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JAMB Physics 1991 Question 37

Question 37

Current Electricity

A moving coil galvanometer of 300 Ω resistance gives full scale deflection for 1.0 mA. The resistance, R, of the shunt that is required to convert the galvanometer into a 3.0 A ammeter is

  1. A.899.70 Ω
  2. B.10.00 Ω
  3. C.0.10 Ω
  4. D.0.01 Ω
Show the answer and explanation

Answer: C (0.10 Ω)

Explanation

The shunt carries 3 − 0.001 = 2.999 A at the meter's p.d. of 300 × 0.001 = 0.3 V. R = 0.3/2.999 ≈ 0.10 Ω.