Everything Flashcards
added AC
4 kinematic formulas
v=u+at
v^2=u^2+2as
s=ut+1/2at^2
s=1/2(u+v)t
Fnet of falling bodies
Fnet=W-F
Formulas of force (both impulse and constant mass)
F=dp/dt
F=ma (constant mass)
Impulse
p=mv
Conservation of momentum
m1u = m1v1 + m2v2
Elastic collision
u1-u2=v2-v1
speed of approach=speed of separation
inelastic collision
m1v1 +m2u2 = (m1+m2)v
Moments
M=FxD
Clockwise moments= Anticlockwise moments
Hooke’s law
F=kx
Upthrust
U=pvg
Work done by force
WD=Fs cos θ
Work done ON gas
WD=-Pexternal (△v)
Work done BY gas
WD= Pexternal (△v)
Kinetic energy
KE=1/2mv^2
Gravitational potential energy
GPE=mgh
Elastic potential energy
EPE=1/2kx^2
Power
WD per unit time
P=Fv
Efficiency
useful WD/energy input x100%
Angular displacement θ
θ= s/r
Angular velocity ω
ω=dθ/dt
=2πf
=2π/T
Uniform circular motion v
v=rω
Centripetal acceleration Ac
Ac=v^2/r
=rω^2
Centripetal force Fc
Fc=mv^2/r
=mrω^2
Gravitational force of attraction between 2 masses
F= Gm1m2/r^2
(GRAV FIELD) Relationship between T and r?
T^2 ∝ r^3
Gravitational field strength g
g=Gm/r^2
Weight at poles of earth vs equator
At poles, W=N
At equator, Fc=W-N
Gravitational potential Φ
Φ=-Gm/r
Potential energy on mass in grav field
Ep=mΦ
Escape velocity and derivation
v=squareroot(2Gm/R)
derived from Ekinit=m△Φ
Energy needed for mass to reach infinity
TE=0
KE of orbiting mass
F between 2 masses= Fc
Gm1m2/r^2 = mv^2/r
Differences between in phase and out of phase? △Φ (phase diff)
in phase, △Φ=0
out of phase, △Φ=180 or π
Angular frequency θ
θ=2πf
=dθ/dt
Simple harmonic motion acceleration a
a=-ω^2x
Horizontal spring F
F=-kx
In a horizontal spring system what is ω?
ω=squareroot (K/m)
as a=-(K/m)x
In a pendulum, what is ω?
ω=squareroot (g/L)
as a=-(g/L)x
(graph) formulas for displacement, velocity and acceleration for Simple harmonic motion
x=x0 sin wt
v=wx0 cos wt
a=-w^2x0 sin wt
general velocity formula for SHM
±ω squareroot (x0^2-x^2)
KE of SHM displacement
KE=1/2mω^2 squareroot (x0^2-x^2)
PE of SHM displacement
PE=1/2mω^2 x^2
Graphical formula of PE energy-time graph
PE=1/2m(ω^2)(x^2)
Graphical formula of KE energy-time graph
KE=1/2m(ω^2)(x0^2-x^2)
Graphical formula of TE energy-time graph
TE=1/2m(ω^2)(x0^2)
Speed of EM waves
c=3.0 x 10^8
Intensity formula
and is proportional to??
I=Power/Area
I∝Amplitude^2
Power formula (intensity)
P= E/t
Malu’s Law (intensity/polarising)
I=I0 cos^2 θ
I∝cos^2 θ
Single slit diffraction formula
sin θ= λ/b
b is slit width
Rayleigh’s criterion (2 sources of light)
θ= λ/b =s/r
s is the dist between 2 sources
r is the dist between slit and source
Double slit
x= λD/a
x is fringe sep
a is slit sep
D is total dist from source to slit
Diffraction grating
d sin θ= n λ
d is slit sep
n is order
Fixed end vs free end (which one is in phase and which is antiphase)
Fixed end is in phase while free end is antiphase
Stationary waves 2 free end/fixed end formula for Length and frequency
L=n(λ/2)
F=n(V/2L)
Stationary waves 2 free end/fixed end formula for Length and frequency
L=n(λ/2)
F=n(V/2L)
Electric field strength E at a point in the field
E=F/Q
OR F=EQ
Electric field strength of uniformed field between charged parallel plates
Electric field strength of point charge in air
Electric force Fe
Fe= Eq
Coulomb’s law
Electric potential energy U
Positive and neg meaning
U=QV
Pos U: wd on field
Neg U: wd by field
Change in electric potential energy
△U=Q△V
=Q(Vf-Vi)
Electric potential due to point/sphere charge
Same as electric field strength of point charge but instead of r^2 its just r this time
Electrical potential energy of 2 isolated point charges
Electric potential of multiple point charges
Vtotal=V1+V2+V3
Electric potential energy of multiple point charges
Steps to curve sketching for Resultant electric potential graph and resultant electric field strength graph
- Find magnitude of changes
- Find location of 0 field strength when E=0
- Find potential at zero field strength
- Find field strength at surface of spheres
Graph eqn I of AC
I=I0 sinwt
Why does heat dissipate in ac?
