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JAMB Physics 2010 Question 41

Question 41

Current Electricity

A galvanometer with full-scale deflection of 10 mA is to be converted to a voltmeter with full-scale deflection of 5 V. If a series resistance of 498Ω is used for the conversion, the resistance of the galvanometer is

  1. A.2 Ω.
  2. B.10 Ω.
  3. C.5 Ω.
  4. D.1 Ω.
Show the answer and explanation

Answer: A (2 Ω.)

Explanation

At full scale V = I(Rg + R): 5 = 0.01 × (Rg + 498), so Rg + 498 = 500 and Rg = 2 Ω.