Three 70.0-W, 130-V lightbulbs are connected across a ? V = 130-V power source,

Question

Three 70.0-W, 130-V lightbulbs are connected across a ?V = 130-V power source, as shown in the figure below.  Find the total power delivered to the three bulbs and the potential difference across each. Assume the resistance of each bulb is constant (even though, in reality, the resistance increases markedly with current).

                ?VR1 =                                    V                              ?VR2 =                                    V                              ?VR3 =                                    V              Three 70.0-W, 130-V lightbulbs are connected across a ?V = 130-V power source, as shown in the figure below. Find the total power delivered to the three bulbs and the potential difference across each. Assume the resistance of each bulb is constant (even though, in reality, the resistance increases markedly with current). Find the total power delivered to the three bulbs. Find the potential difference across each bulb.

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 = 31.11111111111111 W

Power dissipated in R2 and R3 = (potential across R2)^2 / R2 = P/9 =7.777777777777778 W

VR1 = 2V/3 = 86.66666666666667 V ,

VR2 = VR3 =43.3295652173913 V

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