Lect 7: Electricity and Magnetism Flashcards by Taylor Walker

intrinsic property of some subatomic particles
positive and negative 1.6 * 10^-19 C
quantied to discrete levels
SI Unit = Coulomb

charge (q)

How well did you know this?

Not at all

Perfectly

universe has 0 net charge; Net charge is created by separating electrons from protons
If a negative charge is created, a positive charge must be created

law of conservation of charge

How well did you know this?

Not at all

Perfectly

describes the magnitude of the force of attraction / repulsion between two charged objects (point charges)

Coulomb’s Law

How well did you know this?

Not at all

Perfectly

Equation: Coulomb’s Law

F = k * q1 * q2 / r^2

Note: k = Coulomb’s constant = 8.9 * 10^9 N*m^2 / C^2

How well did you know this?

Not at all

Perfectly

point where the charge of an object is considered to originate

center of charge

How well did you know this?

Not at all

Perfectly

concept to explain action at a distance

create forces of gravity, electricity, and magnetism

field

How well did you know this?

Not at all

Perfectly

represent any field
point in the direction of a field: Positive —> Negative
relative distance between lines shows strength of field
can never intersect

lines of force

How well did you know this?

Not at all

Perfectly

electrostatic force per unit charge
vector in the direction of the field
SI Unit = N/C or V/ m

electric field (E)

How well did you know this?

Not at all

Perfectly

Equation: Electric Field from a point charge

E = k * q / r^2

SI Unit: N / C

How well did you know this?

Not at all

Perfectly

Equation: Electrostatic force on a point chargee

F = E * q

How well did you know this?

Not at all

Perfectly

Equation: Potential Energy (U) of a point charge in an electric field

U = F * d = E * q * d
SI Unit: Joule
Note: d = displacement from arbitrary 0 point

How well did you know this?

Not at all

Perfectly

the potential for work by an electric field in moving any charge by a distance (d)
SI Unit = Volts (V) and J/C

voltage

How well did you know this?

Not at all

Perfectly

Equation: Voltage

V = E * d

How well did you know this?

Not at all

Perfectly

Equation: Voltage due to a point charge

V = k * q / r
SI = V or J/C

How well did you know this?

Not at all

Perfectly

Work done by an electric field is _______ of the path because the field conserves mechanical energy

independent

How well did you know this?

Not at all

Perfectly

movement perpendicular to the electric field doesn’t cause a change in potential; all points on this surface are at the same voltage

equipotential surface

How well did you know this?

Not at all

Perfectly

created by two opposite charges w/ equal magnitudes; aligns itself in the opposite orientation to the field when placed in an electric field

electric dipole

How well did you know this?

Not at all

Perfectly

allows electrons to flow relatively freely; holds excess charge on the surface of the material; if uniformly charged, the electric field = 0
Ex: Metal

conductor

How well did you know this?

Not at all

Perfectly

holds electrons tightly in place; poor conductors

Ex: network solids (glass, diamond)

resistors

How well did you know this?

Not at all

Perfectly

to charge a conductor w/ a charged object
Ex: negatively charged rod placed near a good conductor that is near a second conductor causes electrons to move from the first to the second conductor, leaving the first one w/ a positive charge

induction

How well did you know this?

Not at all

Perfectly

a moving charge; scalar quantity
flow is in the direction of POSITIVE charge; created by the flow of electrons but is in the direction that a positive charge would flow
SI = Amp (A) or C/sec

current (I)

How well did you know this?

Not at all

Perfectly

cyclical pathway for a moving charge

circuit

How well did you know this?

Not at all

Perfectly

quantitative measure of how a substance resists the flow of charge

resistivity (rho)

How well did you know this?

Not at all

Perfectly

quantitative measure of an object w/ a certain shape/size to resist flow of charge; if the length of wire / area is cut in half, the object’s ___ is doubled
proportional to LENGTH and inversely proportional to AREA
SI Unit = Ohm (Ω)

resistance (R)

How well did you know this?

