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JAMB Physics 1998 Question 46

Question 46

Electromagnetic Induction

A transformer which can produce 8 V from a 240 V a.c. supply, has an efficiency of 80%. If the current in the secondary coil is 15 A, calculate the current in the primary coil.

  1. A.0.625 A
  2. B.1.600 A
  3. C.2.500 A
  4. D.6.250 A
Show the answer and explanation

Answer: A (0.625 A)

Explanation

Output power = 8 × 15 = 120 W. Input power = 120 ÷ 0.8 = 150 W, so the primary current = 150 ÷ 240 = 0.625 A.