Table of Formulas and Constants * Physics 102
I. Electricity
Charge (q) on an electron(-) and proton (+) = 1.6 x 10 -19 Coulombs
1 Coulomb = 6.25 x 1018 electrons
Electrostatic constant k = 9 x 109 N∙m2/C2
Electrical permittivity of free space
F = k q1∙q2/r2 ΣF = ma
ϵo = 8.85 x 10-12 C2 /N∙ m2
k = 1/4Πϵo
a = Δv/t
V = Energy/ charge
Electric Field Strength = F/q = V/r
Capacitance C = K ϵo A/d = Q/V wjhere K is a dielectric constant for an insulating material
Energy = Work = Fxd = mgh = ½mv2
= ½ CV2 = ½ QV
Current I = q/t
Resistance R = V/I = ρL/A
Ohms Law: V = IR
V=E
-iR
Power (P) = VI = Energy/time
P= VI = W/t = I2R = V2/R
Series Circuits:
Parallel Circuits:
1/C total = 1/C1 + 1/C2 + 1/C3……
C total = C1 + C2 + C3……
R total = R1 + R2 + R3 + …….
1/R total = 1/R1 + 1/R2 + 1/R3 + …….
V total = V1 + V2 + V3……
V total = V1 = V2 = V3 = ……
I total = I1 = I2 = I3 =…..
I total = I1 + I2 + I3…..
Units: force = Newtons = kg m/s2
Power = Watts = Joules/sec
Energy = Nm or Joule
1 electron-volt = 1.6 x 10-19 Joules
II. Magnetism
B = Φ/A
Fmagnetic = qv x B =ILxB
E= Blv
E= - n ∆Φ/∆t
Magnetic permeability of free space
μo = 4π x 10-7
T∙m/A
Hand Rules
Cross product AxB = A B sinθ in magnitude
and the right hand rule tells its direction. For any mathematical
system….
. For specific magnetic
situations, see the pictures below.
Magnetism in wires; Left
hand rules for are electron flow (negative
current). Positive charges (and conventional current) obey right hand rules.
Particle Shot Through a Field:
Thumb with the way the electrons go
(current), Fingers with field, Palm
will show the direction of the force on
the particle or wire.
Straight wires:
Loops & Coils:
Thumb with current,
Fingers with current,
fingers curl in the direction
thumb points North in the
of the B field.
direction of the B field.
IV.
AC Circuits
L = inductance C = capacitance f= frequency V= voltage I = current
RMS = root mean square
R = resistance
ω = angular frequency
Summary of the properties of circuit elements.
Resistor
Capacitor
Inductor
units
symbol
relation
power dissipated
energy stored
ohm, Ω = V / A
R
V=IR
P = I V = I² R
= V² / R
0
Irms 
farad, F = C / V
C
Q=CV
henry, H = V s / A
L
emf = -L (∆I / ∆t)
0
0
PEC = C V² / 2
PEL = L I² / 2
ω = 2 π f = 1 /√LC
Imax
 0.707 Imax
2
Inductive reactance XL = 2 f L
Capacitive Reactance Xc = 1/ (2π f C)
V. Waves
V= f λ
Focus = C/2
n1 sin θ1 = n2 sin θ2
θcritical = sin-1(1/n)