relate current and charge for steady and changing currents

For a steady currentQ = It

For a chnaging currentQ = ItI = dQ/dt

explain the meaning of drift velocity and relate it to the current in aconductor

Is the average velocity a charged particle (like an electron)moves through a material.I = nvAq

n = number of charge carries per m^3velocity of carriersA = cross-sectional areaq = charge of each carrier

define potential difference and know how it could be measuredwithout a voltmeter

The p.d. between two points is the electrical energy converted intoother forms of energy when 1 coulomb of charge passes from onepoint to the other

define the e.m.f. and internal resistance of a cell and explain how tomeasure these quantities

The electrical energy produced per unit charge inside the source.

sketch graphs to show the characteristics of different componentsexplain how to measure the resistivity of a material

Chapter 22 | Current and Charge

carry out circuit calculations for circuits that include resistorcombinations

use Kirchholf's laws to carry out circuit calculations on circuits thatinclude more than one cell

calculate the charge and energy stored in a capacitor and incombinations of capacitors

carry out capacitor charge and discharge calculations

use an ammeter to measure current or a voltmeter to measurepotential difference

carry out calculations to extend the range of a meter

describe and explain the principle of the potential divider

use a potentiometer to compare e.m.fs and to measure small e.m.fs

explain the principle of the Wheatstone bridge and use it to measureresistance and in sensor circuits

carry out appropriate calculations on the Wheatstone bridge

explain thermionic emission and the production of an electron beam

carry out calculations on charged particles in electric and magneticfields

describe a method to measure the specific charge of the electron,e/m describe Millikans method to determine e

outline the significance of the measurement of e/m and of e

describe the principle of the mass spectrometer, the TV tube and the

Chapter 23 | Meters and Bridges

Chapter 27 | Properties of the electron

oscilloscope

use the photon theory to explain photoelectricity

carry out calculations using Einsteins photoelectric equation

describe the properties of alpha, beta and gamma radiation

describe experiments that demonstrate the properties of alpha, betaand gamma radiation

state the equations for each type of radioactive decay

explain the principle of operation of different detectors of ionizingradiation

describe Rutherford's alpha scattering experiment and how it led tothe nuclear model of the atom

describe methods used to estimate the size of the nucleus

describe the discovery of the neutron

Carry out half-life calculations and describe how to measure half-life

describe and explain ionisation and excitation by collision

Ionisation

Is the process of creating a charged atom by the additionor removal of an electron.To create a negatively charged ion you must give it enoughenergy to escape the pull of the positively charged nucleusThree ways to create ions in the air include:

Allow radioactive particles to pass through the airStriking a match

Chapter 28 | Radioactivity

Chapter 29 | Electrons inside the Atoms

Using a beam of electrons from an electron gun

The first two methods work by giving energy directly to theelectrons whilst the third works via passing kinetic energy via acollision between two electrons.By adjusting the voltage at the anode; you can change thespeed of the electronA thyratron valve can be used to demonstrate ionisation bycollision.

The valve contains an inert gas like xenon. Increasing theanode voltage gives energy to the electrons however wesee little to no change in the current (as shown below) until12.1V.At 12.1V, electrons have the right amount of kinetic energyto ionise the inert gasThe ion moves towards grid plate which gives us the extracurrent which can be measured

Excitation

Is the process whereby electrons absorb energy withoutionisationWe can modify the thyratron valve to measure the electronsreaching the anode and we get the following graph:

As we increase the voltage the number of electrons reachingthe anode increases hence the current increases until 8.4vwhere in Xenon the energy is absorbed hence causing the

current to dropAt this point the electrons are in an excited stateDifferent gasses; absorb energy at different energy levels

relate excitation energies to energy levels and possible photonenergies

When an atom absorbs energy; it's released in the form of ultra-violetradiationYou can find the energy of the emitted photon using it's wavelength:

Energy is absorbed by the atoms in fixed amounts

relate energy level diagrams to possible photon energies

As electrons move down energy levels they release photons ofspecific wavelength/frequency from which we can calculate theirenergy

The hydrogen spectrum follows a specific pattern for it's energylevels. Others don't follow this simple pattern because theelectrons interact with each other.

electrons can travel multiple routes to ground state from an excitedstate. As shown in the diagram below:

As you can see there are nine possible routes/transitions;therefore there are nine possible wavelengths of energy thatcan be emittedLine emission spectrum is a graph of intensity (photons persecond) against wavelength.

Peaks appear where there are a lot photons being

released which indicates an energy level

Line absorption spectra is essentially when white light ispassed through a material and different parts of the spectrumget absorbed by the electrons.

