Question

How long does it take electrons to get from a car battery to the starting motor? Assume the current is 260 A and the electrons travel through a copper wire with cross-sectional area 0.200 cm2 and length 1.00 m. The number of charge carriers per unit volume is 8.49 × 1028 m-3.

Answer 1

Answer:

17.41 minutes

Explanation:

i = 260 A

A = 0.2 cm^2 = 0.2 x 10^-4 m^2

l = 1 m

n = 8.49 x 10^28 per cubic meter

Let the drift velocity is vd.

The relation between the current and the drift velocity os given by

i = n e A vd

260 = 8.49 x 10^28 x 1.6 x 10^-19 x 0.2 x 10^-4 x vd

vd = 9.57 x 10^-4 m/s

Let the time taken be t

time = distance / speed

t = l / vd = 1 / (9.57 x 10^-4) = 1044.93 seconds = 17.41 minutes