Homework Solution

TQ 3-6

Given:

    The overall efficiency is 29% for conversion of the chemical energy of coal to work done by an electric motor.

    The efficiency for production of electricity by coal at the power plant is 35%.

    The efficiency for transmission of electrical energy from the power plant to the motor is 85%.

Find:

    efficiency of the electric motor

Science:

    e_total =  e_prod  e_trans e_motor

Solve:

    e_{motor =}  e_total / (e_prod  e_trans )

    e_{motor = (0.29)/[(0.35)(0.85)] = 0.9748}

    _{Efficiency of motor is 97%}