Fe = ke\ q1\ q2/r2 ke = columb constant

V = U/q0 ΔV = ΔU/q0 = - ∫ E·ds

1/Ctot = 1/C1 + 1/C2 + 1/C3 ....

E&M Flashcards by phoebe Stierhoff

Columb’s law

F_e = k_e*|q₁|*|q₂|/r²

k_e = columb constant

How well did you know this?

Not at all

Perfectly

Columb’s constant

k_e = 1/(4*π*ϵ₀)

How well did you know this?

Not at all

Perfectly

Force of Electrical feild

F_e=qE

force that acts on a point charge

How well did you know this?

Not at all

Perfectly

direction of electrical field lines

positive charge to negative charge

How well did you know this?

Not at all

Perfectly

acceleration of particle in uniform electrical field

a = qE/m

How well did you know this?

Not at all

Perfectly

Electric Flux

Φ_E = EAcos(θ)

θ = angle between direction electrical field and normal of area

How well did you know this?

Not at all

Perfectly

Gaussian surface

closed surface containing charge

How well did you know this?

Not at all

Perfectly

Net flux through gaussian surface

Φ_E = E∮dA = q/ϵ₀

How well did you know this?

Not at all

Perfectly

potential energy of electric feild

ΔU = -q₀ ∫ Eds

How well did you know this?

Not at all

Perfectly

Electric potential

V = U/q₀

ΔV = ΔU/q₀ = - ∫ E·ds

How well did you know this?

Not at all

Perfectly

Work done on charge in electric field

W = qΔV

How well did you know this?

Not at all

Perfectly

Electric potential in uniform electric field
*how does electric field increase/decrease?*

ΔV = -Ed

electric field lines point in direction of decreasing electric potential

How well did you know this?

Not at all

Perfectly

electric potential from point charge

V = k_e*q/r

How well did you know this?

Not at all

Perfectly

relationship between equipotential surfaces and electric field lines

equipotential surfaces must be perpendicular to electric field lines

How well did you know this?

Not at all

Perfectly

electric potential due to continuous charge distribution

V = k_e ∫dq/r

How well did you know this?

Not at all

Perfectly

electric potential at surface of charged coductor

every point on surface of charged cuductor is at the same electric potential

How well did you know this?

Not at all

Perfectly

Electric field within charged conductor

electric field inside cavity must be 0

How well did you know this?

Not at all

Perfectly

Capacitence definition

C = Q/ΔV

How well did you know this?

Not at all

Perfectly

Capicitence of a charged sphere

Q/ΔV = Q/(k_eQ/R) = R/k_e = 4πϵ₀R

How well did you know this?

Not at all

Perfectly

Capicitance of parallel-plate capacitor

C = ϵ₀A/d

How well did you know this?

Not at all

Perfectly

Capacitors in parallel

C_tot = C₁ + C₂ + C₃ …

How well did you know this?

Not at all

Perfectly

Capacitors in series

1/C_tot = 1/C₁ + 1/C₂ + 1/C₃ ….

How well did you know this?

Not at all

Perfectly

Energy stored in capacitor

U = Q²/2C = 1/2*QΔV = 1/2*C(ΔV)²

How well did you know this?

Not at all

Perfectly

Energy density

u_E = U/Ad

How well did you know this?

Not at all

Perfectly

Capacitance with dielectric

C = ϰC₀

Voltage with dielectric

V = ϰV₀ *note: if voltage source is not turned off when dielectric is inserted, voltage will remain the same*

Definition of current

I = ΔQ/Δt

Current density

J = I/A = nqv_d J = σE *σ -\> is the coductivity of the conductor. (Ohm's law)*

Definition of resistance

R = ΔV/I

resistivity

ρ = 1/σ R = ρ\*l/A

temperature coeffecient of resistivity

α = (1/ρ0)\*(Δρ/ΔT)

resistance at temperature

R = R₀[1+α(T - T₀)]

Power in resister

P = IΔV P = I²R P = (ΔV)²/R

Voltage in battery

ΔV = ε - Ir *ε -\> emf (max possible voltage battery can provide between terminals) r -\> internal resistance of battery*

Resistors in series

R_tot = R₁ + R₂ + R₃ ...

