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JAMB Physics 1983 Question 24

Question 24

Current Electricity

In the circuit shown in Fig. 4, T is a resistor whose resistance falls as temperature increases. L1 and L2 are lamps. Assuming the cell has negligible internal resistance, as the temperature of T increases.

Diagram for this question
  1. A.L1 becomes brighter, L2 becomes dimmer
  2. B.L1 and L2 becomes brighter
  3. C.L1 becomes dimmer, L2 becomes brighter
  4. D.L1 becomes brighter, L2 does not change
  5. E.L2 becomes dimmer, L1 does not change.
Show the answer and explanation

Answer: D (L1 becomes brighter, L2 does not change)

Explanation

T is in series with L1, so as T's resistance falls more current flows and L1 brightens. L2 is directly across the cell, whose voltage is fixed, so it is unchanged.