Three 40.0-W, 100-V lightbulbs are connected across a 100-V power source, as sho

Question

Three 40.0-W, 100-V lightbulbs are connected across a 100-V power source, as shown in Figure. Find the total power delivered to the three bulbs.

Find the potential difference across R1. Assume the resistance of each bulb is constant (even though, in reality, the resistance increases markedly with current).

Find the potential difference across R2. Assume the resistance of each bulb is constant (even though, in reality, the resistance increases markedly with current).

Find the potential difference across R3. Assume the resistance of each bulb is constant (even though, in reality, the resistance increases markedly with current).

Explanation / Answer

the power delivered to the three bulbs is

P = 40 + 40 + 40 = 120 W

the total current in the circuit is

P = V x I

or I = (P/V)

where V = 100 V

as the resistors R1,R2 and R3 are in series therefore the same current flows through the three resistors therefore

V1 = I x R1,

V2 = I x R2

and V3 = I x R3

where V1,V2 and V3 are potential differences across the resistors

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