Resistors in Parallel

1/R_tot = 1/R₁ + 1/R₂ + 1/R₃ ...

Kirchof's rules

1) Junction rule: sum of currents entering any junction in a circuit must equal the sume of the curents leaving that junction 2) Loop rule: The sum of potential differences across all elements around any closed loop circuit must be 0

RC circuit, using loop

ε - q/C - IR = 0 *ε -\> voltage on battery*

Initial current of RC circuit

I₀ = ε/R

maximum charge on capacitor in RC circuit

Q = Cε

charge as a function of time in charging RC circuit

q(t) = Cε(1 - e^-[t/RC]) = Q(1 - e^-[t/RC])

current as a function of time in charging RC circuit

I(t) = (ε/R)e^-t/RC

charge as a function of time for discharging capacitor in RC circuit

q(t) = Qe^-t/RC

current as a function of time for discharging RC circuit

I(t) = -(Q/RC)e^-t/RC

Galvanometer

* measures current and voltage * uses torque of magnetic field generated from coil * connect in series to measure voltage * connect in parallel to measure current

Ammeter

* measures current * should ideally have 0 resistance * connect in series

Voltmeter

* measures voltage * ideally has infinite resistance * connect in parallel

direction of magnetic field lines

north to south

force on charged particle in magnetic field

**F**_B = q**v** x **B** = |q|vBsinθ θ -\> angle between v and B

Magnetic force on current carrying wire

**F**_B = I**L**x**B**

symbol for magnetic feild out of page

•

symbol for magnetic field into page

Right hand rule

![]()

magnetic force from closed current carrying loop in magnetic field

F_B = 0

magnetic force on curved current carrying wire

equal to a straight wire connected to end points carrying the same current

maximum torque on current carrying loop in magnetic field

τ_max = IAB

torque of current carrying wire in magnetic field

τ = IAxB = IABsinθ *θ -\> angle of magnetic field B and normal of area*

radius of motion of charged particle in magnetic field

r = mv/qB

velocity selector for electric and magnetic field

qE = qvB v = E/B

Biot-Savart law

d**B** = [μ₀/4π][I\*d**s** x **r**/r²]

magnetic field from current in infinite long wire

B = μ₀I/2πr

magnetic force between 2 parallel wires

F_b/L = μ₀I₁I₂/2πa

Ampere's law

∮**B**•d**s** = μ₀I

magnetic field inside radius of conductor

B = (μ₀I/2πR²)r | (linear)

magnetic field of solenoid

B = μ₀(N/L)I = μ₀nI * N -\> numer of turns* * L -\> length* * n -\> N/L*

Magnetic flux

Φ_B = BAcosθ

Gauss's law for magnetism

∮BdA = 0 magnetic flux through a closed surface is always 0

Faraday's law of induction

V = -dΦ_B/dt

direction of current from enduced emf (lenz's law)

magnetic field from current must oppose the change of magnetic field from the magnet

emf for AC generator

ε = NABωsin(ωt)

Maxwell's equations

∮EdA = q/ε₀ ∮BdA = 0 ∮Eds = -dΦ_B/dt ∮Bds = μ₀I +μ₀ε₀dΦ_E/dt

self induced emf in inductor

ε_L = -LdI/dt

Kirchof Loop for RL circuit

ε - IR - LdI/dt = 0

current in RL circuit

I = ε/R(1 - e^-[Rt/L])

Energy stored in inductor

U = (1/2)LI²

Total energy stored in LC circuit

U = U_C + U_L = Q²/2C + (1/2)LI²

charge as function of time for LC circuit

Q = Q_maxcos(ωt + φ)

Current as a function of time for LC circuit

I = ωQ_maxsin(ωt + φ)

Electric field from continuous charge distribution

E = k_e\*Int(dq/r²)

E&M Flashcards

(79 cards)