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JAMB Physics 2020 Question 8

Question 8

Current Electricity

The effect of closing the key K in the circuit shown in Fig. 1 would be to

Diagram for this question
  1. A.increase the current by 0.4A.
  2. B.reduce the current by 0.4A
  3. C.increase the current by 0.6A.
  4. D.reduce the current by 0.6A.
Show the answer and explanation

Answer: A (increase the current by 0.4A.)

Explanation

With K open: R = 8 + 2 = 10 Ω, I = 6 ÷ 10 = 0.6 A. With K closed the two 8 Ω resistors are in parallel (4 Ω): R = 6 Ω, I = 1 A. The current rises by 0.4 A.