Question

Find the equivolent resistonce of the
following, system and total
current passing through it .
The specific resistance of the material of wire is 3 x 10-7 ohm m. If the resistance of the
wire is 4 ohm and radius of the wire is 0.6 mm, calculate the length of the wire.​

Answer 1

Step 1: The resistance of wire is expressed as

R=

A

ρL

....(1)

Given, R=1Ω,

The area of cross section, A=πr

2

=3.14×0.001

2

=3.14×10

−6

.

Resistivity ρ=1.7×10

−8

ohm-meter

Step 2: Putting above values in equation (1)

We get

1=

3.14×10

−6

1.7×10

−8

×L

⇒L=

1.7×10

−8

1×3.14×10

−6

=

1.7×10

−8

3.14×10

−6

=1.847×10

2

m.

Therefore, the length of the wire is 184.7 meters.

Hence, Option A is correct.