Alternating current has a voltage that cycles back and forth over time, so that

Question

Alternating current has a voltage that cycles back and forth over time, so that when using Ohm’s law, the effective voltage is used, called the “root mean square” (or RMS) voltage. In the United States, the household RMS voltage is 120 V, meaning the peak voltage is 120*21/2 = 170 V, and the voltage cycles back and forth over time between +170 V and -170 V. When using a dryer that uses 1875 W on average, what is the RMS current? What’s the peak current? The dryer makes heat by passing the current through resistive elements. What is the effective resistance of these elements?

Explanation / Answer

Avergae power = VRMS2 / R

1875= 120^2/R

R= 7.68 ohm

IRMS= 120/7.98 =15.03 A

Peak Current =15.03 * (2)^1/2=21.25 A

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