Download Table of Formulas and Constants * Physics 102

A.P. E&M C * Mega Magnetism Summary
I. Hand Rules
Cross product AxB = A B sinθ in magnitude
and the right hand rule tells its direction.
Magnetism in wires; Left
hand rules for are electron flow (negative current).
Positive charges (and conventional current) obey right hand rules.
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.
II. Forces on Wires & Charges
For wires in B-field
Fmagnetic = =
I LxB
For charges shot through a B-field.
qv x B = Fcentripetal = mv2/r
Set the above 2 equal to each other to analyze charged particles
trapped in circular orbits by magnetic field.
III. Calculating B-Fields in Various Situations
B = Φ/A
B inside long coil =
B straight wire =
μo I or nμo I
B center of a single loop =
Magnetic permeability of free space
μo = 4π x 10-7
T∙m/A
Units: magnetic flux Φ in Webers. Magnetic field strength B in Teslas or Wb/m 2.
a. Flux using integration in 2-D
b. Gauss' Law for Magnetism (integration in 3-D)
c. Biot-Savaart Law: to find any field from any current anywhere
d. Ampere's Law
IV. Induction
Faraday's Law
E= B v
For moving a wire through a
B-field to generate current
Lenz's Law
E= - n ∆Φ/∆t
For moving a magnet in or out of a coil or turning a field on or off
IV.
AC Circuits
L = inductance C = capacitance f= frequency V= voltage I = current
R = resistance
Z = impedance
X = reactance
ω = angular frequency
Note: oscillating circuits appear on the AP, but they never have an AC Generator in a circuit problem. Material in red
on this page will not be on the AP exam, though it is widely taught and appears on the SAT2 in Physics
=
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 
Imax
2
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
 0.707 Imax
Inductive reactance XL = 2 f L
ω = 2 π f = 1 /√LC
Capacitive Reactance Xc = 1/ (2π f C)
This
AC
theory
will
not
be
on
the
AP
exam
V. RLC Direct Current Circuits
Opening and closing circuits:
Oscillating RLC Circuits
Starting with a capacitor C charged at 1 Volt connected to an inductor L,
current grows as capacitor discharges….
…storing magnetic energy in the field (
as the capacitors electric field loses energy ( ½ CV2).