voltage and diameter physics problem?
When the starter motor on a car is engaged, there is a 330 A current in the wires between the battery and the motor. Suppose the wires are made of copper and have a total length of 1.5 m
What minimum diameter can the wires have if the voltage drop along the wires is to be less than 0.40 V?
(answer should be in mm)
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The maximum resistance is 0.4V/330A = 1.212E-3 ohms
The resistivity of copper is 1.68E-8 OhmMeter, thus
1.212E-3 ohms = (1.68E-8 OhmMeter)(1.5m) / (Pi r^2)
r = 0.00257 meters = 2.57 mm radius, 5.15 mm diameter