Question

Physic
A copper wire of radius 0.1 mm and resistance 1 k ohm is connected across a power supply of 20 V
(1) How many electrons are transferred per second?
between the supply and the wire at one end?
(ii)Write down the current density in the wire.​

Answer 1

Sol.

r = 0.1 mm = 10^-4

R = 1 KΩ = 10^3 Ω,

V = 20 V

a) No.of electrons transferred

i = V/R = 20/10^3 = 20 * 10^-3 = 2 * 10^-2 A

q = i t = 2 * 10^-2 * 1 = 2 * 10^-2 C.

No. of electron transferred = 2 * 10^-2/1.6 * 10^-19 = 2 * 10^-17/1.6 = 1.25 * 10^17.

b)Current density of wire = i/A = 2 * 10^-2/π * 10^10^-8

= 2/3.14 * 10^+6 0.6369 * 10^+6

= 6.37 * 10^5 A/m^2.