Question

The storage battery of a car has an emf of 12 V. If the internal resistance of the battery is 0.4 Ω, what is the maximum current that can be drawn from the battery?
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Answer 1

emf of car battery is 12V and internal and resistance of the battery is 0.4 ohm. so, the maximum current will be obtained when no external resistance is offered by with joining the two terminals. I mean, Rext 0 see daigram, according to Kirchoff's law, E - rI - RextI = 0 , here I is the maximum current passing through battery. I = E/(Rext + r) = 12/(0+ 0.4) = 30A hence maximum current = 30A

Answer 2

Answer:

Emf of car battery is 12V and internal and resistance of the battery is 0.4 ohm.

So, the maximum current will be obtained when no external resistance is offered by with joining of two terminals.

I mean,

$R _{ext} = 0$

See diagram,

according to kirchoff's law,

E - r × t - Rext × I = 0 ,

here I is maximum current passing through battery.

I = E/(Rest + r)

= 12/(0 + 0.4) = 30A

Hence maximum current = 30A