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 120V at any given time. When terminals A and B are connectedto 120V the bulb uses 80 W of power. WhenterminalsAand Care connected to 120Vthe bulb uses 40 W of power.

What is the resistance R2?_________(ohms)

How much power does the bulb use when 120V is connected to terminalsBand C? ____________=W

Explanation / Answer

Using Power = Voltage^2 / Resistance a) R1 = 120^2 / 80 = 189.5 ohms b) (R1 + R2) = 120^2 / 40 c) P = 120^2 / 108 = 133.3 watts

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