Which one among the following statements related to electric cells is correct?
A.A primary cell is rechargeable.
B.A secondary cell can be used only once.
C.The emf of a battery is the power provided by the battery per unit current.✓ Correct
D.The unit of emf is Joule.
Explanation
Primary cells (e.g., dry cells) are not rechargeable, so (a) is wrong. Secondary cells (e.g., lead-acid, Li-ion) are rechargeable and can be used many times, so (b) is wrong. The SI unit of emf is the volt (joule per coulomb), not joule, so (d) is wrong. EMF can be defined as the energy supplied per unit charge, equivalent to power per unit current (since P = VI implies V = P/I). Hence option (c), defining emf as power per unit current, is correct.
💡 Practice unlimited CDS PYQs + AI-tracked progress on each topic. Sign up free →