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JAMB Physics 2005 Question 23

Question 23

Electrostatics

If the distance between two point charges is increased by a factor of four, the magnitude of the electrostatic force between them will be

  1. A.½ of its former value.
  2. B.1/16 of its former value.
  3. C.1/4 of its former value.
  4. D.4 times its former value.
Show the answer and explanation

Answer: B (1/16 of its former value.)

Explanation

Coulomb's law: F ∝ 1/r2, so making r four times bigger makes F (1/4)2 = 1/16 of its former value.