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A 120-V motor has mechanical power output of 2.00 hp. It is 82.0% efficient in converting power that it takes in by electrical transmission into mechanical power.
(a) Find the current in the motor
(b) Find the energy delivered to the motor by electrical transmission in 3.30 h of operation
(c) If the electric company charges $0.160/kWh, what does it cost to run the motor for 3.30 h?

Ok so I started the problem by manipulating the power equation (P=IV) to get I=P/V and I got 10.2 A but it says that that's not correct. I assume the other parts aren't correct because I don't have part (a) right. What am I doing wrong. The power I used was 1.22kW

  • Physics -


    electrical power= 2hp(746watts/hp)/.82

    IV= 2*746/.82
    I= 2*746/(.82*120)
    I get about 15 amps

  • Physics -

    thanks! i was multiplying by 0.82 instead of dividing

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