Feilds And Particles Flashcards Preview

Physics > Feilds And Particles > Flashcards

Flashcards in Feilds And Particles Deck (103):

What happens to the EMF creates by a generator when the frequency of the magnetic field variation is doubled

EMF doubles


How can the number of Atoms be worked out if you are only given the Activity and Half-life?

Decay C = ln2/Half Life

A = Decay C * N


How can you work out the momentum of a Charge in an electric field?

eV = mv^2

P = mv


What is the equation for Voltage Turns and Current in a transformer?

V(p)/V(s) = N(p)/N(s) = I(s)/I(p)


What’s the equation for voltage and current in a transformer?javascript:;

V(p)I(p) = V(s)I(s)


How can you find the speed required for stable orbit

V = (GM/r)^0.5


How can you find the ratio of GPEs or Field Strengths of 2 objects in orbit?

Compare Relevant equations, changing values


How can you calculate maximum flux linkage on a square coil

FL = Length^2 * Turns * Field Strength

Length is squared as coil is square


What is a protons quark composition



What is a neutrons quark composition



What is a delta - quark composition



What is a delta + quark composition



What is a mesons + quark composition



What is a Meson - quark composition



Why do electrons lose energy during electron scattering

Energy transferred to making new particles with KE


During alpha particle scattering, what will happen to the number of deflected particles when energy of alphas is decreased

It will increase as the amount of time spent close to the nucleus is increased


How can the change in pressure do to temperature of a gas be calculated?

P1V1/T1 = P2V2/T2


When an electron passes through a magnetic fields why does its path curve?

When a charged particle enters a magnetic field, it experiences a force which acts at right angles to the direction of field lines and velocity (Flemings LHR)


When an electron passes through a magnetic fields why might it spiral?

Collisions with gas monocles reduce its momentum causing it to slow down


How can you increase a magnetic corse permeance

Shorter core
Fatter Core
Greater cross sectional area
More permeable material


Show that Vm-1 and NC-1 are both units for electric field strength

V = JC-1
J = Nm

V = NmC-1

Vm-1 = NC-1


Why is no EMF induced when a coil moves parallel to the line of flux?

No change in flux

EMF is proportional to change in flux


Why are radio active decay equations involving the activity always a minimum value

Because it assumes all beta particles released are accounted for


How can relativistic speed be calculated?

γ = 1/(1-V^2/C^2)^0.5


How can a graph showing probabilities of energy spectrum of beta particles released during decay suggest that other particles are emitted?

Graph shows a range of energies

As all energy is conserved during the process, the remaining energy must have been taken by other particles


What are the advantages and disadvantages of alloying metals?

Stiffer, harder, corrosion resistant, reduced expansion


What particles are leptons

electron, tauon, electron neutrino, anti electron neutrino, tauon neutrinon

And their anti particles (position etc.)


When a particle is at terminal velocity, how can you find its drag?

Drag = Weight

Weight = Mg


Suppose you could have a pendulum of length 100m with a very heavy mass at the end. Why would the accelerating force be very small for a displacement of a few mm

Displacement small to angle small

Force = mg sin x


How does the movement of a magnet in a could endure an emf?

Movement cause the wires to pas through a change in flux linkage

This induces an emf according to the rate of change of flux


Why does moving a conductive plate through a magnetic field cause a resistive force

Movement of plate induces and emf

Resulting in Eddie currents

Currents produce magnetic fields that oppose the motion

Loss of energy as heat I^2R


What is the name of a particle with a mass of 0 and a charge of +1

A Positron

It can be a proton as protons have a mass


When an electron beam passes between 2 plates (one grounded, one with positive potential) which direction will it bend towards

The positive plate


How can the shape of a flux line saddest what direction a magnet will move

The flux line wants to straighten/tighten, so it will move in the direction that allows it to do this


Why does reducing the air gap between the magnet and the core increase performance

It increases the flux


How do Eddie currents form and what are their effects

The changing flux in the iron core induce their own EMF which produces Eddie currents

The flux produced by the Eddie currents opposes the flux created in the primary coil due to lenses law

This causes a loss in efficiency due to heat


How does laminating a core increase flux?

