VCE unit 3 and 4 physics cheat sheet PDF

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physics cheat sheet...

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The induced EMF of moving conductor in magnetic field

Peak, Peak-Peak&RMS

Waves

A conductor initial in magnetic field doesn’t have induced current because no change in magnetic flux. However, when it starts moving magnetic flux increase significantly, then doesn’t change and then slightly decrease until 0.

Root mean square voltage is the equivalent steady voltage DC supply which provide the same power

Transverse wave: oscillations are perpendicular to wave direction(light) Longitudinal wave: oscillations are parallel to the wave direction (sound)

𝜺 = 𝑩𝒍𝒗 𝜀: induced emf (V) B: magnetic field strength (T) l: length of conductor v: velocity of conductor

Faraday’s Law of induction Doesn’t matter whether the coil or magnet are changed if it is a change in magnetic flux there is induced EMF. Farday states if the flux through “N” number of loops of a coil changes from 𝜙𝑖𝑛𝑡𝑖𝑎𝑙 to 𝜙𝑓𝑖𝑛𝑎𝑙 then induced EMF/current. 𝜺 = −𝑵

𝚫𝝓 𝚫𝒕

= −𝑵

𝝓𝒇𝒊𝒏𝒂𝒍 −𝝓𝒊𝒏𝒕𝒊𝒂𝒍 𝒕𝒇𝒊𝒏𝒂𝒍 −𝒕𝒊𝒏𝒊𝒕𝒂𝒍

N: number of loops/turns

If the ends of a coil are connected to circuit, then a current will flow: Tips: negative sign indicate anticlockwise direction of 𝜀 induced current. 𝐼= 𝑡 1. Δ𝜙 = −; 𝜙𝑓𝑖𝑛𝑎𝑙 < 𝜙𝑖𝑛𝑡𝑖𝑎𝑙 : clockwise : 𝜀 = + 2.

Δ𝜙 = +; 𝜙𝑓𝑖𝑛𝑎𝑙 > 𝜙𝑖𝑛𝑡𝑖𝑎𝑙 : anticlockwise 𝜀 = −

Lenz’s Law 1. Don’t confuse induced current and induced current action. 2. When induced current action (magnet) try to move in/move out a coil or solenoid. Initially coil or solenoid don’t have induced current but because of induced current action this will generate induced current in coil or solenoid. The direction of this induced current will oppose direction of induced current action

𝑉𝑟𝑚𝑠 =

𝑣𝑝𝑒𝑎𝑘

𝐼𝑟𝑚𝑠 =

Graphs:

√2 𝐼𝑝𝑒𝑎𝑘

√2 𝑉𝑝𝑒𝑎𝑘−𝑝𝑒𝑎𝑘 = 2𝑉𝑝𝑒𝑎𝑘 1 𝑃𝑟𝑚𝑠 = 𝐼𝑟𝑚𝑠 𝑉𝑟𝑚𝑠 = 𝑣𝑝𝑒𝑎𝑘 𝐼𝑝𝑒𝑎𝑘 2 𝑃𝑝𝑒𝑎𝑘 = 2𝐼𝑟𝑚𝑠 𝑉𝑟𝑚𝑠 Factors: speed voltage f  period speed voltage f period

Transformers

Doppler efect

Application of electromagnetic induction, metal core increase efficiently. Size is independent. Only work for AC voltages.

Doppler effect is produced when the source of a wave moves with respect to the observed causing an apparent shift in frequency for the observer Relative motion Toward frequency  

𝑁𝑝 𝑉𝑝 𝐼𝑠 = = 𝑉𝑠 𝐼𝑝 𝑁𝑠

𝑁𝑠 > 𝑁𝑝 =Step up 𝑁𝑠 < 𝑁𝑝 =Step down Factors 𝑁𝑝  by X factor

Relative motion away frequency  

ONE CLOSED END&ONE OPEN END (Start: Node; End: Antinode) 𝟒𝒍 𝟒𝒍 𝝀𝒏 = = 𝒏 𝟐𝒂 − 𝟏 𝒏𝒗 (𝟐𝒂 − 𝟏 )𝒗 = 𝒏𝒇𝟏 𝒇𝒏 = = 𝟒𝒍 𝟒𝒍 n: number of harmonic (odd number only) a: number of antinodes l: length of string TWO CLOSED ENDS (Start&end: Nodes) 𝟐𝒍 𝝀𝒃 = 𝒃 𝒃𝒗 𝒇𝒃 = = 𝒃𝒇𝟏 𝟐𝒍 b: number of antinodes and number of harmonics TWO OPEN ENDS (Start&end: antinode) 𝟐𝒍 𝝀𝒄 = 𝒄 𝒄𝒗 𝒇𝒄 = = 𝒄𝒇𝟏 𝟐𝒍 c: number of nodes 𝑓1 : frequency of first harmonic

Diffraction of Wave

𝝀

Number of diffractions =𝑤 ; 𝑤 ≥ 1: 𝝀

𝐼𝑝 will  by X factor

The direction of induced current by changing area 1.

