posted by Anonymous .
a 12V , 3A motor takes 120 minutes to do a certain job. a 120V, 8A motor takes 5 minutes to do the same job. Which motor uses the least energy and by how much?
where energy is in Joules.
Power of the motor P = 3.8hp
Motor is 90% efficient.
Therefore Power absorbed by the motor is (2834.8W)/(0.9) =3150W
But power P = V I
then current in the motor I =(3150W)/(120V)
Energy delivered to the motor E = P*t
= 4.536 *107J
(c) E = (3150W)(4h)
Therefore cost to run the motor for 4h is(12.6kWh)($0.16/kWh)