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

### 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