Question

A 12 volt battery in a motor vehicle is capable of supplying the starter motor with 150 A. It is noticed that the terminal voltage of the battery drops to 10 V when the engine is cranked over with the starter motor. Determine the internal resistance of the 12 volt battery.

Answer 1

Answer:

$r=\frac{1}{75}$ Ω≈0.01333Ω

Explanation:

You can check the internal resistance model in the image I attached you.

Now using Kirchhoff's voltage law:

ε=$Ir+IR$  (1)

Where:

$IR=V_R=LoadVoltage=10V$

ε=12V

$I=150A$

Evaluating the data provide in (1)

$r=\frac{12-10}{150} =\frac{1}{75}$≈0.01333Ω