How much charge passes through the starter motor? Express your answer with the a

Question

How much charge passes through the starter motor? Express your answer with the appropriate units The starter motor of a car engine draws a current of 110 A from the battery. The copper wire to the motor is 4.80 mm in diameter and 1.2 m long. The starter motor runs for 0.850 s until the car engine starts 129 Submit Previous Answers Request Answer X Incorrect; Try Again; 5 attempts remaining Part B How far does an electron travel along the wire while the starter motor is on? Express your answer with the appropriate units 0.70 mm Submit Previous Answers Request Answer X Incorrect; Try Again; 5 attempts remaining

Explanation / Answer

A) Charge passes through the starter motor is Q = i*t = 110*0.85 = 93.5 C

B) Distance travelled is D = speed*time taken

speed of the electron is vd = i/(n*e*A)

n is the free electron density of copper = 8.49*10^28 electrons/m^3

e is the charge on electron = 1.6*10^-19 C

A = pi*r^2 = 3.142*(2.4*10^-3)^2 = 1.81*10^-5 m^2

Vd = 110/(8.49*10^28*1.6*10^-19*1.81*10^-5) = 4.47*10^-4 m/s

D = Vd*t = 4.47*10^-4*0.85 = 3.8*10^-4 m

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