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JAMB Physics 1999 Question 41

Question 41

Current Electricity

A galvanometer has a resistance of 5 Ω. By using a shunt wire of resistance 0.05 Ω, the galvanometer could be converted to an ammeter capable of reading 2 A. What is the current through the galvanometer?

  1. A.2 mA
  2. B.10 mA
  3. C.20 mA
  4. D.25 mA
Show the answer and explanation

Answer: C (20 mA)

Explanation

The galvanometer and shunt share the same p.d.: I × 5 = 0.05 × (2 − I), so I = 0.1/5.05 ≈ 0.020 A = 20 mA.