Equations Flashcards
Half life
n=noe^-(wavelength)(time)
n=no(1/2)^t/h
Electric field equation
E=Fe/q
E=kQ/r^2
Finding Electric field with voltage
V=Ed
Wave formula for velocity
v=f(wavelength)
Speed of light
c=3 x 10^8 m/s
Period and frequency relation
f=1/T
Electric force
qE
Capacitators in series
Add in reciprocal
Electric field between anode and cathode
E=(V-IR)/L
Capacitance is proportional to
Plate area
Ohm’s Law
I=V/R
Voltage, resistance, current
V=IR
Increase in decibel by 20
Increase in sound level by 100
Coulomb’s law
Fe=kq1q2/r^2
Coulomb’s constant/electrostatic constant/k
8.99 x 10^9 Nm^2/C^2
1/4(pi)eo
Permittivity of free space/e0
8.85 x 10^-12 C^2/Nm^2
Electric field equations
E=Fc/q=kQ/r^2
E in N/C or v/
Electric force within an electric field
Fe=qE
Electrical potential energy
U=kQq/r
Electrical potential
V=U/q
In Volts= J/C
Electrical potential without the test charge
V=kQ/r
Voltage/Potential Difference
DeltaV=Va-Vb=Wab/q
Other equations for electrical potential energy (U)
U=q x DeltaV
U=qEd
Dipole electrical potential
V=kqdcos/r^2
d=distance between two charges
r= distance between dipole center & a single point
Dipole moment (p)
p=qd
Magnitude of the electric field on the perpendicular bisector of the dipole
E=1/4(pi)eo x p/r^3
Net torque on a dipole
t=pEsin
Electric potential between two plates
V=Ed
uo/permitivity of free space
4(pi) x 10^-7 Tm/A
Magnetic field on a straight, current carrying wire
B=uo(I)/2pi(r)
Magnetic field at the center of a circular loop of wire
B=uo(l)/2r
Magnetic force
FB=qvBsin
Magnetic force created by a current carrying wire
FB=ILBsin
Theta is angle between L& B
Electric field between 2 plates
E=V/d = Q/eoA
Current
Q/Delta(t) in amperes (A=C/s)
Kirchhoff’s junction rule
Iin=Ileaving
Kirchhoff’s loop rule
V(source)=V(drop)
V is in J/C
Resistance equation
R=pL/A
in Ohms
SI unit of resistivity
Ohm meter
Ohm’s Law
V=IR
Actual voltage supplied by a cell
V=E(cell) - ir(int
E(cell)= emf of the cell
i=current through cell
rint=internal resistanceP
Power equations
P= W/t= Delta(E)/t
Power of a resistor
P= IV=I^2R=V^2/R
How is resistance & voltage drop in series treated?
Additive
How to find voltage drop across resistors?
Find current & then use V=IR equation to find voltage drops
How are resistance & voltages in parallel treated?
All voltages are equal
Resistance is reciprocal added
Resistance reduction when n identical resistors are wired in parallel
R/n
How to find current in parallel circuit
Find current through whole circuit & through each resistor using individual resistors
Capacitance
Q/V
in Farads=C/V
Parallel plate capacitance
C=eo(A/d)
Uniform electric field equation
E=V/d
Potential energy stored in a capacitor
U=1/2CV^2=1/2QV=1/2Q^2/C
Capacitance due to a dielectric material
C’=kC
What happens to capacitators in series
Decrease capacitance
Reciprocal addition
Total voltage is sum of all individual voltages
What happens to capacitators in parallel?
Addition of all capacitators
Voltages all equal in each capacitator to the source
Propagation of a wave equation
v=f(wavelength)
Period
1/f
Number of seconds per cycle
Angular frequency
=2(pi)f=2(pi)/T
Speed of light
c=3 x 10^8
Speed equation
v=f(wavelength)
Law of refection
Angle 1 = Angle 2
f for all spherical mirrors
f=r/2
Relationship of focal length and distances
1/f=1/o + 1/i = 2/r
Magnification
m = -i/o
Snell’s law
n1sin1=n2sin2
Critical angle equation
Angle x=sin^-1 (n2/n1)
Lensmaker’s equation
1/f=(n-1)(1/r1-1/r2)
Power
P=1/f
in diopters
Multiple lens focal lengths
1/f=1/f1 + 1/f2 + 1/f3…
Equivalent power of multiple lenses
P=P1 + P2 + P3…
Magnification of multiple lenses
m=m1 x m2 x m3
Location of dark fringes
asin=n(wavelength)
Equation for double slit dark fringe position
dsin=(n +1/2)(wavelength)
d=distance between 2 slits)
Energy of a photon
E=hf
h=Planck’s constant (6.626 x 10^-34 Js)
E=energy of a photon
Maximum kinetic energy of the ejected electron
Kmax=hf-W
W=Work function of the metal
Work function
Minimum energy required to eject electron
W=hfT
Mass defect equation
E=mc^2
Rate of nuclear decay
= -constant (n)
Exponential decay
n=noe^-(constant) (t)
decay constant
0.692/half life