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JAMB Physics 1980 Question 28

Question 28

Current Electricity

A milliammeter of resistance 5 Ω and full scale deflection of 50 mA is to be used to measure a potential difference of 50 V. The resistance of the multiplier should be

  1. A.95 Ω
  2. B.110 Ω
  3. C.595 Ω
  4. D.995 Ω
  5. E.1005 Ω.
Show the answer and explanation

Answer: D (995 Ω)

Explanation

At full scale, 50 V must drive 0.05 A through the meter plus the multiplier: 50 = 0.05 × (5 + R), so 5 + R = 1000 and R = 995 Ω.