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.

A) Find the total power delivered to the three bulbs.

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

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

D) 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

R of each bulb = V*V/P

According to the arrangement,

Potential drop across R1 = 2V/3 ; Potential drop across R2 and R3 = V/3

Power dessipated in R1 = (potential across R1)^2 / R1 = 4P/9 = 17.778 W

Power dissipated in R2 and R3 = (potential across R2)^2 / R2 = P/9 =4.45 W

VR1 = 2V/3 = 66.66666666666667 V , VR2 = VR3 = 33.33333333333333 V

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