- power dissipated in resistor
- P proportionate to current square because P=I2R
OR - ac current change direction every half cycle but direction is independent of current direction
Finding RMS value in AC
- Square function/graph
- Average value
- Square root avg value in 2
What is RMS value definition?
RMS of steady direct current dissipates thermal energy at the same avg rate as resistor as ac in a given resistor
AC Formula of 《I> vs Irms difference?
area/T = average current squareroot (squared area/T) =Irms
AC sinosoidal easier formula
Irms= I0/squareroot 2
Vrms=V0/squareroot 2
Power of ac circuits
Pavg=Irms Vrms
Pheat of AC
Pheat=I2Rcable
Explain EMI and transformer input
- B field generation
- Change
- Flux linkage
- Faraday’s law
Ideal transformer
Pinput=Poutput
Graph eqn of V om AC (for ac-dc rectification)
Vac=V0 sin wt
Equipotential lines definition
lines joining points in a field with same potential
ALWAYS meet electric field lines at right angles
(ie equipotential lines are perpendicular to electric field lines)
What happens when charge is moved along an equipotential line
no work is done
Relationship between electric field strength and electric potential
[MAG] electric field strength E is numerically equal to the electric potential gradient (dV/dr) at a point in the field
[DIR] neg sign shows direction of field strength, pointing to lower potential
Electric potential gradient
dV/dr
only add negative for E=-dV/dr, where direction is needed
Electric force using electric potential
F=-dqV/dr
=dU/dr
U=qV
Unknown temp for thermometric property of empirical centigrade scale
Absolute temp from celsius
K=C+273.15
Celsius to absolute temp
C=K-273.15
Ideal gas law for moles of gas
pV=nRT
Ideal gas law for particles of gas
pV=NkT
One mole
6.02 x 10^23
One mole of H atoms weigh 2g and 0.002kg
Explain/prove pV=⅓Nm (basic idea)
- change in momentum
- N2L, F on 1 particle
- N3L F on wall opposite to F on gas particle
- Average F over area for MANY collisions from many particles in a random distribution
Explain/prove pV=⅓Nm (LONG WORKING)
KE of gas particles
=3/2 kT
KE directly prop to T
Specific heat capacity C
c=Q/m△T
basically Q=mc△T
Specific latent heat L
L=Q/m
Internal energy of a gas U
U= KEsum + PEsum
Internal energy of an ideal gas U
Uideal= KEsum + 0
because PEsum is 0
or Uideal = N
= 3/2 NkT =3/2nRT =3/2pV
First law of thermodynamics
△Uincrease= Qto + Won
overall energy = heat + pressure
WD on gas
WDon = -Pext△V
Answering framework for thermodynamics and internal energy U
Microscopic vs Macroscopic
KE (temp)
PE (V, phase)
WD on p-V graphs
Area under graphs
p-1/V graph for isothermal?
linear graph of p=nRT(1/V)
Magnetic flux Φ (FOR AREA)
Φ= Bperpendicular A
= (B cos θ) A
= BA cos θ
Magnetic flux linkage (FOR SOLENOID COIL)
NΦ = N(BA)
= N(B cosθ)A
= NBA cosθ
Induced electromag induction at a particular point
Einduced= -d(NΦ)/dt
= -d(NBA cosθ)/dt
AVERAGE Induced electromag induction
Eave= △Φ/△t
Layman EMI vs EM
EMI: Kinetic to electrical
EM: Electrical to Kinetic
Explaining EMI induction framework
- Field
- Change/cut
- Linkage
- Faraday’s law
Explaining eddy currents and damping
- Explain why emf is induced in the disc
- Explain why eddy currents are induced
- Explain why the disc comes to rest after a few oscillations
Constant current I
I=Q/t
Q=It
Current definition and d?/d?
