A Lamp and a Coffee Maker Connected in Parallel
Resistance of the lamp (r) = 156.52 ohm (Approx.)
Calculation of Resistance of the Lamp
Given:
Total power p = 140 W
Resistance of the coffee maker = 300 Ohm
Voltage v = 120 V
Find:
Resistance of the lamp (r)
Computation:
We know that
p = v² / R
So,
Total power p = [Voltage² / Resistance of the lamp (r)] + [Voltage² / Resistance of the coffee maker]
140 = [120² / r] + [120² / 300]
140 = 120² [1/r + 1/300]
Resistance of the lamp (r) = 156.52 ohm (Approx.)