888 The voltage supplied by a wall socket varies with time, reserving its polari

Question

888 The voltage supplied by a wall socket varies with time, reserving its polarity with a constant frequency, as shown in the graph. What is the rms value Vrms of the voltage plotted in the graph? When a lamp is connected to a wall plug, the resulting circuit can be represented by a simplified AC circuit, as shown in the figure. Here the lamp has been replaced by a resistor with an equivalent resistance R = 120 ohm. What is the rms value Irms of the current flowing through the circuit? What is the average power Pavg dissipated in the resistor?

Explanation / Answer

in the graph it was clear that maximum voltage is vmax = 170 V

each unit on the y-axis represents 20 V

A) rms voltage Vrms = Vmax/Sqrt(2) = 170/1.414 = 120.2 V

b) rms current Irms = Vrms/R = 120.2/120 = 1.00173 A

C) Pavg = Irms^2*R = 1.00173^2*120 = 120.416 W

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