In the figure below, the voltage source is 120 V, the wire resistance is 0.400 ?
ID: 2272157 • Letter: I
Question
In the figure below, the voltage source is 120 V, the wire resistance is 0.400 ?, and the bulb is nominally 59.3 W. When the motor (which has a low resistance) comes on, a large current flows causing a significant voltage drop in the wire. This reduces the voltage received by the bulb and causes it to dim noticeably.
(a) What power will the bulb dissipate if a total of 27.3 A passes through the wires when the motor comes on? Assume negligible change in bulb resistance.
In the figure below, the voltage source is 120 V, the wire resistance is 0.400 ?, and the bulb is nominally 59.3 W. When the motor (which has a low resistance) comes on, a large current flows causing a significant voltage drop in the wire. This reduces the voltage received by the bulb and causes it to dim noticeably.Explanation / Answer
R bulb = 120^2/59.3 = 242.8 ohms
now
Req = V/ I = 120 /27.3 = 4.4 ohms
Req - 0.4 = Rp = 4 ohms
so V accross bulb = 120 - 27.3*0.4 = 109.08 V
so Power = V^2/R = 109.08^2/242.8 = 49 W