Home › ISC Class 12 › Physics › Current Electricity › A car storage battery has emf 12 V and internal …
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_
Related questions
For a battery of emf ε and internal resistance r driving current I through external resistA galvanometer of resistance G is converted into a voltmeter reading full-scale voltage V A galvanometer of resistance G shows full-scale deflection at current I_g. To convert it iThe relation between current density j, drift velocity v_d, number density n and charge e A wire has a resistance R. It is stretched uniformly so that its length becomes 2L. The neKirchhoff current law at a junction is a statement ofTwo cells of emf ε and internal resistance r each are connected in parallel. The equivalenA potentiometer of length L is used to compare emfs. If the balance lengths for cells of e