rate of flow of charge
dQ/dt
Drift velocity v for current carrying conductor
I =nAvq
Proving drift velocity formula
Potential difference pd
V=W/Q
Power supplied by source
P =ItotalE
=Itotal^2Rtotal
Power output of component
P=IdeviceV
=I^2Rdevice
Resistance
R=V/I
Resistance (the wire area etc)
R=pL/A
Terminal pd (internal resistance)
Vt= E - Ir
Efficiency
Eff= Pload/Psource
=I2Rload/I2Rtotal
=Rload/Rload+r
How to increase efficiency?
minimise internal R of source
OR
maximise R of component
Efficiency at max power
50% eff
Maximum power transfer theorem
Rext same as Rint of EMF source
Resistors in series
Reff= R1 + R2 + … +Rn
Resistors in parallel
1/Reff = 1/R1 + 1/R2 + … + 1/Rn
OR
Reff= RaRb/Ra+Rb
Potential divider rule
Vout/Vtotal = R/Rtotal
Potentiometer circuit formula
Vtapped/Vtotal = Ltapped/Ltotal = Rtapped/Rtotal
Balanced conditions of a potentiometer
VPJ=VQR
0=IPQ=IRJ
No current. Length of PJ is the balanced length
Mag flux density of a long straight wire
B=µI/2πd
Mag flux density of a flat circular coil
B=µNI/2r
N is no of turns PER UNIT LENGTH and NOT NO OF TURNS
Mag flux density of a lomg solarnoid
B=µnI
Mag force in a wire
F=BILsinθ
B is perpendicular!
F on 1 by 2= B2 I1 L1
Mag force of charge particle
F= BQv sinθ
Bev sinθ for electron!
F on charge moving in a circular field
equate Fb=Fc to get
Bqv sin 90=mv^2/r (find r)
or =mrw^2 (find T)
Magnetic field into vs from paper
Into: clockwise
From: anti-clockwise
Energy of 1 photon
E=hf
=hc/λ
Relation of energy of photon and wavelength
Energy decrease when wavelength increase
Photoelectric eqn
hf= Φ+½mvmax^2
eV to joules
1eV=1.6 x 10^-19
Threshold frequency
minimum freq for emission
hf=Φ
(basically the ½mv^2=0 and emitted e have no energy because energy is only for emission)
E is emitted when hf>Φ and ½mv2>0
Stopping potential quantum physics Vs
eVs= ½mvmax^2
Saturation current graph sketching
y axis (current i): ne/t Intensity of light proportional to rate of arrival n/t Intensity= Nhf/tA I=P/t =(Q/t)(1/A) =(nE/t)(1/A)
X axis (Voltage V): hf=Φ+½mv^2
X axis intersect: KEmax= eVs
Deexcitation and excitation of electron
Excitation: hf=|Ef-Ei|
absorption spectra, photon is absorbed during upgrade
Deexcitation hf=Ef-Ei
emission spectra, photon is emitted during downgrade
Answering the spectra qns for quantum
- Define spectrum
- atom and photon movements, energy levels
- emit/absorb
- transit energy direction
- resultant observation
2 components of ouput Xray spectrum
- characteristic peaks
- broad continuous bg
KE loss=Ephoton
qeV=hf=hc/λmin
Wavelength for particle (wave-particle duality)
when momentum is given
λ =h/p
=h/mv
Heisenburg uncertainty principle
△p△x > h
MUST BE IN THE SAME DIMENSION
Nuclear binding energy
E=△mc2
=(total rest mass of reactants-total rest mass of products) c2
energy released in a nuclear reaction
total binding energy of products–total binding energy of reaction
= (total rest mass of reactants-total rest mass of products) c^2
Charges of alpha beta gamma
A +2e
B -e
Gamma 0
Ioinising power of alpha beta gamma
A strong (larger mass, more charge)
B moderate
Gamma weak
penetrating power of alpha beta gamma
A low
B medium
Gamma high
Nuclear eqn of alpha beta gamma
A gives out 42H
B gives out 0-1e
Gamma gives out y with unchanged original reactant
Activity of radioactive decay/rate
A=λN
A= -dN/dt
λ decay constant and A the rate of decay
half life t½
t½+ ln 2/λ
N=N0(½)n
N/N0= A/A0 = e-λt