We see throughs where there is absorption and thatabsorption indicates an energy level

describe the main features of atomic models that explain energylevels

Bohr developed a model of an atom as a solar system to betterunderstand energy levelsthe electron is in a circular motion around the nucleus where thecentripetal force is provided by the attraction between the nucleusand the electronBohr made a bold assumption of the angular momentum of anelectron being in lumps of h/2piWhen calculating energy released from de-excitement we do:

hf = initial energy (e.g -13.6 ev at n=1) - final energy (-3.4ev atn=2)

state the assumptions of the theory of special relativity and outlineevidence for the invariance of the speed of light

Physical laws have the same form in all inertial frames (frame ofreference which obeys newtons first law)The speed of light in free space is constant(/invariant)3 key points of evidence:

Time Dilation - a moving clock runs slower then a clock that isstationaryLength Contraction - a rod moving in the same direction as it'slength appears shorter when movingRelativistic Mass - mass of an object increases with velocity

use E=mc2 and the relativistic equations for length contraction, time

Chapter 30 | Nuclear Energy

dilation and mass increase

Einstein's relativistic mass formula shows no object can reach thespeed of light because at that point the mass would be infiniteSupplying any form of energy to an object increases it's mass withaccordance to E=mc2

sketch the binding energy curve and carry out energy calculationsfor nuclear reactions

The mass of separated nucleons is always greater than the mass ofthe combined mass of the nucleusmass defect is the difference between the mass of separatednucleons and the combined mass of the nucleus1u = 1.66*10^-27 = 931 MeVbinding energy of a nucleus is defined as the work done to separatea nucleus into its constituent neutrons and protonsbinding energy curve is the plot of all known isotopes's bindingenergy against their mass number

most stable isotope is at A = 50 as the binding energy is the greatestherethe nucleons are not as bound together at the maximumwhen a large nucleus disintegrates each nucleon becomes part of asmaller hence B.E. per nucleon increases.the nucleons in the product nucleus are far more tightly bound so theenergy released during the disintegration is equal to the increase inB.E.

the loss of P.E. (and increase of B.E.) is released as K.E.in fission a large nucleus disintegrates into two equal smaller nucleiradioactive disintegration occurs where the original nucleus lossesan alpha, beta or gamma particle.

where an alpha & beta particle are released both lead to anincrease of B.E. per nucleon and hence release energy as K.E.of the products

Fusion occurs when two light nuclei join together with a massnumber of less than 50. The B.E. per nucleon is increased so energyis released when the nucleons fuse together

explain the origin of the neutrino hypothesis

Puali suggested that an additional particle called a neutrino is alsoemitted during beta decay which is responsible for missing energyif the neutrinos share of the energy is negligible then the betaparticle's K.E. is almost equal to Q because it's much lighter than therecoil nucleus.

Hence K.E. max is equal to Q.

describe the principles of nuclear fission

uranium nucleus splits into two, each of it's nucleons becomes a partof a nucleus about half it's size hence the B.E. per nucleon increasesby roughly 1 MeV. So, approximately 1 MeV of kinetic energy isreleased and since uranium as around 200 nucleons that means 200MeV being released - this is a lot.a single uranium nucleus might release two more neutrons whichcan bombard and cause fission to two more radioactive nuclei whichrelease more neutrons which do the same. This process is a nuclearchain reaction.

describe the main features of the thermal nuclear reactor

critical mass of fuelthe minimum mass capable of producing a self sustaining chainreaction

choice of moderatordo not absorb the released neutrons but help to scatter them

choice of control rodabsorb neutrons rather than scatter them

type of coolantpumped from the core of the reactor to the heat exchangerwhere where it's used to produce steam to drive the turbines

treatment of wastein the form of spent fuel and fuel cans

it's radioactive

safe storage and cooling of fuel rods as they get extremely hotwhen radioactivespent fuel is removed from cans and reprocessed to recoverany fuelunwanted material is stored is sealed containers until it is nolonger radioactive

describe the principle of the fast breeder reactor

Makes use of U-238 which makes up 99% of natural uranium andplutoniumPu is fast fission by neutrons without the need of a moderatorit's surrounded by U-238 nucleiwhen the Pu releases a neutron from disintegrating; it is absorbed byU-238 which becomes Pu creating a chain reaction.

explain energy release due to nuclear fusion

Essentially, after the two light nuclei fuse the binding energy of theproduct nucleus is greater than the of the initial hence energy isreleased

describe the main difficulties associated with a fusion reactor

Plasma Heating - Needs lots of electricity to reach the temperaturesneeded for plasma which easily conducts electricity.Plasma Confinement - Plasma will melt anything it touchestherefore it must be confined. Current methods include using anelectromagnetic field however it is difficult to restrict the plasma'smovement.

Panos of my library workspace