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Question:

jharry23
jharry23
Student
College - Junior

A commonly used unit is the kilowatt hour. The physical quantity measured in kilowatt hour is

Multiple Choice:

A. current

B. work (energy)

C. force

D. power

E. None of these

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Posted by jharry23 on Monday November 9, 2009 at 7:20 AM and tagged with energies, math.

Answers:

  1. neela
    neela Teacher
    Graduate School

    eNotes Editor

    The energy is measured in watt second, which is equal to a joule.

    Both watt second or joules are the standard scientific unit of energy. Therefore, one kilowatt hour =( 1000 watt )(3600 seconds) =3.6*10^6 watt seconds of energy.

    Normally we use kilowatt hour units as commercial the energy unit which is also written like 1Kwh and is equal to 3.6*10^6 watt second units of energy. Choose the option B.

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    Posted by neela on Monday November 9, 2009 at 7:35 AM

  2. subbundd
    subbundd Teacher
    High School - 12th Grade

    I will answer with mathematical analysis:Work done(W) = Force x distance (Units N-mt or Kg-mt) = = F*x

    The rate of doing work is called Power.Mathematically the derivative of Work done is Power.ie dW/dt = d(F*x)/dt = F*v

    Units = N-m/sec = 1 watt.THe capacity of doing work is called Emergy.hence it is time dependent. Physically Work done and energy are same.dW=P*dt

    Emergy =Powerxtime =watt-sec or biger unit KWh. Therefore Answer is B.

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    Posted by subbundd on Tuesday November 10, 2009 at 6:34 AM