Refer to Figure 20.7 and the discussion of lights dimming when a heavy appliance

Question

Refer to Figure 20.7 and the discussion of lights dimming when a heavy appliance comes on.

Refer to Figure 20.7 and the discussion of lights dimming when a heavy appliance comes on. ohm , and the bulb is nominally 70.0 W, what power will the bulb dissipate if a total of 32.0 A passes through the wires when the motor comes on? Assume negligible change in bulb resistance. W (b) What power is consumed by the motor? kW Figure 20.7 (a) Given the voltage source is 120 V, the wire resistance R1 is 0.400

Explanation / Answer

Voltage across R2 and R3 is 120 - (0.40 x 32) = 107.2 V

now for 120 volts,the bulb is rated 70 W.

as power is directly proportional to square of voltage,

70/P=120^2/107.2^2

P= 55.86 W

b) Total power supplies by Source = VI = 120 x 32 = 3840 W

Consumed by wire = i^2 R = 0.4 x 32^2   =409.6 W

Cosumed by bulb = 55.86 W

by motor = 3840 - 409.6 - 55.86 = 3374 Watt = 3.374 kW

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