Question:
The storage battery of a car has an emf of 12 V. If the internal resistance of the battery is 0.4Ω, what is the maximum current that can be drawn from the battery?
Solution:
Emf of the battery, E = 12 V
Internal resistance of the battery, r = 0.4 Ω
Maximum current drawn from the battery = I
According to Ohm’s law,
$E=I r$
$I=\frac{E}{r}$
$=\frac{12}{0.4}=30 \mathrm{~A}$
The maximum current drawn from the given battery is 30 A.