Question

(ii) How does the current density varies if area is doubled? (a) p becomes half (b) p will be doubled (c) p doesn't vary. (d) p is only depend on current ​

Answer 1

Here, the current I, in a wire is doubled keeping temperature constant. Hence the current density J, will also be doubled since, J=

Area

I

.

Also, the drift velocity V

d

, will also be doubled since, I=neAV

d

The mean time between collisions is constant since it is independent of current.

And, the number of electrons per unit volume in a conductor remains invariant for change in current

Answer 2

If area is doubled, current density (a) ρ becomes half.

Explanation:

• Current density is defined as the amount of electric current flowing through a unit cross-sectional area.
• It is a vector quantity. The SI unit of electric current density is ampere per square meter.

• More the current in a conductor, higher will be the current density.

• Current density $=\frac{current}{area}$

• Current density is directly proportional to current and inversely proportional to the cross sectional area.

• If area is doubled, then current density becomes half.