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A car storage battery has emf 12 V and internal resistance 0.4 $\Omega$. The maximum current that can be drawn from it (short-circuit current) is
A4.8 A
B12 A
C48 A
D30 A
Answer & Solution
Correct answer: D. 30 A
1. Maximum current is drawn when the external resistance is zero ($R = 0$).
2. Then $I_{max} = \varepsilon/r$.
3. $I_{max} = 12/0.4 = 30\ \text{A}$.
4. 4.8 A multiplies instead of divides; 48 A misplaces a decimal.
_Source: NCERT Class 12 Physics Ch 3 "Current Electricity", p.14_
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