2.

For a magnetic field get into a page When S.A B:out of page Anticlockwise When S.A B: into the page Clockwise For a magnetic field go out page When S.A B: into the page Clockwise When S.A B: out of page Anticlockwise

AC Generator/Alternator •

•

Main different is slip ring: allow the coil rotating without tangling. Produce AC voltages which can be either positive or negative NOTE: GRAPH of EMF is NEGATIVE DERIVATIVE of magnetic flux

Transmission Loss

𝑃𝑖𝑛 𝑉𝑖𝑛 𝑉 𝑙𝑜𝑠𝑠 = 𝐼 𝑤𝑖𝑟𝑒𝑠 𝑅 𝑤𝑖𝑟𝑒𝑠 𝑉 𝑜𝑢𝑡 = 𝑉𝑖𝑛 − 𝑉 𝑙𝑜𝑠𝑠 2 𝑃𝐿𝑜𝑠𝑠 = 𝐼𝑤𝑖𝑟𝑒𝑠 𝑅 𝑤𝑖𝑟𝑒𝑠 𝑃 𝑜𝑢𝑡 = 𝑃𝑖𝑛 − 𝑃 𝑙𝑜𝑠𝑠 𝑃 𝑜𝑢𝑡 = 𝑉𝑜𝑢𝑡 − 𝐼 𝐼 𝑤𝑖𝑟𝑒𝑠 =

Transformer allow same power to transmitted at higher voltage, higher voltage lower current, lower current means lower power losses in transmissions.

Average EMF Negative derivative of sin(x) is cos(x) and negative 𝝓𝒎 𝒂𝒙 derivative of

𝜺 = −𝑵 𝟎.𝟐𝟓𝑷

IMPORTANT RELATIONSHIP 1. 2. 3. 4.

if it is a dark band then ( 𝒏 + 𝟐) 𝟏

Single slit diffraction of light 𝑑𝑦 d sin 𝜃 = 𝑛 𝜆 = 𝐿 d: slit separation L: distance from slits to screen Y: distance from centre to minimum point or n. Smaller d greater intensity fridge separation increase appear further Refraction of light When light change medium, speed will change due to wavelength change, Frequency doesn’t change. It will cause refraction. 𝑐 𝑛= 𝑣 𝑛1𝑣1 = 𝑛 2 𝑣2 n: refractive index v: speed of light in medium

Intensity of light independent Stopping voltage (K.E max) Intensity of light Photocurrent Frequency of light was used  stopping voltage (K.E max) Frequency of light was used independent photocurrent

ℎ𝑐 𝐸𝑝ℎ𝑜𝑡𝑜𝑛 = ℎ𝑓 = 𝑝𝑐 = 𝜆 ℎ 𝐸𝑝ℎ𝑜𝑡𝑜𝑛 = 𝑝= 𝜆 𝑐 𝑐 𝑐 𝜆 = ,𝑓 = 𝜆 𝑓

Particles behave as Wave 𝑝2 1 ℎ2 𝐸𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒 = = 𝑚𝑣 2 = 2𝑚 2𝑚𝜆2 2 ℎ ℎ ℎ 𝜆= = = 𝑝 𝑚𝑣 √2𝑚𝐸 Only moving particle behave as wave

Electron diffraction pattern

Single Photon/Young’s Double slit

IF photon and beam of electron pass through a crystal sample produce same wavelength produce same momentum same fringe spacing Energy of electron different from energy of photon

When the light source so weak (intensity is too low) we can conclude only one photon was passing through a slit after long tome light&dark bands patter appear evidence for Wave-particle duality

Einstein&Photonelectric effect Light travelled in discrete packets of energy and defined intensity as number of photon(N) 𝑒𝑛𝑒𝑟𝑔𝑦 𝑜𝑓 𝑙𝑖𝑔ℎ𝑡 𝑏𝑒𝑎𝑚 𝑁= 𝑒𝑛𝑒𝑟𝑔𝑦 𝑜𝑓 𝑝ℎ𝑜𝑡𝑜𝑛 (ℎ𝑓)

Superposition of waves

Energy level Eemission=E intial-Efinal Eg from energy level n=3 to ground state It will be 2 possible ways: n=3 to n=2 and n=2 to n=1. Eabsorption=Efinal-Eintial

When an object creates an external force and vibrates another object at a frequency that exactly matches one of the natural frequencies. This object then absorbs energy and have twice of amplitude

