Physics P3 27/5/2010

[WARRIOR]

This is going to take years of writing and updating + i have to study for it So please be patient
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
• 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

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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
-------------------------------

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
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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[PeaceMaker]

This is going to be great! should help out alot. But anyways, did you take ur maths exam? how was it if so? Im going about 30 minutes, i dont feel worried nor nervous but im going to do my best and if my best was my worse then so be it. Allah yewafegni inshallah.

[WARRIOR]

  

THERMAL PHYSICS

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I am not going to explain the STATES OF MATTER (solids liquids and fases afcourse )  but you have to know

DIST between molecules , forces between molecules , motion of molecules , shape and finally diffusion

Presuusre from a gas is because the molecules ARE HITTTING THE WALLS of the container which provides a force over an area .( Pressure is same on all wals since gas move in a  continous RANDOM rapid motion

When u increase temp of gas, molecules gain
K.E-->Hit walls harder -->Hit walls more often

BROWNIAN MOTION
SHINING BRIGHT LIGHT INTO SMOKE PARTICLES WHICH REFLECT OFF IT , you will see tiny dots of light moving in an irrefular motion( random)
why?
Tiny , fast moving air molecules which are in constant random motion are hitting the larger smoke particles from all direction

                                                                  EVAPORATION
It is when molecules are surface of a liquid have enough K.E to escape from the surface
FACTORS That affect evaporation
             Wind : wind blows any fast moving molecules that have escaped from surgace leaving more room for the next moolecules to escape
           Temperature : The heat gives the water mol. enough K.E so they escape from the surface faster
         Surface Area   : Number of surface molecules increases so more molecules escape

Difference between evaporation and boiling?
Evaporation occurs at any temperature . Boiling occurs only at boiling point
Evaporation occurs at surfact of liquid , no bubbles. Boiling occurs within the liquid , bubbles appear

         WHY do we feel cool after a shower?
Molecules with most kinetic energy at the surgac of skin escape and so the ave. K.E of the remaining moecules decreases adn temperature falls.

    Gases experiment - Constant Volume
The volume and mass of gas  is kept constant  and the cylinder with gas in it is heated.
     Molecules have more K.E ..hit container more harder and  more ofter
                            -Constant temperature
Temparute asn mass of gas is kept contant and the piston in the cylinder is pushed to volume decreases .
     Pressure is inversely proportional to volume
    The gas have less area to hit and therefore they hit container more ofter and therefore pressure increases
                            - Consant Presuure
Pressure and mass of gas are kept constant  and the cylinder is heated
Gas molecules ggain kinetic energy adn push the piston outside adn the volume increases. ( since volume increases pressure stays teh same no matter how much u heat )


Formula for gas laws

 P.V.= P,V,
Pressure 1 x volume 1 = pressure 2 x vollume 2


TEMPERATURE
MERCUTRY /ALCOHOL THERMOMETER + THERMOCOUPLE

In order for anythin to measure temp. we  have to CALIBRATE IT

how do we do that with mercury thermometers?
Measure upper fixed point ( 100* C) by puuting the thermometer over steam above pure boiling water at normal atmospheric pressure , 100* C

Lower fixed point ( 0*C) PUT IT IN PURE MELTING ICE  

and theen divide those 2 points into 100 equal divisions

RANGE: from minimum temp to max temp on teh scale . for ex on mercury thermometer its from 0-100
How to increase teh range?? ( common sence )

Increase the length of teh capillary tube. Or use a liquid which expands less when heated

SENSITIVITY -how much liqiuid expands for every degree rise in temperature !
A thermometer with high sensitivity expands alot for small degree rse in temp.
You can increase senitivty if
Use a liquid tht expands more whn heated therefore rise up the capillary tube further
Bulb of the therm. is mad ethinner
Make a narrow ca[illary tube , so tht expansion move liquid a long way
Capillary hould have a vacuum so liquid can .....^

