A three-way lightbulb has two filaments with resistances R1 and R2 connected in

Question

A three-way lightbulb has two filaments with resistances R1 and R2 connected in series. The resistors are connected to three terminals, as indicated in the figure (Figure 1) , and the light switch determines which two of the three terminals are connected to a potential difference of 120 V at any given time. When terminals A and B are connected to 120 V the bulb uses 80W of power. When terminals A and C are connected to 120 V the bulb uses 45W of power.

Part B

What is the resistance R2?

Express your answer using two significant figures.

Part C

How much power does the bulb use when 120 V is connected to terminals B and C?

Express your answer using two significant figures.

A three-way lightbulb has two filaments with resistances R1 and R2 connected in series. The resistors are connected to three terminals, as indicated in the figure (Figure 1) , and the light switch determines which two of the three terminals are connected to a potential difference of 120 V at any given time. When terminals A and B are connected to 120 V the bulb uses 80W of power. When terminals A and C are connected to 120 V the bulb uses 45W of power. Part B What is the resistance R2? Express your answer using two significant figures. Part C How much power does the bulb use when 120 V is connected to terminals B and C? Express your answer using two significant figures.

Explanation / Answer

Using Power = Voltage^2 / Resistance

a) R1 = 120^2 / 80 = 180 ohms

b) (R1 + R2) = 120^2 / 45 = 320 ohms, so R2 = 140.0 ohms

c) P = 120^2 / 140 = 102.86 watts

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