This is going to take years of writing and updating + i have to study for it So please be patient :P
Ill update when i can
Please critisize the information and help increase it
Electricity and Magnetism
Ferromagnetic or ferrous materials are attracted by magnets ( Iron , nickel , steel, cobolt )
Magnets have north pole and south pole
How do you kno what is north pole and what is south pole in a magnet that doesnt have sign?
Suspend it by a spring so that it can rotate horizontally and it will gradually come to rest with its north pole facing north and south pole facing south ..LIKE A COMPASS. Like poles repel .Unlike attract (Opposite to wires with current ..later )
A true test for a magnet is only by puttign it beside another magnet to check if both poles attract and repel.
Also if you snap a magnet in two pieces they will still be a magnet and will have north poles and south poles in teh same areas as before.
3 ways of making magnets
- By induction ( complicated process will be studied later ). Pieces of iron( temporary) or steel ( permanent ) become induced magnets when you place them near magnet.
- The magnetic material is places inside a SOLENOID connected to a D.C supply
- By stroking. The side which u stroke first becomes the same as the magnet http://www.le.ac.uk/se/centres/sci/selfstudy/mam9.htm
3 ways of destroyign magnets
- Heating by bunsen burner until it is red hot .When it cools its no longer a magnet :P
- Hammering
- By placing in an Alternating current and wiht the current still passing remove the magnet
IRON AND STEEL
Iron is a soft magnetic material ( easy to charge and easy to lose charge )--> temporary magnets
Steel is hard magnetic mat. ( hard to chagge and heard to lose ) --->permanent
Thats why we use iron in ELECTROMAGNETS. - IN JUNK YARD PICK UP /ELECTRIC BELLS / ELECTRIC RELAYS .
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Steel is obviously used in a compass ( permanent )
And in door catches
YOU HAVE TO KNOW HOW TO DRAW A MAGNETIC FIELD : http://www.magnetic-shield.com/images/faq/flux-images.jpg
A region aroun a magnet where a magnetic material will feel a force
Finding the polarity of a magnet : http://3.bp.blogspot.com/_PyvjcvYfRLk/SFoBm3bLgkI/AAAAAAAAAFw/vLfh8SXuwBw/s400/Right-Hand-Grip-Rules2.png..Twirl your fingers with the current and the thumb shows which is norht
RIGHT HAND GRIP RULE ^
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CONDUCTOR AND INSULATORS
Materials with free moving electrons ^ ^ No free moving electrons
Electrostatic
Matter is made up of electrons and when electrons are taken away from a surface they produce a static charge thats why we use insulators for this topic. Mettals cannot be used since they r good conductors and do not stay charged ( remember static = stationary )
YOU HAVE TO KNOW HOW TO DRAW A ELECTRIC FIELD : http://www.mea.or.th/internet/understanding_emf_web/emf_eng/imagebook_eng/05_charge%20and%20electric%20field%20line_s.png
A region around an electric field where a electric charge experiences a force
Remember in electrostatics Neutral objects attract charged objects ! weird but yeah :/
Some material become charged when they are rubbed. FRICTION causes some of the electrons to be pulled off. Therefore one becmes posotive ( the one which loses electrons ) and the one which gains becomes negative.
NOW IMPORTANT. : CHARGE BY INDUCTION :http://www.physics.sjsu.edu/becker/physics51/images/22_04_Charging_by_induction.jpg
Bring a charged ( lets say -ve in this case ) object beside a neutral..the posotive will attract to the negative, that leave the the posotive behind . So then we put a wire ( AN EARTH ) whihch will allow negitive to leave the from the ball to the earth . REMEMBER not to remove the negative object before the wire. we remove the wire first so no electrons could come back adn thn we remove the negative object
In the case of ( lets a +ve in this case ) object..we do the same process...except the electrons ceom up from earth adn neutralise the posotive which are left because the electrons are attracted to the +ve charged object
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ELECTRICITY
COULOMB knows as Q Unit= (C)
It is a bundle of 6 x 10^18 electrons CHARGE = (Q) look in current formula
CURRENT known as I Unit = (A)
It is a flow of electrons. Also shows how much charge flows past a point in 1 second hence --> I= Q/t
ELECTROMOTIVE FORCE ( e.m.f)
Batter emf 1V
This means that the battery gives each coloumb of charge one joule of energy
POTENTIAL DIFFERENCE
P.D across a lamp is 1V
This measn that each coouloumb of charge gives the lamp one joule of energy
Lenz LAW
This states that an induced current ( later ) always flows to try to stop the movement , which started it.
CONVENTIONAL CURRENT
This shows the direction of current from the +ve to the -ve side of a battery
ELECTRON FLOW
This shows the direction of flow from negative to posotive ...oppsite of con. curr.
