Exam 1 Flashcards

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1
Q

q=Ne
q=

A

charge

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2
Q

q=Ne
N=

A

number of electrons

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3
Q

q=Ne
e=

A

charge on a single electron

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4
Q

charge is a _____ force

A

conservative

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5
Q

if an object is polarized, it means…

A

charges shift in a neutral object

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6
Q

conductors vs insulators

A

conductors:
metals
allow e- to transfer

insulators:
plastic
hold e- more tightly

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7
Q

µ =

A

10^-6

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8
Q

F=k (q1q2/r^2)
F=

A

force

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9
Q

F=k (q1q2/r^2)
k=

A

Coulomb’s constant
9x10^9

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10
Q

F=k (q1q2/r^2)
q=

A

charge on that specific object

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11
Q

F=k (q1q2/r^2)
r=

A

the distance between q1 and q2

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12
Q

given q=18µC and d=15cm, find magnitude and direction on force 1.
q1 = +q
q2 = -2.0q
q3 = +3.0q

A
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13
Q

-3.00µC in the center of a compass. 2 additional charges are on the center (r=.100m). -4.0µC due north and +5.0µC due east.
find the direction and magnitude of the charge in the center.

A
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14
Q

an electron moves at 8.5x10^5m/s. what is the radius?

A
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15
Q

+q placed in an electric field will accelerate _____ the field (gravity)

A

with

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16
Q

-q placed in an electric field will accelerate _____ the field (gravity)

A

against

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17
Q

density of electric field lines relates to the ______ of E

A

magnitude

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18
Q

2 point charges are placed on an x-axis. -5.5µC at the origin and 8.5µC ar x=10cm.
what is the net electric field at x=-4cm?

A
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19
Q

2 point charges are placed on an x-axis. -5.5µC at the origin and 8.5µC ar x=10cm.
what is the net electric field at x=4cm?

A
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20
Q

2 point charges are placed on an x-axis. -5.5µC at the origin and 8.5µC ar x=10cm.
where is the net field =0?

A

E+ = E-
0.41m left

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21
Q

an electron enters a capacitor with v=5.75x10^6m/s. it has a downward distance of d=0.638 and a horizontal length of 2.25cm.
what is the magnitude of the electric field?

A
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22
Q

an electron is placed between plates of a parallel plate capacitor. when released, it remains balanced.
what is the magnitude and direction of the electric field

A

F=ma
FE-Fg = 0
FE=Fg
qE=mg
E=mg/q
E= 5.58x10^-11 N/C downward

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23
Q

an electron is placed between plates of a parallel plate capacitor. when released, it remains balanced.
if gravity is turned off, what is the acceleration if a proton is released?

A

F=ma
0-FE=ma
-qE=ma
a=-qE/m
a=5.34x10^-3 m/s^2 downward

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24
Q

ideal conductors have
_____ charge
fields _____ and at _____
and _____ shielding

A

excess
inside and at surface
electron shielding

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25
Q

point charge:

A

E=kd/r^2

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26
Q

voltage = ________

A

electrical potential

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27
Q

do you use signs in k(q1q2/r^2)

A

NO!

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28
Q

moving against gravity = ______ height

A

gaining

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29
Q

moving against electric field = ______ voltage

A

gain

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30
Q

moving with the electric field = ______ voltage

A

lose

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31
Q

W = -q∆V
W=

A

work

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32
Q

W = -q∆V
q=

A

charge

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33
Q

W = -q∆V
V=

A

change in potential/voltage

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34
Q

E=- ∆V/∆d
E=

A

electric field

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35
Q

E=- ∆V/∆d
V=

A

potential difference

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36
Q

E=- ∆V/∆d
d=

A

distance between plates

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37
Q

____ decreases when you move with gravity

A

height

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38
Q

______ decreases when you move with the electric field

A

potential/voltage

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39
Q

a ______ mass accelerates against the gravitational field from a high to low gravitational height

