Chapter 5 - Electrostatics and Magnetism Flashcards
Fundamental Unit of Charge value:
e = 1.60 x 1019 C
- Proton q = +e*
- Electron q = -e*
Law of conservation of charge:
charge can neither be created nor destroyed
Insulator:
- distribution of charge
- how electrons are linked
- examples of insulators
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
Conductor:
- what charges will do
- what they can do
- what they are used for
- examples
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
Coulomb’s Law:
- what it does
- equation + variables
quantifies the magnitude of the electrostatic force Fc, between two charges
Fe = magnitude of the electrostatic force
k = coulombs constant
q1 & q2 = magnitude of the two charges
r = distance between the two charges
Coulomb’s Constant:
(equation + value)
Permittivity of free space value:
e0
Electric fields:
- what they do
- test charge
- source charge
- exert forces on other charges that move into the space of the field
- Test charge (q): charged placed in electric field
-
Source charge (Q): actually creates electric field
* Can be opposite or attractive forces*
Electric Field Magnitude equation + variables:
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
Electric field vectors for Positive and Negative charges:
Positive charges = electric field vectors radiate outward (point away)
Negative charges = electric field vectors radiate inward (point toward)
Electric Potential Energy:
- what it is
- regular equation
Change in Electrical Potential Energy derivation:
Electrical potential:
- what it is
- 2 equations
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)
Potential Difference:
- also known as what
- equation
voltage difference
Relationship between the movement of charges and electrical potential:
- positive charges
- negative charges
- in both cases
- Positive charges will spontaneously move in the direction that decreases their electrical potential (negative voltage)
- Negative charges will spontaneously move in the direction that increases their electrical potential energy (positive voltage)
- In both cases: the electrical potential energy is decreasing
Equipotential Lines:
line on which every potential is the same
The potential difference between any two points on an equipotential line is zero
Electric dipoles:
- what it is a result of
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)
Electric Dipole voltage equation:
Dipole Moment equation: (+ units)
p = qd
d = distance between two dipoles
Net Torque on a Dipole:
Diamagnetic materials:
- what they are
- examples
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
Paramagnetic materials:
- what they do
- examples
- will become weakly magnetized in the presence of an external magnetic field, aligning the magnetic dipoles of the material with the external field
- Aluminum, copper and gold
Ferromagnetic materials:
- how they behave
- when they become strongly magnetized
- examples
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
Magnetic Fields - Infinietly long straight current-carrying wire equation + variables:
B = magnetic field distance r from the wire r = perpendicular distance µ<sub>0</sub> = permeability of free space I = current
Permeability of free space value:
µ0
Magnetic Field for a circular loop of a current-carrying wire equation:
r = radius
Right Hand Rule for Magnetic Fields with wires:
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
Lorentz force:
sum of both the electrostatic and magnetic forces acting on charges at the same time
Force on a moving charge:
- what a magnetic force acts on
- equation + variables
- A magnetic force can be exerted on a charge moving in a magnetic field
2. FB = 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
Right Hand Rule to determine the direction of the magnetic force on a moving charge:
also applicable to force on a current-carrying wire
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
Force on a Current-Carrying Wire:
- when placed in a magnetic field…
- equation for a straight wire and variables
- Current-carrying wire placed in a magnetic field may also experience a magnetic force
- For a straight wire:
FB = ILB sinθ
I = current L = length of the wire in the field B = magnitude of the magnetic field Θ = angle between L and B