Ammeter
Used to measure current . connected in series and have very very very very low resistance to allow current to pass thro and does not affect as a resistor
Voltmeter
Used to measure Voltage of anything , connected in parallel and has very very very high resistance to stop current from going thro
Switches
Open switch = off . Closed switch = on
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SERIES CIRCUIT
CURRENT IS SAME EVRYWHERE IN A SERIES CIRCUIT.
MORE CELLS = MORE CURRENT.
MORE LAMPS LESS CURRENT why?
Because you are increasing the resistance of wire , and know V=I X R ..so one increases the other must decrease !
As you add more lamps the resistance increases , if we want to find the E.M.F in a circiuim we have to add ALL THE RESISANCE , WHICH ALL THE LAMPS' resistance x I .But if u want to find the voltage of 1 lamp we just multiply the resitstance of THE LAMP only x I.
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PARALLEL CIRCUIT OPPOSITE TO SERIES
CURRENT IS DIFFERENT EVERYWHERE BECAUSE IT GETS DIVIDED
MORE CELLS = MORE CURRENT
MORE LAMPS = MORE CURENT .why? in parallel as you add lamps the total resistance decreases and kno V=I X R ..so one decreases the other must increase !
RESITANCE IN PARALEL .
CALCULATION = 1/total res = 1/r + 1/r [/color][/b]
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ELECRTICITY IS COMPLETE IN A POST BELOW
ATOMIC PHYSICS[/size][/size][/size][/size][/u][/i][/color]
You should know verythign is made of extreemtly small atoms and at the centre there is a nucleas Which contain nucleons ( protons + neutrons ) .Around the nuclease there are electrons but we totally ignore that they exist in physics ( atomic anway )
You should know the charge and atomic mass unit
charge masss
Electrons -1 1/1840 ..which is basically zero and you can say that in exmas
protons + 1 1
nuetron - 0 1
We have elements and we have proton numbers ( DOWN ) 6 and mass number (UP) 14
Proton number tells you the amount of protons adn electron 14
Mass number ttells what is in the nucleus ( protons + neutrons ). So for exacmple , If element is C
6
the proton number down ( 6 ) which means also has 6 protons and eleectron . The mass number up, tellls us proton + nucleans and we know proton therefore neutron = 14-6=8
ISOTOPS
ATOMS OF SAME ELEMENT WITH DIFFEENT NUCLEON NUMBER BUT SAME PROTON NUMBER
127 131
EX IODINE IODINE
53 53
EVIDENCE FOR THE NUCLEAR MODEL
THE GOLD EXPERIMENT ( ALPHA PARTICLES ARE + )
ALPHA PARTICLES WRER FIRE THROUGH VERY THIN GOLD FOIL AND A DETECTOR WAS MOVED AROUND THE FOIL TO CHECK THE MOVEMENTS ( I.E DEFLECTION - TWISTS - ETC)
http://www.iop.org/activity/education/Teaching_Resources/Teaching%20Advanced%20Physics/Atomic%20and%20Nuclei/Images%20500/img_mid_5329.gif
this is whats happening ^ ..you see the yellow point in the middle of of the clouds,, see how small the nucleus is compared to it?
ANYWAY YOU HAVE TO EXPLAIN WHAT IS GOING ON !
THE ALPHA PARTICLES GOING STRAIGHT WIHTOUT DEFLECTION TELLS THAT THE ATOM IS NEARLY ALL EMPTY!! SPACE APART FROM THE NUCLEUS! AND SO..
THE ALPHA PATICLES THAT WERE DEFLECTED BY SMALL ANGLES SHOW US THAT THE NUCLEAS WHICH REPELLED ALPHA PARTICLS WHICH PASSED VERY VERY VERY VERY VERY CLOSE TO IT GOT REPELLED ..TELLS US THAT NUCLEUS IS POSOTIVE. AND SO
THE ALPHA PARTICLES (ABOUT 1 IN 8000 ) WERE SURPRISINGLY BOUNCED BACK !!!!!!!!!!!!!!!!> THIS TELLS US THAT THE ALPHA PATICLES COLLIDED WITH THE TINY WEENY TINY WEENY POSITIVE NUCLEASE , SO IT TELLS US THAT IT HAS A LAAAAARGE MASSSSSSSSSSSSSSSSSS altho it is very very very teeeny weeny space between the atom but it has a high masss
RADIOACTIVITY ( UNSTABLE ELEMENTS )
UNSTABLLE NUCLEASE BREAKS UP AND RELEASES ENRGY IN FORM OF RADIOACTIVITY
WE ARE ALL EXPOSED TO BACKGROUND RADIOACTIVITY by radioactive materials in rocks , the air etc but this is very small so it doesnt affect us and does not produce any noticeable affects on our health!
