Download PHYSICS II - REVIEW SHEET 1

PHYSICS II – Equations: Exam2
CAPACITORS:
a) C = Q / V Capacitance (units = C/V = farad)
b) C = (o A)/d (parallel plate capacitor)
c) C = (2oL)/ln(rb/ra) (cylindrical capacitor)
d) U = Q2/(2 C) = (Q V)/2 =(C V2)/2 (Energy stored in capacitor)
e) UE = (o E2)/2 (Energy density of an Electric field)
f) Ceq = C1 + C2 + C3 + (parallel) g) 1/Ceq = 1/C1 + 1/C2 + 1/C3 + (series)
DIELECTRICS/DIELECTIC CONSTANT:
a) K = dielectric constant (electric field in vacuum/electric field in dielectric)
b) Electric field and potential in a dielectric material: replace k by (k/K) or o by ( oK)
ELECTRIC CURRENTS:
a) I = Q/t (units = Coulomb/Sec = Ampere) b) V = I * R (Ohm's Law)
c) R =  L/A (= resistivity) d) P = I * V = I2* R = V2/R (Power dissipated)
e) Req = R1 + R2 + R3 + (series) f) 1/Req = 1/R1 + 1/R2 + 1/R3 + (parallel)
g) Kirchhoff's Rule:  emf’s =  VD (any loop)  Iin =  Iout (any junction)
h) Current density J = I/A (A/m2) i) J = nev (n = # carriers/volume; e = charge . V =drift
velocity) j) E = ρ J ( ρ is the resitivity)
MAGNETIC FIELD EFFECTS
a) Magnetic Field Intensity: B (tesla or webers/m2)
b) Magnetic Force on Charge: F = q(v x B) = qvB sin  (right hand rule)
c) Magnetic Force on Current: F = I(L x B) = ILB sin (right hand rule) dF = I(dl x B)=
IdlBsin
d) Magnetic Torque on Loop: = I(A x B) = IAB sin  (right hand rule)
Magnetic Moment: = IA ;  =  x B = B sin 
.
Magnetic Energy U = - B = -Bcos 
e) Motion of a charged particle in magnetic field perpendicular to velocity:
Magnetic Force = Centripetal Force: qvB sin 90 = mv2/r ; (qvB sin  = mv2/r) general
mass spectrometer (velocity selector: qvB = qE ==> v = E/B)
RC CIRCUITS:
charging: I = (/R)e-t/RC: Q = (C * )(1-e-t/RC): Vcap =  (1-e-t/RC)
discharge: I = - (Vmax/R)e-t/RC: Q =(Qmax)e-t/RC: Vcap = (Vmax)e-t/RC
-----------------------------------------------------------------------------------------------------------permittivity of free space : o = 8.85 x 10 -12 C2/N M2