Homework Help Forum: Physics

Posted by Jessi on Sunday, October 18, 2009 at 6:03pm.

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 - bobpursley, Sunday, October 18, 2009 at 6:17pm

  electricalpower*.82=mechanicalpower electrical power= 2hp(746watts/hp)/.82 IV= 2*746/.82 I= 2*746/(.82*120) I get about 15 amps

  
  

• Physics - Jessi, Sunday, October 18, 2009 at 6:26pm

  thanks! i was multiplying by 0.82 instead of dividing

  
  

Answer this Question

First Name:
School Subject:
Answer: