Humberto builds two circuits using identical components.Circuit 1: A series circuit with three lightbulbs Circuit 2: A parallel circuit with three lightbulbsHe then adds two more lightbulbs in a series with the bulbs in circuit 1 and two more lightbulbs on new branches in parallel with each bulb in circuit 2.

Adding two bulbs in series increases the total resistance of circuit 1. With the same power source, that reduces the current, so the original bulbs and the added bulbs all shine more dimly. In circuit 2, the bulbs are connected in parallel, so each branch still gets the same voltage as before; adding branches does not change the original bulbs’ brightness. Thus, choice B is correct.

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