BACKGROUND RADTIATION IS = 20 COUNT PER MINUTE but sicne radioacttivity is A RANDOM process it varies slightily
now we have 3 types of radiation
ALPHA PARTICLES
an alpha particle is made up of 2 protons and 2 neutrons .
It has posotive charrge (2 + ) .
Can be stopped by few mm paper or a few cm of air thats why you can avoid alpha radiation by stayin 6cm away from it !
Mass 4 units ( VERY HEAVY thats why its hard to deflect towards the negative plates )
Speed : slooooooooow caz its heavvvyyyyyyy 10% SPEED OF LIGHT
Ability to ionise : STRONG !! +4 ..OMG!!! Shocked Shocked Shocked
DEFELCTION BY ELECTRIC FIELD : DEFLECT A LITTLE TOWARDS THE NEGATIVE PLATES
DEFLECTIIN BY MAGNETIC FIELD : DEFLECT SAME DIRECTION OF WIRE ( LEFT HAND FLEM.) BUT DIFFRENT DIRECTION OF BETA
DETECTORs : PHOTOHRAPHIC FILM. CLOUD CHAMBER . THINE WINDOW G-M TUBE . SPARK COUNTER
BETA PARTICLE
Define : Fast moving electron ( light ) emitte from the nuclease when a neturon splits up into a proton and an elctron !.
It has -ve charve ( -1)
Can be stopped by a few mm of Aluminium
MASS 1/1840 = 0
SPEED : 50% SPEED OF LIGHT FAST OMG OMG
Abiltiy to ionise : Weak -1 nooblet
Deflection by electric field : tWARD +VE PLATE
deflection by mag """"""""" : OPPOSITE DIRECTION OF WIRE
DETECTORS : PHOTGRPAHIC GILM. CLOUD CHAMBER . G-M TUBE
GAMMA RAYS
IS A WAVE WIHT VERY VERY SHORT WAVELENGTH ( SHRTEST ) .I
LOOOOOOOOOL NO CHRGE AHAHHAHAHAH
MASS : ZEROOOOOOOO NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOBY
SPEED : SPEED OF LIGHT Shocked Shocked Shocked Shocked Shocked Shocked Shocked WOOOOAAAH!
REMEMBER : REDUCED BUT NOT STOPPED BY LEAD!!!!!!!!!!!
Abillity to ionis : pffffffffttttt very weak as no charge..almost neglectable !
DEFLECTION BY ELEC : NO
DEFLECT BY MAGE : NO
DETECECTORS : PHOT FILM . CLOUD CHAMBER . G-M TUBE
IONISING AFFECTS OF RADIATION
AN ION IS AN ATOM WHICH GAINED OR LOST ELECTRONS
RADIATION CAN IONISE AIR BY KNOCKIN ELECTRONS FROM ATOM
FROM ABOVE WE KNO THE BEST ALPHA THEN BETA THEN GAMMA
SPARK COUNTER
http://www.promma.ac.th/chemistry/element_property/images/spark.gif
RADIUM IOONISES AIR . POSOTIVE IONS MOVE TO CATHODE AND NEGATIVE MOVE TO ANODE. ALPHA PARTICLES CAN BE DETECED USING SPARK COUNTER SINCE ALPHA PARTICELS ARE EXCELLENT AT IONISING
G-M TUBE
http://williamson-labs.com/images/gmtube-273.gif
A tube that contains a high voltage inside a metal case that is earthed
WHY HIGH VOLTAGE ? TO ATTRACT THE CHARGED FROM TO ANODE ADN CATHODE
remember the g-m tube can detect radiations but CANNOT differentiate between the three types.
When radiation enters the tube it ionise the gas inside the tube adn there is flow of charge w hich prouduces a spark from the wire to the case. Th e posotive ions move to the cathode adn the negative electrons move to anode.
An ampliver connected to the tube clicks every time there is a spark
HOW TO DIFFERNTANE??
WELL YOU HAVE TO GET THE RADIOACTIVE SOURCE and put PAPER , ALUMINIUM AND LEAD BETWEEN the source adn the DETECTOR! (remember some can pass and some cant!)
remember always take BACKGROUND RADIATION FIRST! lets say its 20 !!
so example COUNTS PER MIN ABSORBER USED
4000 NON
2700 THIN PAPER
20 aluminium
this means some counnts are stopped ! that means this source produced ALPHA PARTICELS SINCE ITS STOPPED BY PAPER !
but wait !!!!!!!! counts did go to 20 ..that means there is also soem other radioacttive stuff.. NOW WE ADD ALUMINIUM and counts dropped to 20 that means there are beta particels!!!!!!!! but count dropped to 20 and so there are no otehr radioactive like gamma..but if there was gamma then there would still be counts!
