Units 8 and 9 Review

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1. Which of the following are true of static charges? (Circle all that are true.)

  1. Like charges repel.
  2. Like charges attract.
  3. Opposite charges repel.
  4. Opposite charges attract.
  5. A positively charged object has lost electrons.
  6. A positively charged object has gained protons.
  7. A negatively charged object has lost protons.
  8. A negatively charged object has gained electrons.

 

2. The charge of one electron is -1.6 X 10-19 Coulombs. If a neutral object loses 1.5x106 electrons, then what will be its charge?

3. A negatively-charged balloon is held above (without touching) a neutral electroscope. The presence of the nearby balloon causes the needle of the electroscope to deflect.

Draw the charges on "induced" or "polarized" neutral electroscope below. Explain how the balloon has induced the temporary charge upon the electroscope.

 

Consider the negatively charged electroscope at the right for review questions #4 and #5.

4. If a negatively charged balloon is brought near the top of the electroscope, the deflected straw will:

  1. not move at all.
  2. be deflected more.
  3. be deflected less.

 

 

5. If a positively charged balloon is brought near the top of the electroscope, the deflected straw will:

  1. not move at all.
  2. be deflected more.
  3. be deflected less.

 

 

6. The outer electrons in metals are not tightly bound to the atomic nuclei. They are free to roam in the material. These materials are good

  1. conductors.
  2. insulators.
  3. for nothing.

 

For questions #7 and #8, consider the following situation. Connor Duct (Con to his friends) takes a positively charged metal tube and touches a metal sphere on an insulated stand as shown below. Draw the direction of electron flow.

7. Electrons will flow until the two objects have equal ____.

  1. charge.
  2. electric potential.
  3. potential energies.

 

 

8. The charge on the metal sphere will end up ___.

  1. neutral
  2. negative
  3. positive

 

 

9. If an electroscope, charged up with excess negative charge, is touched and grounded, then it will end up with ___ charge.

  1. neutral
  2. negative
  3. positive

 

 

10. What will be the charge of the following sphere in step e if steps a - d are followed?

Explain how the object acquires this charge.

 

 

11. Charge carriers in a metal are electrons rather than protons because electrons are __________.

  1. loosely bound
  2. lighter
  3. far from a nucleus
  4. all of the above
  5. none of the above

 

12. Two like charges ________.

  1. attract each other
  2. repel each other
  3. neutralize each other
  4. have no effect on each other
  5. must be neutrons

 

13. When the distance between two charges is halved, the electrical force between the charges _____.

  1. quadruples
  2. doubles
  3. is reduced by 1/4
  4. halves
  5. none of these

 

14. If you comb your hair and the comb becomes positively charged, then your hair becomes _______.

  1. positively charged
  2. negatively charged
  3. uncharged

 

15. A negatively charged rod is brought near a metal can that rests on a wood table. You touch the opposite side of the can momentarily with your finger. The can is then _______.

  1. positively charged
  2. negatively charged
  3. uncharged
  4. charged the same as it was

 

16. Two charges have a force of -55 Newtons. The force is ___.

  1. attractive
  2. repulsive
  3. either attractive or repulsive

 

17. A charge feels a force of 0.50 Newtons when it is 1 meter away from a Van de Graff Generator. The force will be ___ Newtons when the charge is moved 2 meters.

  1. 0.125
  2. 0.25
  3. 0.50
  4. 1.00
  5. 2.00

 

18. Two charges are 0.40 meters apart. One charge is 1.0 X 10-10 Coulombs. The other is 3.0 x 10-9 Coulombs. The force between these two charges is ___ Newtons.

  1. 1.69 X 10-8
  2. 6.75 X 10-9
  3. 0.050
  4. 1.5 X 10-7

 

19. If the both of the above charges are doubled, while the distance is doubled, by what factor will the force change?

  1. 1
  2. 2
  3. 4
  4. 1/2
  5. 1/4

 

20. Two charges separated by one meter exert a one N force on each other. If the charges are pushed to 1/4 meter separation, the force on each charge will be _________.