Laminations limit Eddie currents, which would oppose existing emf


Why is the actual force between to charged metal spheres less then the value calculated by f=kQq/r^2

The charges migrate to the opposite ends of the sphere increasing the distance r


During beta decay why is the KE of the beta particles less then the total energy released

Genetic energy is taken by the neutrinos


How can you tell the difference between neutrinos and anti neutrinos

anti neutrons have a line across the top


If an resistive PD is put across a circuit with the photo electric effect, what is the equation for finding the frequency of light

hf = hf0 + eVs

Where e is the charge of an electron, Vs is the resistive PD, and hf is the threshold frequency


What is a space time diaragram

Similar to a speed time diagram, but time is plotted on the y axis, and distance on the x. Arrows are plotted inside of lines, called world lines


How can a space time diagram be used to measure distances and speeds in space

Pulses of radio waves are beamed towards an object sand reflected back. This is plotted on the space time diagram with the speed and time taken known. Therefore distance can be measured (assuming speed of light is the same for the way to the astroid, and the return journey)

Repeating this process lets us work out the speed the object is traveling


As objects move closer to the speed of light, what happens to there length mass and time

Length: Decreases
Mass: Increases
Time: Slows down


How can relativistic length be calculated

Length = Length0/γ


How can relativistic mass be calculated

Mass = Mass0 * γ


How can relativistic age and half life be calculated

Half-Life = γ*Half-Life0

Age = Age0/γ


What is the Boltzmann factors and what causes it?

As the temperature of a substance increases, the particles gain KE (Average KE = KT)

Particles collide with each other and transfer KE. Its is possible for some particles to gain KE

As a result these particles can take part in an activation process (e.g. gas monocles leaving the atmosphere, or electrons moving from the valency band to the conduction band) which involves the breaking of bonds.


Show that N increases as T increases due to Boltzmann factor


As T increases, kT increases, as kT increases, as kT increases e/kt decreases, as e/kt decreases, e^(-e/kt) increases, therefore N increases


How can youmw0rk out the number of collisions required for a particle move up an energy level during he Boltzmann factor

number of collisions needed is 1/fb


How can you work out the momentum of an electron in the standing wave trapped in a box model

Mv = h/wavelength


How can you work out the total energy absorbed by a body fro, radiation over a period of time

Energy = dose*mass*years


How can you find the radius of an electron travelling through A magnetic field

Bqr = Ke (of electron)


How can maximum rate of change influx be calculated

Rate of change of flux = e/n

Where E is induced emf and n is number to turns


When the magnet Falls through a coil of wire how is EMF induced and what form is it in

EMF is related to rate of change in flux

Induced EMF falls as more magnet enters coil

When magnet is fully inside EMF is zero

As the magnet leaves flux is decreasing so negative emf induced


Explain how microwave background radiation is evidence of the Big Bang

Following the big bang, the universe was filled with gamma radiation, as the universe expanded the e-m radiation experienced a gradual wavelength increased

Estimates stated that the e-m radiation should have a wavelength in Microwave Region

In 1964 cosmic back ground radiation, and this was seen as further evidence to support the big bang theory


Explain what the Hubble constant is and how the age of the universe can

Hubble plotted a graph of recession speed to distance of galaxies

The trend was directly proportional and thus created the equation:


The gradient of the graph gives H0, 1/H0 gives the age of the universe


How can spectral analysis be used to find speed of recession

Consider the spectrum of a source of hydrogen that is:
Undergoing relative motion away from the observer

If the change in wavelength can be measured, the speed of recession v can be calculated using:


The fact the light received from distance stars is redshifted, it shows stars are moving away, this observation supports the big bang


What is the equation for KE of a charge moving through an electric field

Energy = Vq = 1/2 mv^2

where v is PD and q is charge of a particle


What is the equation for Electric Field Strength


where v is PD and d is the distance between plates


What is the equation for force on a charge in an electric field

F = Eq = Vq/d

where v is PD and d is the distance between plates q is the charge of an electron, and E is the field strength


What is the equations for the force on a charge in a magnetic field

Force = Bqv = (mv^2)/r = mw^2 r


What is the equation for velocity of a charge in a magnetic field

Bvq = (mv^2)/R

v = BqR/m


What is the equation for the force of a particle in both a magnetic and electric field

Fe = Fb



Derive an Equation for the Average KE for a gases particles

pV = NkT

pV = 1/3 Nm(c^2)

1/3 Nm(c^2) = NkT

1/3 m(c^2) = kT

1/2 m(c^2) = 3/2 kT


What is pair production and how can the minimum energy be calculated

A photon of EM radiation is converted into 2 particles, a particle and its antiparticle
During this process momentum and energy must be conserved
The minimum energy required to produce the particle antiparticle pair is given by:

E=2M C^2

Where M0 is the rest mass of each particles


What is pair annihilation and how can the energy go each photon be calculated

When a particle and an anti-particle come together and produce 2 photons during mutual annihilation
Two photons must be produced to conserve the momentum and energy (this assumes particles are stationary)
The energy of each photon is given by:

E=M C^2


What is the definition of binding energy

Nuclear Binding energy is the energy required to split a nucleus into its constituent nucleons (protons and neutrons)


How can during radioactive decay the proton number go up with the mass number stays the same during beta decay

One of the Neutron converts to a proton, an electron, and an antineutron


What are lepton Numbers

All leptons have a lepton number of 1, all anti leptons have a lepton number of -1, all other particles have a lepton number of 0. The lepton number needs balanced


Why is the Energy spectrum of beta particles continuous and not discrete as expected from the energy diagram?

Energy is shared between the beta particles, and the neutrino in a random way


How can wavelength of electrons be calculated if given only their momentum

Wavelength = h/p

where h is Plancks constant, and p is momentum


Which Particles are Hadrons

Protons and Neutrons


What will happen ti flux density if cross sectional area is halved

flux density halfs, flux stays the same


Why are high temperatures needed to fission

Energy needs to over come repulsive force between nuclei


How is field strength related to distance in a radial field



How is potential related to distance in a radial field



Why can there be a field strength E but no potential, V between 2 equal and oppositely charged particles

Potential, V at mid point is equal at both, but charges are opposite (potential at MP is P1+P2) as potential is a scaler

Field Strength, E is also equal and opposite. (FS at MP is P1-P2) as F is a Vector


How can you find relativistic velocity of an electron moving through a PD

γ = Total E/Rest E

γ = 1/(1-V^2/C^2)^0.5


Whats the unit for rate of change in flux linkage



What direction is field strength at equipotentials

Outwards, away from max potential


How do alternating currents vary during a motets complete revolution

Net flux is sume of coils 1 and 2

Direction of flux changes from max to min at each coils in XX seconds

By 2xx seconds its back to original

After 4xx seconds its back to original position


How can 2 wave forms have equal pitch but different sounds

Same time period (frequency)

Most complex note in one has higher frequency components


What materials does the photo electric effect work for



What is the work function

The minimum energy required to liberate an electron from the surface of a metal


What is the threshold frequency

Tne minium frequency of a photon can have to liberate an electron from the surface of a metal


What happens if a photon with an energy above the work function collides with a metal

The extra energy is taken as KE


What is the stopping voltage or stoppage potential

The voltage required to stop an electron thats been emitted by the photo electric effect


How can you derive an equation to find the stopping voltage required for a frequency of an photon

hf = hfo + Vse

Vse = hf - hfo

Vs = hf/e - hfo/e

Where Vs is stopping voltage fo os the threshold frequency and the x intercept is the threshold frequency


How can you find the effect of changing a variable in an equation

Devide equation by each other

Cancel out constants leaving only variables

Put change in variables


How can you work out the energy absorbed by a mass from radiation

Exposure * Mass


How can you work out energy absorbed per unit mass from radiation

Energy Absorbed/Mass


How can you find % of particles remaining after a given time from a radio active decay

No. Half Lives = Time Elapsed/Half Life

% remaining = 100 * 0.5^No.Half lives


What is the wavelength of visible light



When charging a glass ball with static electricity why won't the whole ball become charged

Glass is an insulator, so charges can't move freely within it


What is ohms law



What are the names or particles made of quarks



How can they determine the quark structure of a nucleon

Deep Inelastic Scattering which is when they fire a stream of electrons towards a nucleus


Why do we need to include neutrinos during radio active decay

To account for the continuous energy spectrum of beta particles emitted during beta decay, and to balance the lepton numbers


How can you find velocity form angular velocity and



Which fundamental particles are involved with Weak and Strong interactions

Weak - Leptons
Strong - Hadrons


Why can fission occur even though strong nuclear force is much greater then the electric repulsion force

Strong nuclear force only binds with its nearest neighbours but the electro-repulsion force acts at an infinite distance


How can you find the acceleration of an orbiting body of you know the field strength acting on it from the object is orbiting

Acceleration is equal to field strength