Homework Solution

TP 4-13

Given:

    E_in = 25000 J

    E_out = 12000 J

    T_H = 600 K

    T_C = 300 K

Find:

    Would you be willing to back financially an inventor marketing the device?

Science:

e = (work output/ energy input ) x 100%

e_max = (1 - T_C /T_H) x 100%

where the temperatures must be expressed in kelvins

Solve:

e = (work output/ energy input ) x 100%

e = (12000 J)/(25000 J)) x 100%

e = 48.0%

e_max = (1 - T_C /T_H) x 100%

e_max = (1 - 300 K / 600 K) x 100%

e_max = 50.0%

    Since  e < e_max the device might work (does not violate the Second Law of Thermodynamics).