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

Question

Quizplus · Accepted Answer

We can use Ohm's Law to solve for the resistance of the motor. 
First, we need to find the voltage across the motor, which is equal to the battery voltage minus the voltage drop across the internal resistance of the battery:

V = 12.0 V - (100 A)(0.080 Ω) 
V = 4.0 V

Now we can use Ohm's Law:

V = IR

Solving for R:

R = V / I 
R = 4.0 V / 100 A 
R = 0.040 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 Ω\OmegaΩ

A 120 V Battery Has an Internal Resistance of 0 $\Omega$