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49 Cards in this Set
- Front
- Back
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Electrostatic force |
F = k * (|q1|*|q2| \ r²) |
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Quantization of charge |
q = n * e (must be a multiple of the elementary charge) |
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Electrostatic force related to efield |
F = q * E = m * a where there is a force, there's an acceleration |
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Coulomb's Law |
Force depends on the product of the charges involved |
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Electric field |
E = F / q₀ = k * (q /r²) q₀ is a positive test charge |
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Electric field, dipole |
E = (1/ 2π∈₀) (p / z³) p = qd (dipole moment z = distance from center to point |
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Torque on a dipole |
T = p × E (maximized when perpendicular) |
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Potential energy of a dipole |
U = - p · E (maximized when parallel) |
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Electric field, charged disk |
E = (sigma / 2∈₀) * ( 1 - ( z²/√(z²+R²)))
z = distance along axis from center of disk R = radius of disk
sigma= surface charge density |
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Gauss' law |
∈₀ ∅ = qenclosed ∅ = ∫ E · dA
∅ = flux |
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Electric field, (infinite) sheet of charge |
E = (sigma) / (2∈₀) |
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Electric field, line of charge |
E = λ / 4π∈⁰r |
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Electric field, sphere of charge |
E = (q / 4π∈₀R³) * r |
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dipole moment (p) |
distance × |charge| |
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linear charge density λ |
charge per unit length |
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surface charge density (sigma) |
charge per unit area |
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Finding V from Efield |
∆V = - E ∆x ∆x = distance between two equipotential lines |
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Work and electric potential |
W = - U = - q V |
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Potential energy and electric potential |
U = q V |
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Kinetic energy and electric potential |
∆K = - q V |
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Potential, point charge |
V = 1 / (4 π∈₀) * (q / r) |
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Potential, dipole |
V = (k) * (p cosθ) / r²
r>>d (distance of dipole moment) |
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Potential, continuous distribution |
V = (k) ∫ dq / r |
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Capacitance |
C = q / V |
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Capacitance, parallel plate capacitor |
C = (A/d) ∈₀ |
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Capacitance, isolated sphere |
C = 4 π∈₀R |
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Capacitors, in series |
inverse (Csum) = inverse (Ceq) |
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Capacitors, in parallel |
Csum = Ceq |
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Potential Energy of a capacitor |
U = 1/2 CV² |
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Energy density, u |
(potential energy per unit volume)
u = 1/2 ∈₀ E²
where E is magnetic field magnitude |
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Dielectric |
To change calculations, multiply κ by ∈₀ |
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What is the dielectric? |
It is a conducting insulator that can be polarized with an applied magnetic field. Certain materials have dampening effects proportional to their composition on the electric field within that material. |
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Current density (J) |
= J; related to current by
i = ∫ J · dA |
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Current density, related to drift velocity |
J = (ne) * v_d
v_d = drift speed ; n = charge carrier density; J has same direction of particles if (+) and opposite if they are (-)
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Resistivity (rho) related to conductivity (sigma) |
rho = 1 / sigma = E / J
E = magnitude of E field |
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∆Resistivity can be approximated how? |
(rho_initial) * α (∆Temperature)
α = coefficient of resistivity |
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Electric power |
P = i * V = (current) * (electric potential) |
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Resistive dissipation |
P = i² R |
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Emf, definition |
dW / dq
Work per unit charge, units = volts |
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Ideal emf |
lacks any internal resistance. |
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Current, in terms of emf |
emf / (R + r)
little r is internal resistance |
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Rate at which chemical energy in Emf changes |
P_emf = i * Emf |
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Resistance, in series |
R_eq = R_sum |
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Resistance, in parallel |
(1/R_eq) = (1/R_sum) |
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Current while charging |
i = dq / dt = (Emf / R) e ^ (-t/RC)
exponential e, not elementary charge |
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Current while decharging |
i = dq / dt = (-q_initial/RC) * e ^ (-t/RC) |
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To charge by conduction: |
a conducting, charged object is touched to another object |
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To charge by induction: |
Bring a charged object near another object that is grounded (i.e. Electrostatic discharge) |
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Positive charge is induced by |
Electrons leaving the newly charged object |
