Resistance of a light bulb question

AI Thread Summary
To determine the resistance of a light bulb using average power and voltage, the formula R = V²/P is applicable, where V is the RMS voltage. For a 75 W bulb connected to a 190 V source, the resistance can be calculated directly using this formula. The discussion highlights confusion around using frequency and whether to multiply by 2π, clarifying that for pure resistance, voltage and current are in phase. Additionally, the relationship between peak and RMS values is mentioned as relevant for understanding AC circuits. Overall, the focus is on correctly applying the power formulas for AC circuits to find resistance.
Pepsi24chevy
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Hey guys I am having some trouble with this simple questions:
What is the resistance of a light bulb that uses an average power of 75.0 W when connected to a 60.0 Hz power source having a maximum voltage of 190 V?


(b) What is the resistance of a 120 W bulb?

I tried doing it by (75/190)^2 * (2pi60) but this is not correct.
 
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One has to apply the equivalent of P = V I = V2/R = I2R for AC, so R = V2/P.

Since it is pure resistance, i.e. no reactance, the voltage and current are in phase.

Think of average and maximum.
 
Ok, do i still have to multiply the 60hz by 2pi? Also, how do i handle it being connected to the power source?
 
no but thanks for the link. I think that should of helped me get an idea
 
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