Download ectrostatics Review KEY 1/19

TEACHER ANSWER KEY
Electrostatics Test Study Guide
1.
The study of electric charge that can be collected and held in one place is called Electrostatics.
2. Identify the SI units for the following:
Measurement
Electric Field
Strength (E)
Electric force
SI Unit
Newton/coulomb (N/C)
Newtons (N)
Measurement
Potential Difference
(voltage)
Charge
SI Unit
Volts (V)
Coulomb (C)
3. What is the charge of an electron? negative
4. When two objects have the same charge, they will ( attract, repel ).
5. When two objects have different charges, they will ( attract, repel ).
6. What charge will you hair have if you rub a balloon on your head and the balloon becomes
negatively charged? positive
7. One coulomb of negative charge has how many electrons? 6.24 x 1018
8. The charge on an electron is equal to the charge on a proton.
9. A rod carrying a negative charge is brought near sphere A. If sphere B is
then separated from sphere A, what charge will be on sphere B? Negative
10. Balloons attract electrons. You rub your hair with the balloon. The
balloon becomes negative and your hair becomes positive.
11. If you bring a negatively charged balloon near an electroscope, the leaves of the electroscope
receive a negative charge because of induction.
12. If you have a strong electrical force, the magnitude of the charge is ( small, large ).
13. Which is the example of conduction?
A) Rubbing a balloon on your arm
B) Walking across a carpeted floor
C) Making your hair stand up when you are touching the van de Graaf generator.
D) Moving a soda can with a negatively charged rod.
14. If you have equal numbers of protons and electrons your object has a __ charge.
A) Positive
B) Negative
C) Neutral
15. If you have more protons than electrons, your object will have a _____ charge.
A) Positive
B) Negative
C) Neutral
16. If you have more electrons than protons, your object will have a _____ charge.
A) Positive
B) Negative
C) Neutral
17. In a good insulator, electrons
A) do not exist.
B) are free to move around.
C) are tightly bound in place.
18. Why is metal, such as copper, used to ground buildings?
Because it is a good conductor
19. Electric charges are conserved. What does that mean?
They are not created nor destroyed.
20. What happens when you rub 2 objects together and create a static charge?
Electrons are transferred from one object to another.
21. When 2 charges are moved further apart so their distance is 5 times greater, the force between
them is 25 times smaller.
22. If you triple the charge of an object, what will happen to the force?
You triple the force.
23. Which of the following is an example of induction?
A) Walking across a carpeted floor
B) Rubbing a balloon on your arm
C) Making your hair stand up when you are touching the van de Graaf generator.
D) Moving a soda can with a negatively charged rod.
24. When drawing electron field lines, the arrows always point toward ( positive, negative ) objects
and away from ( positive, negative )
objects.
25. When an object is connected to the earth it is grounded.
26. If a charged object is brought closer to the knob of an electroscope, the force will
( increase, decrease )
27. Electric forces are ( directly, inversely ) proportional to charge and ( directly, inversely )
proportional to the distance.
28. Attractive electric field lines ( curve, are straight lines ) from one charged object ( towards,
away from ) the second charged object.
29. In your lab, when two pieces of tape were pulled from the surface, the pieces of tape repelled one
another because
A) They were oppositely charged
B) they became electrically charged.
C) they were conducting electricity
30. The reason a charged balloon will stick to a wall is that
A) electrons transfer back and forth between the wall and the balloon.
B) induced opposite charges in the wall attract the balloon.
31. Object A is rubbed against object B and object B becomes positively charged. Electrons were
transferred from object ( A, B ) to object ( A, B ).
32. What causes bits of paper to be attracted to a charged plastic comb? Electric charge
33. If I want to increase Electric Field strength, I would have to ( increase, decrease ) the charge?
34. Using the diagram to the right, which of the objects is
negatively charged? B
35. The diagram below shows particles that have ( opposite, the same ) charges.
36. The diagram below shows two charges that are ( attracting, repelling )
37. Use the diagram below:
Which charge has the greatest magnitude? __F__
Which charge has the weakest magnitude? __G__
38. The parallel lines shown below are ( oppositely charged, have the same charge, are neutral ).
Use the following equations to answer Questions (39 – 44)
F
E
K  q1  q 2
d2
F
|q|
d
K  q1  q 2
F
V
F d2
q2 
K  q1
W
q
K  9.0 x10 9
V  Ed
e- = 1.6 x 10-19
39. Two points on a cloud are both charged with +2 C. They are separated by a distance of 900 m.
What is the force acting between these two points?
F
K  q1  q 2
d2
(9 x109 )  (2)  (2)
F
(900) 2
F  44,444 N
40. The force of attraction between a – 50 μC and + 90 μC charge is 4.5 N. What distance separates
these two charges?
K  q1  q 2
F
d
d
(9 x10 9 )  (50 x10 6 )  (90 x10 6 )
 4.5
d  3m
41. A 2.5 C charge is 18 m from the second charge, and the force between them is 1.5 N. What is the
magnitude of the second charge?
F d2
q2 
K  q1
1.5  (18) 2
q2 
(9 x109 )  2.5
q 2  .000000022 C
q2 
486
2.25 x1010
OR 2.2 x 10-8 C
42. A .5 C charge experiences a 2.0 N force when placed at a certain location. What would the
electric field (E) at this location be?
E
F
|q|
𝐸=
2.0
.5
E = 4.0 N/C
43. An electron in a TV picture tube passes through a potential difference of 16,500 V. How much
work is done on the electron as it passes through the potential difference?
V
W
q
W
16,500 
1.6 x 10 - 19
1.6 x 10 -19  16,500 
W
 1.6 x 10 -19
-19
1.6 x 10
W = 2.64 x 10-15J
44. An electron in a TV tube moves 30 cm through an electric field of 500 N/C. How much potential
difference is created?
V  Ed
V  500  .30
V  150V