Chapter 5 - Electrostatics and Magnetism

Question 1

Fundamental Unit of Charge value:

Answer 1

e = 1.60 x 10¹⁹ C

• Proton q = +e*
• Electron q = -e*

Question 2

Law of conservation of charge:

Answer 2

charge can neither be created nor destroyed

Question 3

Insulator:

1. distribution of charge
2. how electrons are linked
3. examples of insulators

Answer 3

will not easily distribute charge over its surface and will not transfer that charge to another neutral object very well - especially not to another insulator

Electrons tend to be closely linked with their respective nuclei

Nonmetals are insulators

Question 4

Conductor:

1. what charges will do
2. what they can do
3. what they are used for
4. examples

Answer 4

when given a charge, the changes will distribute approximately evenly upon the surface on the conductor

Able to transfer and transport charges

Used in circuits + electrochemical cells

Generally metals

Question 5

Coulomb’s Law:

1. what it does
2. equation + variables

Answer 5

quantifies the magnitude of the electrostatic force Fc, between two charges

F_e = magnitude of the electrostatic force
k = coulombs constant
q1 & q2 = magnitude of the two charges
r = distance between the two charges

Question 6

Coulomb’s Constant:

(equation + value)

Answer 6

Question 7

Permittivity of free space value:

Answer 7

e₀

Question 8

Electric fields:

1. what they do
2. test charge
3. source charge

Answer 8

1. exert forces on other charges that move into the space of the field
2. Test charge (q): charged placed in electric field
3. Source charge (Q): actually creates electric field
   * Can be opposite or attractive forces*

Question 9

Electric Field Magnitude equation + variables:

Answer 9

E = electric field magnitude (N/C)
F<sub>e</sub> = magnitude of the force felt by the test charge q
k = electrostatic constant
Q = source charge magnitude
r = distance between the charges

Question 10

Electric field vectors for Positive and Negative charges:

Answer 10

Positive charges = electric field vectors radiate outward (point away)

Negative charges = electric field vectors radiate inward (point toward)

Question 11

Electric Potential Energy:

1. what it is
2. regular equation

Answer 11

Question 12

Change in Electrical Potential Energy derivation:

Answer 12

Question 13

Electrical potential:

1. what it is
2. 2 equations

Answer 13

the ratio of the magnitude of a charge’s electrical potential energy to the magnitude of the charge itself

V = electrical potential (1V = 1J/C)

Question 14

Potential Difference:

1. also known as what
2. equation

Answer 14

voltage difference

Question 15

Relationship between the movement of charges and electrical potential:

1. positive charges
2. negative charges
3. in both cases

Answer 15

1. Positive charges will spontaneously move in the direction that decreases their electrical potential (negative voltage)
2. Negative charges will spontaneously move in the direction that increases their electrical potential energy (positive voltage)
3. In both cases: the electrical potential energy is decreasing

Question 16

Equipotential Lines:

Answer 16

line on which every potential is the same

The potential difference between any two points on an equipotential line is zero

Question 17

Electric dipoles:

1. what it is a result of

Answer 17

results from two equal and opposite charges being separated a small distance d from each other

Can be transient or permanent (molecular dipole of water)

Question 18

Electric Dipole voltage equation:

Answer 18

Question 19

Dipole Moment equation: (+ units)

Answer 19

p = qd

d = distance between two dipoles

Question 20

Net Torque on a Dipole:

Answer 20

Question 21

Diamagnetic materials:

1. what they are
2. examples

Answer 21

made of atoms with no unpaired electrons and that have no net magnetic field

Common materials you wouldn’t expect to get stuck to a magnet

Question 22

Paramagnetic materials:

1. what they do
2. examples

Answer 22

1. will become weakly magnetized in the presence of an external magnetic field, aligning the magnetic dipoles of the material with the external field
2. Aluminum, copper and gold

Question 23

Ferromagnetic materials:

1. how they behave
2. when they become strongly magnetized
3. examples

Answer 23

have unpaired electrons and permanent atomic magnetic dipoles that are normally oriented randomly so that the material has no net magnetic dipole

Will become strongly magnetized when exposed to a magnetic field under certain temperatures

Iron, nickel cobalt

Question 24

Magnetic Fields - Infinietly long straight current-carrying wire equation + variables:

Answer 24

B = magnetic field distance r from the wire
r = perpendicular distance
µ<sub>0</sub> = permeability of free space
I = current

Question 25

Permeability of free space value:

Answer 25

µ₀

Question 26

Magnetic Field for a circular loop of a current-carrying wire equation:

Answer 26

r = radius

Question 27

Right Hand Rule for Magnetic Fields with wires:

Answer 27

To determine the direction of the field vectors - RHR rule Point thumb in the direction of the current Wrap your fingers around current carrying wire Fingers mimic circular field lines, curing around the wire

Question 28

Lorentz force:

Answer 28

sum of both the electrostatic and magnetic forces acting on charges at the same time

Question 29

Force on a moving charge: 1. what a magnetic force acts on 2. equation + variables

Answer 29

1. A magnetic force can be exerted on a charge moving in a magnetic field **2. F_B = qvB sinθ** ``` q = charge v = magnitude of velocity B = magnitude of the magnetic field Θ = smallest angle between the velocity vector and the magnetic field vector B ```

Question 30

Right Hand Rule to determine the direction of the magnetic force on a moving charge: also applicable to force on a current-carrying wire

Answer 30

Position thumb in the direction of the velocity vector Put fingers in the direction of the magnetic field lines Palm will point in the direction of the force vector for a positive charge Back of hand will point in the direction of the force vector for a negative charge

Question 31

Force on a Current-Carrying Wire: 1. when placed in a magnetic field... 2. equation for a straight wire and variables

Answer 31

1. Current-carrying wire placed in a magnetic field may also experience a magnetic force 2. For a straight wire: **F_B = ILB sinθ** ``` I = current L = length of the wire in the field B = magnitude of the magnetic field Θ = angle between L and B ```