Not at all

Perfectly

product of R and I = voltage (V); equation used to analyze circuits

Ohm's Law

Equation: Ohm's Law

V = I*R

a current flowing into a node must = the current flowing out; (A node is any INTERSECTION of wires)

Kirchoff's 1st rule

voltage around any path in a circuit must sum to 0

Kirchoff's second rule

measurement used to rate batteries, which add energy to increase the voltage between two points Note: Assume NO internal resistance on MCAT

Electromotive Force (EMF)

used to temporarily store energy in a circuit in a separated charge

capacitor

two conductive plates separated by a small distance; 2 plates hold = amounts of opposite charges; creates a constant electric field between the two plates

parallel plate capacitor

the ability to store charge / unit voltage; a substance with high _____ can store a lot of charge at low voltage proportional to charge and inversely proportional to voltage --charge is only on the inside face of each plate; thickness of the plates does not affect charge stored

capacitance

Each unit of charge added causes the _______ to increase proportionally

voltage

Equation: Charge w/ capacitance & voltage | graph produces straight line; area under the curve = Energy (Q * V)

Q = C * V

Equation: Capacitance | SI Unit: Farad (F)

C = Q / V

Equation: Energy (U) stored by a Capacitor w/ charge and voltage

U = 1/2 * Q * V

Equation: Energy (U) stored by a Capacitor w/ capacitance and voltage

U = 1/2 * C * V^2

Equation: Energy (U) stored by a capacitor w/ charge and capacitance

U = 1/2 * Q^2 / C

substance between the plates of a capacitor; must be an insulator resists creation of an electric field so plates (capacitor) can store more charge increases capacitance and amount of Energy (U) stored in the capacitor

dielectric | dielectric constant = k

components in a row (i.e. train cars) | any two components not separated by a node

components in series

single components in alternate paths connecting the same nodes

components in parallel

Equation: Resistors in Series

R(eq) = R1 + R2 + R3.......

Equation: Resistors in Parallel

R(eq) = 1/R1 + 1/R2 + 1/R3......

Equation: Capacitors in Series

C(eq) = 1/C1 + 1/C2 + 1/C3...

Equation: Capacitors in Parallel

C(eq) = C1 + C2 + C3...

Electric and mechanical are the SAME used to integrate electricity and mechanics into the same question Ex: Given V & I of a machine, how quickly can it life a mass (m) to height (h)?

Power

Set electric power = to mechanical power only when _____

energy is dissipated as heat by a resistor

Equation: Power w/ current and voltage

P = I * V

Equation: Power w/ current and resistance

P = I^2 * R

Equation: Power w/ voltage and resistance

P = V^2 / R

rate at which heat is generated as current goes through a resistor

power dissipated

net movement of electrons is unidirectional in a circuit

direct current (dc)

The movement of _______ creates power

electrons

current created by oscillating electrons back and forth in simple harmonic motion; voltage or current described by sine wave

alternating current (ac)

Max current occuren when electrons are at their max ______

voltage

Equation: Max Voltage

V(max) = √2 * V(rms)

Equation: V(rms)

V(rms) = V(max) / √2

Equation: I(rms)

I(rms) = I(max) / √2

field created by changing electric field; created by moving charge or current; has N and S pole; like poles repel represented by force lines that point from the north pole to the south pole

magnetic field (B)

magnetic strength follows inverse square rule except in ______

long straight wire

Equation: Force on a charge moving through a magnetic field w/ velocity

F = q * v * B * sin(ø) | Note: ø = angle between magnetic field and velocity of the charge

Force is ______ to Velocity and the Magnetic Field

perpendicular

Since a force due magnetic field perpendicular to velocity, it does no ______

work

Magnetic Force changes the ______ but never the _____.

direction but never the magnitude

a changing magnetic field creates an _____. This process is non-conservative because mechanical energy is transferred into heat energy

electric field

Equation: circular path of charged particle through a magnetic field

q * V * B = m * (v^2 / r)

sin(90) = ?

= 1

cos(90) = ?

= 0

a moving charge experiences force when moving through a _______

magnetic field

a magnetic field is generated by ________

a moving charge

Equation: find circular path of a charged particle through a magnetic field

2 * pi (3.14) * r | Note: r = radius of circle

Equation: Magnetic Force

F = q * v * B