In doing a load of clothes, a clothes drier uses 18 A of current at 240 V for 33 min. A personal computer, in contrast, uses 2.7 A of current at 120 V. With the energy used by the clothes drier, how long (in hours) could you use this computer to "surf" the internet?
2007-03-07 11:55:22 · 1 answers · asked by madison c 1 in Science & Mathematics ➔ Physics
Watt-hrs used by the dryer:
Power = E*I = 240 V*18 A = 4320 Watts
Watt-hrs = 4320 Watts*(33/60) hrs = 2376 Watt-hrs
Time for the PC to use that many Watt-hrs
Power = E*I = 120 V*2.7 A = 324 Watts
2376 Watt-hrs = 324 Watts*t
t = 7 1/3 hrs
Note: This is an approximation. The dryer power is mostly running the heater element (which is resistive) but not totally. The motor also consumes power and that's more complicated because of reactance. The PC also has reactance probably more of a factor than for the dryer. So these numbers are approximations. Error could be 20-30%.
2007-03-07 12:29:31 · answer #1 · answered by sojsail 7 · 1⤊ 0⤋