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Q18 (CDS-I/2026) Science & Technology › Basic Science (Physics, Chemistry, Biology)

Which one among the following statements related to electric cells is correct ?

Result
Your answer: —  Â·  Correct: C

Explanation

The correct statement is Option C. Electromotive force (emf) is defined as the energy supplied by a source (like an electric cell) per unit charge. Mathematically, emf (ε) = Work (W) / Charge (Q). Since Power (P) = W/t and Current (I) = Q/t, then P/I = (W/t) / (Q/t) = W/Q = ε. Therefore, emf is the power provided by the battery per unit current.

  • Option A: Incorrect. Primary cells are designed for single use and are non-rechargeable.
  • Option B: Incorrect. Secondary cells (like Lead-acid or Lithium-ion) are rechargeable and can be used many times.
  • Option D: Incorrect. The SI unit of emf is the Volt (V), which is equivalent to Joule per Coulomb (J/C). Joule is the unit of energy, not emf.
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