All Equations (inc Formula Booklet - currently not indicated) Flashcards
*Hooke’s Law (F)
F = kx
force = spring constant * extension
Newtons, N
*Hooke’s Law (E)
E = ¹/₂Fx = ¹/₂kx^2
elastic energy = ¹/₂ * force * extension
elastic energy = ¹/₂ * spring constant * extension^2
Joules, J
Multiple springs in parallel
K(total) = K(1) + K(2) + K(3) …
Multiple springs in series
1/K(total) = 1/K(1) + 1/K(2) + 1/K(3) …
*Stress
σ = F / A
Stress = Force/Area
Pascals, Pa OR Nm^-2
*Strain
ε = x/L
Strain = Extension/Original Length
No units, A ratio
*Young Modulus
E = σ/ε = (FL)/(Ax)
Young Modulus = Stress/Strain
Pascals, Pa OR Nm^-2
Tensile Strength
Tensile Strength = Breaking Force/Cross-sectional Area
Pascals, Pa OR Nm^-2
Fracture Energy
Fracture Energy = energy needed to break/Cross-Sectional Area
Jm^-2
Relation between Drift Velocity and Current
I = nAev
I = Current
n = number of charge carriers
A = Cross-Sectional Area
e = charge on charge carrier
v = drift velocity
Amps, A
Lens Power
Lens Power = 1/f
Lens Power = 1/focal length
Dioptres, D
Curvature of a Wave
Curvature of a Wave = 1/r
Curvature of a Wave = 1/radius of wave
Curvature of a wave leaving a Lens
= Curvature of wave entering + Curvature added by the Lens
*1/v
1/v = 1/u + 1/f
v = image distance (+ve)
u = object distance (-ve)
n.b. derived from 1/f = 1/v + (- 1/u)
metres, m
Magnification
M = v/u = image size/object size
Ratio, no unit
*Shannon’s Criteria
b = log2 (V(total)/V(noise))
V(total) = total range of data
Transmission Rate
Transmission Rate = total info sent / time taken
Charge
Q = nq
Charge = number of electrons * charge on one electron
Coulomb, C
*Current
I = Q/t
Current = charge / time
Ampere, A
*Potential Difference (Volts)
V = W/Q
Volt, V
Resistance
R = V/I (or V=IR)
Ohm, Ω
Conductance
G = 1/R = I/V
Siemen, S
*Power
P = W/t = IV = I^2 * R = (V^2)/R = F*v
Watt, W
*Work Done
W = P/t = ItV = F*s
Work = Force * Displacement
Joules, J OR Nm OR kgm^2s^-2
*Resistance (wires)
R = ρL/A
L = length of wire
ρ = resistivity (Ωm)
A = Area
*Conductance (wires)
G = σA/L
L = length of wire
σ = conductivity
A = area
*Potential Divider equations
Vout = (R1/(R1+R2))*Vin
V1/V2 = R1/R2
where ε = Vin and the voltage recorded across R2 is Vout
*EMF
ε = V + I*r
EMF = terminal p.d + current * internal resistance
EMF off of graph
A graph of V against I (V = y-axis)
Frequency (wave)
f = 1/T
frequency = 1 / Time Period
Hertz, Hz or s^-1
Diffraction (grating)
nλ = dSinθ
n = order of maxima
θ = angle of separation (from n = 0)
d = distance between individual slits
λ = wavelength of source
Critical angle
Sin C = n2 / n1
C = critical angle
n2 = refractive index light is going into
n1 = refractive index light is leaving
Youngs Double Slit
nλ = (xd)/L
n = order of maxima
d = distance between individual slits
λ = wavelength of source
x = distance between the fringe (from n = 0)
L = distance between the slit and the ‘screen’ the fringes are projected on
*Capitance
C = Q/V
Capitance = Charge / Voltage
Farad, F
*Energy stored in a capacitor (some in booklet)
E = 1/2QV (= 1/2CV^2 = Q^2/(2*C))
The area under a pd charge graph (pd = y-axis)
Current (capacitor/capacitance)
I = Q / (R*C)
Current = Charge / (Resistance * Capitance)
*dQ/dt
dQ/dt = -Q/RC
rate of change of charge is proportional to charge remaining
Time Constant
Time Constant = R*C
Resistance * Capitance
RC = how long it takes for the charge to fall to 37% of its original value (e^-1)
Charge left on a capacitor
Q = Qo * e^(-t/RC)
Qo = Initial charge
t = time
RC = time constant
Current left on a capacitor
I = Io * e^(-t/RC)
Io = Initial current
t = time
RC = time constant
Potential Difference left on a capacitor
V = Vo * e^(-t/RC)
Vo = Initial pd
t = time
RC = time constant
Energy of a photon (general)
E = h*f
Energy = Planck’s constant * frequency
Energy gained by an electron (p-n junction)
E = q*V
q - electron charge
V - striking voltage
Momentum (de Broglie)
p = h/λ
momentum = Planck’s constant / wavelength
(can be linked with E = h*f)
SUVAT (only one not given)
s = 1/2t(u + v)
Momentum
ρ = m*v
kgms^-1