A 12.0 V battery has an internal resistance of 0.080 Ω. If the battery supplies 100 A when connected to a starter motor, what is the resistance of the motor?
A) 0.080 Ω
B) 0.20 Ω
C) 0.0012 Ω
D) 0.040 Ω
E) 0.012 Ω

Question

Quizplus · Accepted Answer

We can use Ohm's Law to solve for the resistance of the motor.

First, we need to find the total resistance of the circuit:

Rtotal = Rinternal + Rmotor

Now we can use Ohm's Law:

V = IR
12.0 V = 100 A * Rtotal
Rtotal = 0.12 Ω

Substituting in the given internal resistance:

Rinternal + Rmotor = 0.12 Ω
0.080 Ω + Rmotor = 0.12 Ω
Rmotor = 0.04 Ω

Therefore, the resistance of the motor is 0.040 Ω, which is answer choice D.

A 120 V Battery Has an Internal Resistance of 0