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JAMB Physics 1989 Question 43

Question 43

Current Electricity

An ammeter of resistance 0.1 Ω has a full-scale deflection of 50 mA. Determine the resultant full-scale deflection of the meter when a shunt of 0.0111 Ω is connected across its terminals.

  1. A.400 mA
  2. B.450 mA
  3. C.500 mA
  4. D.550 mA
Show the answer and explanation

Answer: C (500 mA)

Explanation

At full scale the p.d. is 0.1 × 0.05 = 0.005 V. The shunt carries 0.005/0.0111 ≈ 0.45 A, so the total is 0.05 + 0.45 = 0.5 A = 500 mA.