A

positive

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40
Q

a positive mass accelerates _____ the gravitational field form a high to low gravitational height

A

against

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41
Q

a ______ charge accelerates with the electric field from a high to low electrical height

A

positive

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42
Q

a positive charge accelerates _____ the electric field from a high to low electrical height

A

with

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43
Q

a positive charge is moving with the field
q∆V = -We = ∆EPE

A

q∆V = -We = ∆EPE
+ - - (+) -

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44
Q

a negative charge is moving with the field
q∆V = -We = ∆EPE

A

q∆V = -We = ∆EPE
- - - (-) +

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45
Q

a positive charge is moving against the field
q∆V = -We = ∆EPE

A

q∆V = -We = ∆EPE
+ + - +

46
Q

a uniform electric field points in the negative y and magnitude of 4300N/C
what is the electrical potential difference between Vb-Va?

A

0V

47
Q

a uniform electric field points in the negative y and magnitude of 4300N/C
what is the electrical potential difference between Vc-Vb?

A

∆V=E∆d
344V

48
Q

a uniform electric field points in the negative y and magnitude of 4300N/C
what is the electrical potential difference between Va-Vc?

A

∆V=E∆d
-344V

49
Q

energy conservation:

A

1/2mva^2 + qVa = 1/2mvb^2 + qVa

50
Q

electrons in a tv set accelerate from rest at point A at a potential difference of 25kV to point B
_____ has the higher potential energy

A

B

51
Q

electrons in a tv set accelerate from rest at point A at a potential difference of 25kV to point B
the electric field points from _____

A

B -> A

52
Q

electrons in a tv set accelerate from rest at point A at a potential difference of 25kV to point B
what is the speed of the electrons when they arrive at B?

A
53
Q

finding the electrical potential for a point charge:

A

V=k (q/r)

54
Q

equipotential surfaces are always _____ to electrical field lines

A

perpendicular

55
Q

height _____ when moving away from the center

A

decreases

56
Q

+4.0µC is placed at x=0 and -8µC 10cm to its right.
what is the potential at the midpoint?
what is the potential at 15cm?

A
57
Q

a charge A of -3.0µC is fixed. from a horizontal distance of 0.0450m, a particle with mass 7.20x10^-3kg and a charge of -8.0µC is fired with an initial speed 165m/s towards a fixed charge (B).
how far from charge is the particle when the speed is
(a) 150m/s?
(b) 0m/s?

A
58
Q

x=0.25m and y=0.16m
how much work is needed to assemble all 3 charges?

A
59
Q

describe a capacitor

A

has “capacity” to store both electrical charge and energy (via) field

60
Q

capacitors are dependent on _____ and _____

A

geometry
composition

61
Q

describe a dialectric

A

“stomps down” the electric field by polarization (trash back example)

62
Q

Ohm’s law: V=IR
V=

A

voltage

63
Q

Ohm’s law: V=IR
I=

A

current

64
Q

Ohm’s law: V=IR
R=

A

resistance

65
Q

low voltage = _____ resistance

A

low

66
Q

2 ways to change resistance

A

geometry
composition

67
Q

R=p L/A
R=

A

resistance of a wire

68
Q

R=p L/A
p=

A

resistivity

69
Q

R=p L/A
L=

A

length

70
Q

R=p L/A
A=

A

cross sectional area

71
Q

more resistance = _____ resistance

A

less

72
Q

increased area = _____ resistance

A

decreased

73
Q

increased length = _____ resistance

A

increased

74
Q

conductors _____ resistance

A

decrease

75
Q

inductors _____ resistance

A

increase

76
Q

an average tv set runs 6 hours a day. calculate the yearly cost of 100 million TVs when power consumptions is 165W and it costs 12.5c kW/hr

A
77
Q

junction rule:

A

Iout = Iin

78
Q

loop rule:

A

Vdrop = Vgain

79
Q

big loop clockwise:

