Question

what length of resistance wire of resistivity hundred into 10 to the power minus 8 ohm metre area of cross section 2.5 into 10 to the power minus 7 metre square would be needed to make a resistor of 57.6 ohm​

Answer 1

Explanation:

Potential Gradient (x) = Potential drop per unit length

x=

l

v

V = Potential Difference

L = length.

⇒R=

A

ρl

ρ = specific resistance

A = Area

x=

l

ir

=

la

iρl

=

l

iρ

x=

8×10

−7

0.2×4×10

−7

=0.1units

Answer 2

Solution:

let, R be the resistance of the wire.

A be the area of cross section of the wire.

L be the length of the wire and

p be the resistivity of the wire.

here, given in the question that

resistivity of the wire is hundred into 10 to the power minus 8 ohm meter

so, p = 100*10^-8 ohm m

area of cross section of the wire is 2.5 into 10 to the power minus 7 meter square.

so, A = 2.5*10^-7 m^2

resistance of the wire is 57.6 ohm.

so, R = 57.6 ohm.

now, we know that

R = p L/A

L = RA/p

L = 57.6*2.5*10^-7/100*10^-8

L = 144/10

L = 14.4 m