Concept:The brightness of a lamp depends on the electric power it dissipates.
Explanation:For a lamp of fixed resistance
R, the power is
P=RV2.
So the greater the voltage across the lamp, the brighter it glows.
When two cells are connected in series, their e.m.f.s add up to give
2E.
When the two lamps are connected in parallel, each lamp receives the full voltage
2E.
This gives a larger current and greater power in each lamp than in the other arrangements.
Therefore, the lamps are brightest when the two cells are in series and the two lamps are in parallel.
Answer:The lamps are brightest in the circuit with the cells in series and the lamps in parallel.
Correct option: B. Q.
