-How long does it take electrons to get from a car battery to the starting motor

Question

-How long does it take electrons to get from a car battery to the starting motor? Assume the current is 300 A and the electrons travel through a copper wire with cross-sectional area 0.120 cm2 and length 0.970 m. The number of charge carriers per unit volume is 8.49

How long does it take electrons to get from a car battery to the starting motor? Assume the current is 300 A and the electrons travel through a copper wire with cross-sectional area 0.120 cm2 and length 0.970 m. The number of charge carriers per unit volume is 8.49 times 1028 m-3.

Explanation / Answer

The electrons will travel at drift velocity Vd

Vd = I/nAq

I = 300 A

n = 8.49 * 10^28 m^-3

A = 0.120 * 10^-4 m^2

q = 1.6 * 10 ^-19 C

Vd = 1.84 mm/s

Time taken = D/Vd = 970 mm/1.84 mm/s = 527 seconds

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