Physics: E & M Flashcards Preview

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Flashcards in Physics: E & M Deck (42):
1

Conductors

Silver, Copper, Aluminum, Iron, Mercury, Carbon, Water

2

Conductors

Silver, Copper, Aluminum, Iron, Mercury, Carbon, Water

3

Semiconductors

Germanium, Silicon

4

Insulators

Dry Air, Wood, Glass, Rubber

5

A positive charge is deposited on the left side of a metal sphere. Why does the positive charge distribute itself uniformly throughout the surface of the sphere?

Excess electrons from the rest of sphere are attracted to the excess protons

6

A rubber balloon possesses a positive charge. If brought near and touched to a wooden door, it sticks to the door. This does not occur with an uncharged balloon. The wooden door must be

a) electrically neutral
b) negatively charged
c) a conductor
d) lacking electrons

a) electrically neutral

7

Coulomb's Law

F=kQq/r^2

(see application of inverse square)

8

Following Coulomb's Law,
If force is decreased by a factor of 4. What happens to distance?

Increased by a factor of 2

9

Following Coulomb's Law,
If force is increased by a factor of 9. What happens to distance?

Decreased by a factor of 3

10

Following Coulomb's Law,
If distance is decreased by a factor of 10. What happens to force?

increased by a factor of 100

11

Following Coulomb's Law,
If distance is increased by a factor of 5. What happens to force?

decreased by a factor of 25

12

What is true of the electrical potential energy (E) if charges are opposite?

E < 0

E is proportional to -1/r

13

What is true of the electrical potential energy (E) if charges are opposite?

E > 0

E is proportional to 1/r

14

Electric Potential
Conceptual Review:

(Volt = J/C)

•• A charge Q produces an E and V around it uniformly
(E and V lines are perpendicular). •

• The magnitude of E and V decrease as distance from Q increases.

•• The magnitude of E and V produced by Q increases as
Q increases. •

• An electric force exists only if a second charge is
placed in the electric field of Q. •

• A system has electrical potential energy only if a
second charge is present.

15

What physics concepts
appliy the inverse square law
ie: X = 1/r^2

Force of Gravity
Force of Electrostatics
Intensity: power/area
I is proportional to 1/r^2

16

How do you change the energy of a wave

interference (constructive/destructive)

17

Units of spring constant k

N/m

18

Electric field (N/C)

E= F/q = (kQq/r^2)/q
E=kO/r^2

vector: curved lines that never intersect

19

Why can't lines criss-cross in an electric field?

Cannot have 2 possible directions in one point in space

20

What does low density (spread out lines) in an electric field line

shows Weak field

Happens on outer part of field, bc E decreases as r increases (per inverse square law)

21

What can you tell about the spread and direction of arrows pointing in a field?

(Slide 10)

Negative charges point IN
Positive point out

MOre lines means higher density, means absolute value of Q is greater than a Q of few / more spread out lines

22

Potential Energy

F x d = kQq/r^2 x r = kQq/r

23

Semiconductors

Germanium, Silicon

24

Insulators

Dry Air, Wood, Glass, Rubber

25

A positive charge is deposited on the left side of a metal sphere. Why does the positive charge distribute itself uniformly throughout the surface of the sphere?

Excess electrons from the rest of sphere are attracted to the excess protons

26

A rubber balloon possesses a positive charge. If brought near and touched to a wooden door, it sticks to the door. This does not occur with an uncharged balloon. The wooden door must be

a) electrically neutral
b) negatively charged
c) a conductor
d) lacking electrons

a) electrically neutral

27

Coulomb's Law

F=kQq/r^2

(see application of inverse square)

28

Following Coulomb's Law,
If force is decreased by a factor of 4. What happens to distance?

Increased by a factor of 2

29

Following Coulomb's Law,
If force is increased by a factor of 9. What happens to distance?

Decreased by a factor of 3

30

Following Coulomb's Law,
If distance is decreased by a factor of 10. What happens to force?

increased by a factor of 100

31

Following Coulomb's Law,
If distance is increased by a factor of 5. What happens to force?

decreased by a factor of 25

32

What is true of the electrical potential energy (E) if charges are opposite?

E < 0

E is proportional to -1/r

33

What is true of the electrical potential energy (E) if charges are opposite?

E > 0

E is proportional to 1/r

34

Electric Potential
Conceptual Review:

(Volt = J/C)

•• A charge Q produces an E and V around it uniformly
(E and V lines are perpendicular). •

• The magnitude of E and V decrease as distance from Q increases.

•• The magnitude of E and V produced by Q increases as
Q increases. •

• An electric force exists only if a second charge is
placed in the electric field of Q. •

• A system has electrical potential energy only if a
second charge is present.

35

What physics concepts
appliy the inverse square law
ie: X = 1/r^2

Force of Gravity
Force of Electrostatics
Intensity: power/area
I is proportional to 1/r^2

36

How do you change the energy of a wave

interference (constructive/destructive)

37

Units of spring constant k

N/m

38

Electric field (N/C)

E= F/q = (kQq/r^2)/q
E=kO/r^2

vector: curved lines that never intersect

39

Why can't lines criss-cross in an electric field?

Cannot have 2 possible directions in one point in space

40

What does low density (spread out lines) in an electric field line

shows Weak field

Happens on outer part of field, bc E decreases as r increases (per inverse square law)

41

What can you tell about the spread and direction of arrows pointing in a field?

(Slide 10)

Negative charges point IN
Positive point out

MOre lines means higher density, means absolute value of Q is greater than a Q of few / more spread out lines

42

Potential Energy

F x d = kQq/r^2 x r = kQq/r