Question

The resistance of 5 m length of a wire of the same material but with twice of the area of cross section.
​

Answer 1

Answer:

In the question, it is given that the resistance of one meter wire is 3 ohms. So the resistance of 1.5 meters of the same wire is given as

1

3×5

=15ohms.

The resistance of a resistor is given by the formula R=ρ

A

L

where ρ is the resistivity of the material the resistor is made of, l is the length of the resistor and A is the cross-sectional area.

Let the resistance of the wire is initially equal to R. R=ρ

A

L

.

When the area of cross-section of the wire is doubled and so the resistance of the wire is given as R

′

=ρ

2(A)

L

.

The new resistance is R

′

=

2

R

.

Hence, the changed resistance of the wire is 15/2=7.5 ohms.