You and a friend are studying late t night. There are three 180 W light bulbs an
ID: 1654145 • Letter: Y
Question
You and a friend are studying late t night. There are three 180 W light bulbs and a radio with an internal resistance of 55.0 Ohm plugged into the living room electrical outlets. You decide to have a break and have a snack, turning on the pop corn machine that draws 9.00 A. How much electrical power are you using? Data: Assume the electric company provide you with 110 V potential difference. All the electrical outlets are part of the same 110-V circuit which has a 10-A circuit breaker. How much current in amperes (A) is required to feed all the devices described above? This tells you if you should or should not turn on the pop-corn machine. You are so tired after studying that you leave all of these household devices turned on for 12.0 hours. Calculate the cost (in dollars) of the electric bill the commercial rate is $ /kWh? (Do not enter units)Explanation / Answer
resistance of bulb = V^2 / P = 110^2 / 180
R = 67.2 ohm
current drawn by each bulb = 110 / 67.2 = 1.64 A
current drawn by radio = 110 / 55 = 2 A
total current drawn = 9 + 2 + 3(1.64) = 15.9 A
Power consupmtion = V I = 15.9 x 110
= 1750 Watt
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current used in above scenerio = 15.9 A
should not turn on the machine
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current = 2 + 3(1.64) = 6.9 A
Power = V I = 110 x 6.9 = 759 W = 0.759 kW
energy used = 0.759 x 12 = 9.11 kWh
cost = 0.09 x 9.11 = 0.82 dollars
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