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JAMB Physics 1988 Question 45

Question 45

Alternating Current Circuits

Which of the following ammeters may be used to measure alternating currents? I. Moving-coil ammeter II. Moving-iron ammeter III. Hot-wire ammeter

  1. A.I and II only
  2. B.II and III only
  3. C.I and III only
  4. D.I, II and III.
Show the answer and explanation

Answer: B (II and III only)

Explanation

Moving-iron and hot-wire meters respond the same way whichever way the current flows. A moving-coil meter's pointer reverses with the current, so it only measures d.c.