  1. 1 N
  2. 2 N
  3. 4 N
  4. 8 N
  5. 16 N

 

21. Two charges separated by one meter exert a one N force on each other. If the charges are pulled to 3 m separation distance, the force on each charge will be ________.

  1. 0.33 N
  2. 0.11 N
  3. 0 N
  4. 3 N
  5. 9 N

 

22. A charge of 0.30 Coulombs has a potential energy of 400 Joules has an electric potential (i.e., voltage) of ___ Volts.

  1. 1300
  2. 400
  3. 120
  4. 0.0075

 

23. If a Van de Graff Generator has an electric potential (i.e., a voltage) of 600 Volts and a charge of 0.000001 Coulombs. What is the PE of the charge?

  1. 6.0 X 108 J
  2. 600 J
  3. 6 X 10-4 J

 

24. If you were to grab onto a single wire (suspended above the ground by the wire only) that was at a potential of 1000 Volts,

  1. You should make sure that you are insured.
  2. You would not have any current flow since there is no electric potential difference.
  3. There will be a current, but your resistance is so large that you will not be electrocuted.

 

25. In the water analogy, current is like

  1. water flow.
  2. water pressure.

 

26. In an electrical circuit, electrons come from _____________.

  1. a dry cell, wet cell or battery
  2. the back emf of motors
  3. the power station generator
  4. the electrical conductor itself
  5. none of these

 

27. The source of electrons lighting an incandescent light bulb is ________.

  1. the power company
  2. electrical outlet
  3. atoms in the light bulb filament
  4. the wire leading to the lamp
  5. the source voltage

 

28. In a common circuit, electrons move at speeds of ____________.

  1. a fraction of a centimeter per second
  2. many centimeters per second
  3. the speed of a sound wave
  4. the speed of light
  5. none of these

 

29. The number of electrons delivered to an average American home by an average power utility in 1984 was ______________

  1. zero
  2. 110
  3. 220
  4. billions of billions
  5. none of these

 

30. Two lamps, one with a thick filament and one with a thin filament, are connected in series. The current is greater in the lamp with the ____________.

  1. thick filament
  2. thin filament
  3. the same in each lamp

 

31. Two lamps, one with a thick filament and one with a thin filament, are connected in parallel to a battery. The voltage in greatest across the lamp with the _____________.

  1. thick filament
  2. thin filament
  3. both voltages are the same

 

32. Two lamps, one with a thick filament and one with a thin filament, are connected in parallel to a battery. The current is largest in the lamp with the _____________.

  1. thick filament
  2. thin filament
  3. current is the same in both

 

33. Two lamps, one with a thick filament and one with a thin filament are connected in series to a battery. The voltage is greater across the lamp with the ____________.

  1. thick filament
  2. thin filament
  3. voltage is the same for both

 

34. As more lamps are put into a series circuit, the overall current in the circuit _____________.

  1. increases
  2. decreases
  3. stays the same

 

35. As more lamps are put into a parallel circuit, the overall current in the circuit ____________.

  1. increases
  2. decreases
  3. stays the same

 

36. A 60 W light bulb and a 100 W light bulb are each rated at 120 V. Which light bulb has a larger resistance?

  1. the 60 W bulb
  2. the 100 W bulb
  3. both have the same resistance

 

37. A heater uses 20 A when used in a 110 V line. If electric power costs 10 cents per kilowatt hour, the cost of running the heater for 10 hours is ___________.

  1. $0.22
  2. $0.55
  3. $2.20
  4. $5.50
  5. none of these

 

Consider the following light bulb for questions #38 and #39. A light bulb has 144-ohm when it is placed across a 120 V potential difference.

38. The current going through the light bulb is ___ Amps.

  1. 1.0
  2. 0.83
  3. 1.2
  4. 4.0

 

39. The power rating of the bulb is ___ Watts.

  1. 40
  2. 60
  3. 80
  4. 100

 

40. A circuit has a current of 2.0 Amps. How many Coulombs of charge pass through the circuit in 3.0 seconds?

  1. 2.0 C
  2. 3.0 C
  3. 4.0 C
  4. 6.0 C

 

41. Find the voltage, current, and resistance where it is needed below.

 

 

 

 

 

 


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This page last updated on March 3, 1998.