Question

He starter motor of a car engine draws a current of 170 AA from the battery. The copper wire to the motor is 6.00 mmmm in diameter and 1.2 m long. The starter motor runs for 0.760 ss until the car engine
A)How much charge passes through the starter motor? (C)
B)How far does an electron travel along the wire while the starter motor is on?(mm)

Answer 1

Answer:

129.2 C

0.33758239177 mm

Explanation:

n = Number density = $8.46\times 10^{28}\ electrons/m^3$

i = Current = 170 A

t = Time taken = 0.76 s

d = Diameter = 6 mm

Charge is given by

$q=it\\\Rightarrow q=170\times 0.76\\\Rightarrow q=129.2\ C$

The charge passing throught the motor is 129.2 C

Current density

$J=\dfrac{i}{A}\\\Rightarrow J=\dfrac{170}{\dfrac{\pi}{4}\times (6\times 10^{-3})^2}\\\Rightarrow J=6012520.07236\ A/m^2$

Drift velocity is given by

$v_d=\dfrac{J}{ne}\\\Rightarrow v_d=\dfrac{6012520.07236}{8.46\times 10^{28}\times 1.6\times 10^{-19}}\\\Rightarrow v_d=0.000444187357592\ m/s$

Distance traveled

$s=v_dt\\\Rightarrow s=0.000444187357592\times 0.76\\\Rightarrow s=0.00033758239177\ m=0.33758239177\ mm$

The electron traveled 0.33758239177 mm