Awire with a length of 150 m and a radius of 0.15 mm carries a current with a uniform current density of 2.8 x 10^7a/m^2. the current is: a) 2.0 a b) 0.63 a c) 5.9a d) 300 a e) 26000 a

The current is 2.0 A.

(A) is correct option.

Explanation:

Given that,

Length = 150 m

Radius = 0.15 mm

Current density

We need to calculate the current

Using formula of current density

Where, J = current density

A = area

I = current

Put the value into the formula

Hence, The current is 2.0 A.

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .