Physics 112 Exam 1

Front 1

What is:

Charge conservation

Back 1

The net amount of electric charge produced in any process is zero.

OR

No net electric charge can be created or destroyed.

Front 2

What is:

Charge Quantization

Back 2

An object cannot gain or lose a fraction of an electron, thus net charge is a multiple of e. (1e, 2e, 3e, etc).

-1uC is equivalent to 10^13 electrons

Front 3

Induced charge by conduction

Back 3

A + charge object and a neutral object briefly touch. Free e- from neutral object pass over to + object. Now both objects have a positive charge, and it was due to contact.

Front 4

Induced charge by induction

Back 4

A + object is close to a neutral one. Free e- in neutral object move toward the + object. No net charge has been created, but there's a separation in charge at opposite ends on the neutral object.

Front 5

Describe an electroscope.

Back 5

+ charge brought close to knob, separation of charge occurs (knob -, and leaves +). Leaves repel each other.

-To know sign of charge: charge by conduction and bring + charge by knob. If leaves close its b/c e- moved up to knob and were attracted to +.

Front 6

Describe an electrophorus

Back 6

A plastic (dielectric plate) is charged through the triboelectric effect (rubbing fur). A metal plate is placed on top and a separation of charge occurs. Touching the top of metal plate (grounding) removes the repelled charge and leave it with only the attractive charge.

Front 7

Define electric field

Back 7

The force felt by a smallpositive ‘test’ charge, q, divided by that charge.

OR

The electric force per unit charge

Front 8

Characteristics of electric field

-Force direction

-Field direction with point charge

Back 8

+q, E and F in same direction

-q, E and F in opposite direction

Electric field is vector that points away from + charges and toward - charges

Front 9

Define "net charge"

Back 9

The sum of all + and - charges in an object

Front 10

What is meant by the "free charge"

Back 10

Loosely bound electrons that can move freely around a conductor

Front 11

Electric flux refers to:

Back 11

The electric field passing through a given area. It is proportional to the number of field lines crossing the area.

Front 12

electric potential

Back 12

-It is the PE per charge

-It's used to express the effect of the source of an electric field in terms of the location within the electric field.

-Larger the Q, the larger the PE, but V remains the same.

Front 13

Difference between:

field lines and equipotential lines

Back 13

Field Lines: point away from + and toward - charges. Num of lines is proportional to charge magnitude.

Equipotential Lines: The potential difference along any point is 0. They are perpendicular to electric field lines. They are always continuous and never end.

Front 14

Understand how the electric potential varies inside a capacitor.

Back 14

Front 15

Define electronvolt

Back 15

One eV = energy acquired by a particle with charge of magnitude e when it moves through a potential difference of 1 volt.

=q(V)

Front 16

Electric field inside a capacitor is:

Back 16

NOT uniform.

-It can be conducted at any point (E=-V/x)

Front 17

The potential energy equals the _____ required to bring ______ _________ near each other from ______

Back 17

The potential energy equals the work required to bring two charges near each other from infinity.

Front 18

The amount of charge (Q) acquired by each plate is proportional to the magnitude of the ______ ______ between the plates. (equation)

Back 18

The amount of charge (Q) acquired by each plate is proportional to the magnitude of the potential difference (V) between the plates. (Q=CV)

Front 19

Capacitance value depends on ___, ___, and ___ of the two conductors. Not ____ or ____.

Back 19

Capacitance value depends on size, shape, and relative position of the two conductors, not charge or voltage.

Front 20

Equipotential lines between identical charges

Back 20

Front 21

Electric field of a point charge (equation)

Back 21

E = k (Q/r^2)

Front 22

Static electric field inside a conductor is _____; surface field is _______ to surface.

Back 22

Static electric field inside a conductor is zero; surface field is perpendicular to surface.

Front 23

Coulomb's Law

Back 23

F = k (Q1xQ2)/(r^2)

Front 24

Gauss's Law

Back 24

EA = Qencl/eo

eo = constant of permittivity

Front 25

What happens when a dielectric is inserted into a capacitor connected to a battery?

Back 25

-Battery keeps V constant

-C increases due to dielectric

-Q increases; more charge is pulled from battery (Q=CV)

Front 26

What happens when a dielectric is inserted into an isolated capacitor that has a charge Q on it?

Back 26

Q=CV

-C increases

-Because it is isolated, Q must stay the same and thus V must decrease as a result of C always increasing with a dielectric

Front 27

In non-spherical conductors, surface charge densities and electric potentials fields are _____ where the curvature is the greatest

Back 27

Biggest

Front 28

Change in potential energy when a charge qmoves through potential difference of V is:

Back 28

PE = qV

Front 29

Potential difference between r and ∞ due to point charge Q

Back 29

V = k (Q/r)

Front 30

Electric flux angle

Back 30

Angle between a perp. line with area and the electric Field

Front 31

A battery is a source of constant:

Back 31

Potential difference

Front 32

Electric current is the rate of flow of:

Back 32

Electric charge

Front 33

Conventional current is the direction that:

Back 33

positive charge would flow

Front 34

Ohmic materials have:

Back 34

Constant resistance

Front 35

Resistance of wire is determined by:

Back 35

shape and material

Front 36

Direct current is:

Alternating current:

Back 36

-is constant

-varies sinusoidally