Question

a light bulb will glow when electrons flow through it. as the electron flow increases, the brightness increases as well. a student hooks up two circuits containing three light bulbs in each circuit. in one circuit the lights are connected in series and in the other circuit the lights are hooked up in parallel. if you could only see the lights in the circuit and the wires were covered from view, how could you determine the type of circuit the lights are arranged in? a if all the lights are equal brightness, it is a series circuit. b if you add another bulb and it gets dimmer, it is a parallel circuit. c unscrew one light, if the others remain on it is a series circuit. d unscrew one light, if the others remain on it is a parallel circuit.

Explanation:

• For option A: Identical bulbs in series have equal brightness, but identical bulbs in parallel also have equal brightness (since they share the same voltage), so this test doesn't work.
• For option B: Adding a bulb to a parallel circuit keeps voltage the same for existing bulbs, so their brightness doesn't dim; dimming happens in series when total resistance increases, lowering current.
• For option C: In a series circuit, unscrewing one bulb breaks the single path for current, so all bulbs go out.
• For option D: In a parallel circuit, each bulb has its own separate current path. Unscrewing one bulb only breaks its path, leaving the others connected to the power source, so they stay on.

Answer:

D. Unscrew one light, if the others remain on it is a parallel circuit.