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JAMB Physics 2006 Question 29

Question 29

Capacitors

If the capacitance of a capacitor is C = εA/d, which of the following parameters is varied when a variable capacitor is used for tuning radio sets?

  1. A.Area and distance
  2. B.Constant (ε) only.
  3. C.Constant (ε) and area.
  4. D.Distance only.
Show the answer and explanation

Answer: A (Area and distance)

Explanation

In a tuning capacitor, turning the knob moves one set of plates between the other, changing the overlapping area of the plates (and so the capacitance); the dielectric (air) stays the same.