physics

posted by .

A small motor draws a current of 1.76 A from a 110 V line. The output power of the motor is 0.20 hp.
(a) At a rate of $0.060/kWh, what is the cost, in cents, of operating the motor for 4.0 h?
(b) What is the efficiency of the motor?

for (a) i am doing IV*hours*price and its coming up worng.
and for (b) i changed .2hp into Watts. and i got 149.2W.

im just not sure how to do this problem.

  • physics -

    Pin=VI=110 * 1.76=193.6W = 0.1936KW.

    a. C = $0.060/kwh * 0.1936kw * 4h =
    $0.0465 = 4.65 cents.

    b. Po = 0.2hp * 746W/hp = 149.2W.

    %Eff.=(Po/Pin)100%,
    %Eff.=(149.2/193.6)100% = 77.1

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Electricity

    A motor running at its rated power provides 2.6 lb-ft torque at its rated speed of 2020 rpm. The motor draws 5.6-A from a 230-V supply at a phase angle of 37 degrees. Determine the following: The horsepower delivered by the motor, …
  2. Physics

    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 …
  3. physics

    The electrical motor runs on a D.C source of emf E and internal resistance r. Show that power output of the motor is max where current drawn by the motor is E/2r.
  4. physics

    A 120-V motor has mechanical power output of 3.20 hp. It is 81.0% efficient in converting power that it takes in by electrical transmission into mechanical power. (a) Find the current in the motor. Answer: 24.6A (b) Find the energy …
  5. algebra

    The power (P) required to run a motor is equal to the voltage (E) applied to that motor times the current (I) supplied to the motor. If the motor data says the motor uses 180 watts of power and the voltage applied to the motor is 120 …
  6. PHYSICS 2 !!!

    At its normal operating speed, an electric fan motor draws only 10.9% of the current it draws when it just begins to turn the fan blade. The fan is plugged into a 120.0-V socket. What back emf does the motor generate at its normal …
  7. physics

    A 120-V motor has mechanical power output of 2.20 hp. It is 92.0% efficient in converting power that it takes in by electrical transmission into mechanical power. (a) Find the current in the motor (A) (b) Find the energy delivered …
  8. electrical engineering

    A three phase, four- pole, 30-hp, 220-V, 60-Hz, Y-connected induction motor draws a current of 77 A from the line source at a power factor of 0.88. At this operating condition, the motor losses are known to be the following: Stator …
  9. Physics

    Searches related to a motor lifts an elevator of mass m at constant speed. The power output of the motor is P and there are no frictional losses so that all the power output from the motor goes into lifting the elevator mass. What …
  10. Physics

    A motor lifts an elevator of mass m at constant speed. The power output of the motor is P and there are no frictional losses so that all the power output from the motor goes into lifting the elevator mass. What is the correct expression …

More Similar Questions