CDS 2026 (I) General Knowledge, question 18

Topic: Physics

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Q18

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

  1. (a) A primary cell is rechargeable.
  2. (b) A secondary cell can be used only once.
  3. (c) The emf of a battery is the power provided by the battery per unit current.Correct answer
  4. (d) The unit of emf is Joule.

Solution.

Answer: (c) The emf of a battery is the power provided by the battery per unit current.

  1. Emf is the energy supplied by a cell per unit charge.
  2. Dividing the power supplied by the source by current gives the same quantity.
  3. Primary cells are ordinarily non-rechargeable, secondary cells are rechargeable, and the emf unit is the volt, or joule per coulomb.