A

Vdrop = Vgain
5I2 + 18V + 10I3 = 13V

80
Q

left loop counterclockwise:

A

Vdrop = Vgain
13V = 5I2 + 2V + 10I2

81
Q

right loop counterclockwise:

A

Vdrop = Vgain
18V + 10I3 = 2V + 10I2

82
Q

ammeters connect in _____ so there is _____ resistance

A

series
zero

83
Q

voltmeters connect in _____ so there is _____ resistance

A

parallel
infinite

84
Q

F=qe
F=

A

force

85
Q

F=qE
E=

A

electric field intensity

86
Q

F=qvB
v=

A

velocity

87
Q

F=qvB
B=

A

magnetic field intensity

88
Q

right hand rule:
thumb is _____
fingers are _____
palm faces _____ and is ______

A

velocity
field
up, force

89
Q

motion of charge in a B field?

A

F=ma
qvB=m(v^2/r)
r=mv/qB

90
Q

a charged conductor is brought near an uncharged insulator. what happens to the objects?

A

they attract eachother

91
Q

consider 3 identical spheres, A, B, and C. sphere A carries a charge of -2.0µC; sphere B carries a charge of -6.0µC; and sphere C carries a charge of +4.0µC. Sphere A and B touch and then separate. Sphere B and C touch and then separate.
What is the charge on C?

A

0

92
Q

a -4.0µC charge is located 0.4m to the left of a +6.0µC charge. what is the magnitude and direction of the electrostatic force on the positive charge?

A
93
Q

an electron is located between the plates of a parallel plate capacitor. what is the magnitude and direction of the electronic field such that the electric force exactly balances the weight of the electron so it remains stationary?

A

qE=mg
E=mg/q
E=5.6x10^-11 N/C

94
Q

the electron volt is a unit of _____

A

energy

95
Q

as an electron moves against an electric field, its electric potential _____ and potential energy ______

A

increases
decreases

96
Q

2 point charges are held at the corners of a rectangle. h=0.050m and w=0.15m. what is the electric potential at point A?

A
97
Q

what is the change in electric potential when a charge of -1.0µC is moved from A to F to C to E?

A
98
Q

what way does the electric field point?

A

D

99
Q

the potential difference across the ends of a wire doubles in magnitude. how does this effect the resistance?

A

no change
can only be changed by geometry or composition

100
Q

resistors in series have the same _____ through them

A

current

101
Q

resistors in parallel have the same ______ through them

A

voltage

102
Q

for resistors in parallel the total resistance is _____ any singular resistors

A

less than

103
Q

for resistors in series, the total resistance is ______ any single resistor

A

greater than

104
Q

what is the total resistance of the circuit?

A
105
Q

what is the current through the 1.8Ω resistor?
a) 3.3
b) 2.8
c) 14
d) 6.9
e) 5.6

A

V=IR
Ibat = V/R
25/7.5 = 3.33A
I1.8 must be < I bat so
2.8

106
Q

the length of a wire is kept the same but the radius is doubled. this causes the resistance to ______ by a factor of ______

A

decrease
4

107
Q

a 4A circuit is maintained in a simple circuit with a total resistance of 2Ω. how much energy is delivered in 45s?

A

V=IR
V=(4)(2) = 8V
P=IV
P=(4)(8) = 32W
P=energy/time
energy=Pt
(32)(45) = 1440J

108
Q

if the current is 2A, what is the voltage?

A

V=IR
(2)(3) = 6V

109
Q

kirchoff’s loop rule is a statement of the law of conservation of _____

A

energy

110
Q

left loop clockwise
Vdrop = Vgain

A

12I2 + 8I2 = 4V + 6V

111
Q

right loop clockwise
Vdrop = Vgain

A

4V + 2V = 6I3 + 8I2

112
Q

whole loop clockwise
Vdrop = Vgain

A

12I2 + 2V = 6I3 + 6V