Coherent: Waves are in step or in phase (LAZER)

Polarisation Occur to transverse wave. Allowed wave to vibrate in one direction. Light show electric field perpendicular to magnetic field Vertical filter: block magnetic field horizontal filter:block electric field

n1: refractive index of medium coming from n2: refractive index of medium going to

Dispersion White light is combination of different colours of light. Different colour of light has different wavelength and travel refract differently. Lower frequency: less refract Higher frequency: more refract

Ratio 𝑛2

𝑛1 > 𝑛2

𝐾. 𝐸𝑚𝑎𝑥 = ℎ𝑓 − ℎ𝑓𝑜 K.E max is stopping voltage 1 𝐾. 𝐸 𝑚𝑎𝑥 𝜆

K.E MAX

1.Energy of the wave is dependent on amplitude, if sufficiently intense light is used, the electrons would absorb enough energy to escape no threshold frequency 2.Time delay should observe, particular at low intensities, as energy is gradually transferred to the metal by the light waves 3. Intensity of light should be proportional to K.E max

Light as Particle (Photon)

In vacuum, all magnetic wave travel at “c”

Resonance

∅

FLAW OF WAVE MODEL

Electromagnetic Wave

Incoherent: doesn’t contain same frequency and doesn’t not have wavelengths that are in phase with one another (LED)

1eV=1V eV –> J : x1.6x10^- 19 J eV: :1.6x10^-19

𝑛𝜆𝐿 𝑑 ∆𝑥: distance between any two bright band or dark band. These are equal L: distance from slits to screen d: slit separation n: number of bright band ∆𝑥 =

Light is transverse wave or electromagnetic wave. In this model, magnetic field travel parallel to wave direction and electric field travel perpendicular to wave direction. Electric field travel perpendicular to magnetic field.

DC generator

Power doesn’t affect by transformer

2.

Existence of threshold frequency: for each metal used at cathode there is unique frequency call threshold frequency if frequency of light is used < threshold frequency no photoelectrons is emitted or released from cathode Emission is instantaneous: No delay between light shining on the cathode&photoelectrons being produced/ It doesn’t depend on intensity of light

Fringe separation

Light as Wave

Coherent&Incoherent For Dc generator because of commutator reverse direction of current every half turn. So no negative area

𝒑. 𝒅 = 𝒏𝝀 Destructive (Dark band/nodal/minima/2 waves outphase ) 𝟏 𝒑. 𝒅 = (𝒏 + )𝝀 𝟐

Snell’s Law

Reflection of waves

1.

∅ = ℎ𝑓𝑜 1 𝑠𝑡𝑜𝑝𝑝𝑖𝑛𝑔 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 This is the amount of energy required to eject a photoelectron If energy of photon less than this value no photoelectron is emitted ℎ𝑓 < ℎ𝑓𝑜 Work function

IMPORTANT OBSERVATION

Constructive (bright band/antinodal /maxima/ 2waves inphase

significant diffraction

𝑉𝑝 will  by X factor

Photoelectric effect

Interference

Standing Waves

Electrons exist in discrete energy levels, for emission, when electron moves to lower level it release a photon with energy exactly equal to the difference between energy levels of atom. For absorption, when a photon/light go to an atom, an electron will absorb an energy from photon, this energy equal to energy levels between ground state and higher state. Emission spectra da rk and some colour/Absorption spectra: colour and some da rk

Practical Independent: controlled by experimenter (x-axis) Dependent: outcome of independent(y-axis) Hypothesis: suggested explanation and be tested Error: different between measured and actual value Uncertainty: maximum different from average value of repeated measurement Systematic error: affect the accuracy (incorrect use of equipment, bias) can be reduce by using calibrating equipment (more decimal place or significant figure)

Adsorption&Emission ∆𝐄 = 𝐡𝐟 =

𝐡𝐜 𝛌

Uncertainty principle&Single slit diffraction -Uncertainty in position is inversely proportional to uncertainty in momentum -Increasing the slit width, increase the positional uncertainty, decreases the uncertainty of the momentum of the particles decrease in the extent of diffraction on the screen (Less diffraction).

Standing waves of electron According to de Broglie’s model of atom. Electrons are modelled as standing waves around the nucleus. Their wavelengths are restricted to discrete values fit as only certain wavelengths will support standing waves. (Wavelength must be whole number to keep it orbiting in stable 2πr=n 𝛌 Discrete wavelengths mean discrete momenta and thus discrete energy levels which we see as quantised energy states. The reason for whole number of wavelengths is to avoid destructive interference with itself

𝜺

𝑵

cos(x) is sin(x)

Random error: affect the reliability (measure time) can be reduce by repeated experiment....