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14 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

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Physics 300



Final

Exam

Review



Electrostatics







Mr.

Youker

|




Answer the multiple choice questions by placing the letter for the best answer on the line provided. Provide
complete solutions to the questions on the back in the space

provided. Do not use a separate piece of paper.


1
-
5. Definitions



• Electric field lines possess a vector direction that is…


a. toward positive charges


c. tangent to charged surfaces

b. toward negative charges


d. at a right angle to currents




• An excess of electrons will create a…


a. negative charge

b. positive charge


c. neutral charge


d. inverse charge





• The process of electrostatic induction produces…


a. negative charge

b. positive charge


c. char
ge separation d. charge inversion



• Ions promote the ability of a material to act as a(n)…


a. insulator


b. arbitrator


c. conductor d. perpetrator



• An electric field potential may be measured in units o
f…


a. A
.
m


b. J
.
m


c. J/C


d. C/s


6
-
10. Proportionalities



• A field near a point charge has a strength E. If you move twice as close to that charge the field will be...


a. E/4


b. E/2


c. E


d. 2E


e. 4E



• When an electron and a proton ar
e both released from rest within a uniform electric field…

a.

their accelerations will be different sizes and directions.

b.

their accelerations will be different sizes but the same direction.

c.

their accelerations will be the same size and but different direction
s.

d.

there is not enough information.



• A charged metal sphere A (r
A

= 20 cm) is touched to a neutral metal sphere B (r
B

= 10 cm).

When equilibrium is reached…


a. q
A

= q
B
=

0


b. q
A

= q
B
≠ 0


c. q
A

< q
B

d. q
A

> q
B




• If the separation of two
oppositely charged metal plates is doubled and an electron accelerates
through the space between them, its final kinetic energy will be…


a. double


b. halve



c. remain unchanged



• A metal box is charged. The charge concentration will be greates
t


while it will
least


.


a. on the faces; on the corners


c.

on the corners; on the faces



b. on the faces; on the inside



d.

on the corners; on the inside



11
-
15. Basic Problems



• T
he electric field strength 3 m away from a 2 nC charge will be…


a. 1 N/C


b. 2 N/C


c. 6 N/C


d. 18 N/C



• The electric field strength midway between two charged parallel plates will be


if they
carry a voltage of 100 V and have
a separation of 4 cm.


a. 4 N/C


b. 25 N/C

c. 2500 N/C

d. 4000 N/C



• The number of excess electrons on 2

C charged pith ball is approximately…


a. 10
3


b. 10
13


c. 10
23


d. 10
3
3



• When a +5 C charge accelerates through 20 V of potential difference, its increase in energy will be…


a. 4 J


b. 20 J


c. 100 J


d. 400 J



• How much force will a +5C

charge experiecne when placed into a field of strength 100 N/C?


a. 2 N


b. 5 N


c. 20 N


d. 500 N






Level 1


Problem



How much electrical attraction exists between a proton and an electron positioned 4.0 mm apart?












Level 2


Problem

• A +2

nC charge is released from rest at a distance 50 cm away from a charged (Q = +3

C) van de Graaff
sphere. What will its initial acceleration be when released?














Level 3


Problem



What is the size of the net electric field at the origin, if there is a +3 nC charge at x = 2 m and a
-
6 nC
charge at y = 4 m?























Physics
300



Final

Exam

Review



Electrostatics

-

ANSWERS





Mr.

Youker

|




Answer the multiple choice questions by placing the letter for the best answer on the line provided. Provide
complete solutions to the questions on the back

in the space provided. Do not use a separate piece of paper.


1
-
5. Definitions


B


Electric field lines possess a vector direction that is…


a.
toward positive charges


c. tangent to charged surfaces

b.
toward negative charges


d.

at a right angle to

currents


A

• An excess of electrons will create a…


a.
negative charge

b.
positive charge


c.
neutral charge


d.
inverse charge





C

• The process of electrostatic induction produces…


a. negative charge

b.
positive charge



c.
charge separation
d.
charge inversion


C


Ions promote the ability of a material to act as a(n)…


a.
insulator


b. arbitrator


c.
conductor
d.
perpetrator



C


An electric field potential may be measured in

units of…


a.
A
.
m


b.
J
.
m


c.
J/C


d.
C/s


6
-
10. Proportionalities


E

• A field near a point charge has a strength E. If you move twice as close to that charge the field will be...


a.
E/4


b.
E/2


c.
E


d. 2E


e. 4E


A


When an electron and a pro
ton are both released from rest within a uniform electric field…

a.

their accelerations will be different sizes and directions.

b.

their accelerations will be different sizes but the same direction.

c.

their accelerations will be the same size and but different dir
ections.

d.

there is not enough information.


D

• A charged metal sphere A (r
A

= 20 cm) is touched to a neutral metal sphere B (r
B

= 10 cm).

When equilibrium is reached…


a.
q
A

= q
B
=

0


b. q
A

= q
B
≠ 0


c
.
q
A

< q
B

d
.
q
A

> q
B



B

• If the separation of
two oppositely charged metal plates is doubled and an electron accelerates
through the space between them, its final kinetic energy will be…


a. double


b. halve



c. remain unchanged


D


A metal box is charged. The charge concentration will be grea
test


while it will
least


.


a.
on the faces; on the corners


c
.

on the corners; on the faces



b
.
on the faces; on the inside



d.

on the corners; on the inside



11
-
15. Basic Problems


B



The electric field strength 3 m away from a 2 nC charge will be…


a.
1 N/C


b. 2

N/C


c.
6 N/C


d.
18 N/C


C

• The e
le
ctric field stre
n
gth midway between two charged parallel plates will be


if they
carry a voltage of 100 V and have

a separation of 4 cm.


a. 4 N/C


b. 25 N/C

c. 2500 N/C

d. 4000 N/C


B


The number of
exces
s electrons on 2

C charged pith ball is approximately…


a.
10
3


b.
10
13


c.
10
23


d.
10
3
3


C

• When a +5 C charge
accelerates through 20 V of potential difference, its increase in energy will be…


a.
4 J


b.
20 J


c. 100 J


d. 400 J


D


How much force will a +5C c
harge experie
n
c
e when placed into a field of strength 100 N/C?


a. 2

N


b.
5

N


c.
20
N


d.
500

N






Level 1


Problem



How much electrical attraction exists between a proton and an electron positioned 4.0 mm apart?


F = KQq/r
2

F = (9 x10
9
)(1.6 x10
-
19
)(
1.6 x10
-
19
) / (0.004)
2

F = 1.44 x10
-
23

N








Level 2


Problem


A +2 nC charge is released from rest at a distance 50 cm away from a charged (Q = +3

C) van de Graaff
sphere. What will its initial acceleration be when released?


a = F/m



F = KQq/r
2

a =

0.000216/m


F = (9 x10
9
)(2 x10
-
9
)(3 x10
-
6
) / (0.50)
2




F = 0.000216 N

Oops… need mass!










Level 3


Problem



What is the size of the net electric field at the origin, if there is a +3 nC charge at x = 2 m and a
-
6 nC
charge at y = 4 m?


E
1

= KQ
1
/r
2



E
2

= KQ
2
/r
2

E
1

= (9 x10
9
)(3 x10
-
9
)/2
2


E
2

= (9 x10
9
)(6 x10
-
9
)/4
2

E
1

= 6.75 N/C



E
2

=
3
.
3
75 N/C


E
net
2

= E
1
2

+ E
2
2

E
net
2

= 6.75
2

+ 3.375
2

E
net

= 7.55 N/C