Chapter 7 QUIZ

ELECTRICAL POWER

1. Does an empty lamp socket have force?
2. Is any work done by an open circuit?
3. Is any power consumed by an open circuit?
4. A generator supplies a 72 ampere load at 600 volts. What is the power consumed by
    the load in watts? In kilowatts? In hp?
5. A 50 hp motor draws 80 amperes at 600 volts. What is the power input? Power output
    in watts? Efficiency?
6. The prime mover of a generator furnishes 37 hp to the generator. The electrical load on
    the generator is 70 amperes at 440 volts. What is the power input in watts? Power
    output in watts? Efficiency?

7. A power line has a drop of 18 volts in transmitting a load of 75 amperes. How much
    power is lost in this line?
8. What is the resistance of the line in problem 7?
9. If a line consumes 650 watts in transmitting 55 amperes, what is the potential drop?
10. How much power will be consumed by a 75 hp motor operating at 80 percent efficiency?
      In hp? In watts? In kilowatts?

Return to Chapter 7

Chapter 7 ANSWERS

ELECTRICAL POWER

1. Yes. There is an EMF present. It tries to force current across the open circuit but cannot.
2. No, as long as no current flows it is a case of force but no motion.
3. No. Again, force but no motion.
4.* 43,200 w.      43.2 kw.          57.9 hp.
5.  48,000 w.      37,300 w.      77.7 percent.
6.  27,602 w.      30,800 w.      89.6 percent.
7.  1,350 w.
8.  0.24 ohm.
9.  11.8 v.
10. 93.75 hp.       69,937.5       w. 69.94 w.
 

* The original manual gave this as an incorrect answer:    16,128 w.      16,128 kw.      2.16 hp.
    Thanks to Lou Nickles for finding the error.