answer 2

The correct option is (c) 10^(-6) ohm-m

Given:

I = 4A

V = 4V

L = 1m

A = 10^(-6) m²

To Find:

The resistivity of the nichrome wire

Solution:

Resistance in the wire flowing with the current, I under potential difference, V is given by;

R = V / I

R = 4 / 4 = 1 ohm

Now, the resistivity of the wire

$= \frac{RA}{L} \\=\frac{1ohm \times 10^{-6}m^{2} }{1m}\\ =10^{-6} ohm-m$

Hence, the correct option is (C) 10^-6 ohm-m

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