CLOUD CHAMBER
IM NOT SURE IF ITS ON SYLLABUS SO I WONT EXPLAIN UNTIL SOME1 TELLS ME ITS ON :p
SAFETY PRECATUION
KEEP ALL RADIOACTIVE IN LEAD CONTAINORS . ( LEAD STOPS ALPHA BETA AND REDUCES GAMMA)
KEEP AS FAR AWAY FROM SOURCE AND USE TONGS TO HANDLE
KEEP EXPOSURE TIME AS SHORT AS POSSIBLE
BURY WASTES DEEP IN GROUND
RADIACTIVTY BADGE
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RADIOACTIVE DECAY
NUCLEI OF ATOMS OF A RADIOACTIVE SUBST ARE UNSTABLE AND SOONER OR LATER THEY WIL BREAK UP OR DECAY FORMIN A MORE STABLE ONE . THIS MEANS A NEW ELEMEMTN IS FORMED . NO ONE KNOWS WHEN A NUCLEAUS WIL BREAK UP , IT IS ENTIRELY RANDOM PROCESS
ALPHA DECAY
WHN A SUBTANCE EMITES ALPHA PARTICLES IT LOSES TWO PRTOTNS AND 2 NEUTRONS FROM ITS NUCLEUS
THE NUCLEON NUMBER IS REDUCED BY 4 AND PROTON NUMBER REDDUCED BY 2
EQUATION
A A-4 + 4
X ----> Y a
Z Z-2 2
BETA DECAY
RELEASE WHN A NETURON SPLITS UP INTO A PROTON AND AN ELECTRON
EQUATION
A A 0
X ---> Y + e
Z Z+ 1 -1
Gamma decay
No affect on nucleas of an atom as it has no mass or charge !
HALF LIFE OF A RADIOACTIVE SOURCE
TIME TKEN FOR THE ACTIVITY OF THE SOURCE TO HALVE
THE HALF LIFE IS TH ETIME TAKE FOR THE SOURCE TO LASE HALF ITS RADIOACTIVE ATOMS
DECAY IS RANDOM
Some isotopes have a short half -life and they decay very quick while others have a vey long adn take a long time. Value of half life is not affected by temp , presure etc.
EXAMPLE :
IODIE 131 HAS A HALF LIFE OF 8 DAYS WHEN IT DECAYS IT TURNS TO XENON 131
IF WE START OFF WITH 80MILLION IODINE 131 , EIGHT DAYS LATER THERE WILL BE 40 MILLION IDIOEN 131. THE NUMBER OF XENON-131 NUCLEI ARE INCREASE FROM ZERO TO 40 MILLION
Another 8 days ...HALF OF 40 IS ..HMMM .. 20 !..SO 20MILLION IDONE 131 AND XENEON WILL BE 60 M ...GET THE POINT??
DECAY CURVE
TOO HARD TO EXPLAIN SO YOU SHOULD VIISIT THIS SITE
http://www.astarmathsandphysics.com/igcse_physics_notes/igcse_physics_notes_radioactivity_and_half_life.html
CONCLUSIONS BY J.DARREN:M ::) ::) ::) ::) 8) 8) 8) 8) :D :D :D ;D
Say for instance when a beam of alpha particle is released at the gold nucleus, it gets diverged into three paths : one that shoots directly at the gold nucleus, one that goes past the gold nucleus, one that travels away from the gold nucleus.
Also if it is a beam of alpha particle, you may as well treat it as a current and use Fleming's Left-hand rule in calculating whether it is traveling away or into the paper as alpha particle is positively charged. In the case for beta particle, reverse the direction of the current.
Those radiation is called radioactive decay. We have alpha particle decay where 2 protons and 2 neutrons (Helium) is gone from a Radium-226 nucleus, the proton number got reduced to 86, a Radon nucleus is formed. In a beta decay a neutron in Iodine-131 gets converted to a proton, forming Xenon-131 (same mass number, but an increase in the proton number), an electron and anantineutrino is released. There is another type of beta-decay where a proton gets converted into a neutron, an electron and neutrino is released.
Half-life is the time it takes for a radioactive isotope to halve its size in a decay.
Alpha particle and beta particle would ionise Argon gas inside a Geiger-Muller tube, this is due to their respective positive / negative charge.
By the way in an experiment that requires to measure the number of alpha / beta particles emitted, be sure to subtract the background reading[/i]
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