LINEARITY :-liquid should expand same amouunt for every degree rise


                                   Thermocouple
 OPEN OCTOBER NOVEMBER 2004 QUESTION 4 AND SEE HOW IT LOOKS LIKE
Is made out of 2 differnet metals and a CALIBRATED ( IN DEGREE CELCIUS ) GALVANOMETER
There is a hot junction and a cold junction. The cold junction is put in pure melting ice ( 0*C) and the hot junction is put in the hot objct. The difference in temperature causes a current in the wires. This leads to a reading in teh galvanometer ( calibrated )

by darren ( cheers mate ): Consists of a copper wire, Constantan wire, a hot junction, a cold junction and a digital meter. Due to temperature difference there would be a current flow between the two wires. The greater the temperature differnce, the greater the current. The digital meter converts the current reading into temperature.

ADVANTAGES
HAS A LOW S.H.C can heat up very fast and measure fast changin temp
Measures very high temperatures
They dont take much heat away frm the object they are measuring .

Thermal Heat Capacity
Heat needed to raise the temp of 1Kg of a substance by 1*C
Energy ( Pxt ) = S.H.C X Mass X Change in temp.

S.H.C unit = J/Kg*C

Sometimes while finding the S.H.C the value is usually different because of reasons like :
Heat gained from surroundings , therefore the reading is a bit less because CHANGE IN TEMP IS TOO LOW ( if u substitute the formula u will find out why )

LATENT HEAT
SPECIFIC LATENT HEAT is teh energy needed to change state of  1KG of substance

E ( P xt ) = S.L.H x M

Unit is : J/Kg
 What is latent heat?
Well when your boiling something there is no increase in temp. Why? This is because of latent energy . This energy is used NOT TO HEAT THE WATER but to break the bonds ( or form ) and sperate and therefore change state! AND NO TEMP. RISE

During boiling a substance takes latent heat from surrounding ( heat is taken in to break bonds ) same wiht melitng
During condenstion a subtance looser latent heat to surroundings ( heat is given out to form bonds ) same wiht solidyfing

The is latent heat of fusion . When solid turns into liquid
The is latent heat of vapourisatoin . When liquid turns into a gas.

WHCH ONE IS HIGHER???
THE LATENT HEAT OF VAPOR.. why ? becaus more energy is needed to sperate molecules so faaaaaaaaaaar apaaaaaaaaaaaaaaaaarrrrrrrrrrtttttttttttt   and break the forces of attraction!

now again there are wrong experiment with finding the latent heat..some gain extra energy and therefore there are sources of error. and you have to kno where tey come from ..etc like the S.H.C i mentioned previously

CONDUCTION - CONVECTION ADN RADIATION
solids              Gases + liquids -    Anythign hot that releases heat

Metals once heated particle starts vibrating and caz theyr so cloose they pass kinteic enrgy to each other and start vibratin ( particle to paticle transfer  
Also metals are good coducter caz they have free electron to carry energy and GUESS WHAT INSULATORS DONT HAVE FREE ELECTRONS SO THEY ARE BAD CONDUCTORS
USE OF BAD CONDUCTORS : AIR--> IN DOUBLE GLAZING. > TO WINDOWS SPERATED BY AN AIR SPACE . KEEP WARM DUTING WINDER AND COLLER IN SUMMBER CAZ DONT ALLOW HEAT TO ESCAPE AND DOTN ALOOW HEAT TO COME IN
WOOD IN SAUCEPANS KETTELS ETC
FIBREGLASS : COTTON LIKE MATERIAL WHICH STORES ALOT OF AIR AND THERE IS INSULATOR , FOR EXMPLE ROOF INSULATION . SO DOESNT ALLOW HEAT TO ESCAPE

CONVECTION
http://www.uoguelph.ca/geology/geol2250/glossary/HTML%20files/convection.jpg
^ this explains everything . you should know that hot air / water is less dence than cold air and so rise and cool air replaces it adn thn when the hot air/water rise it cools down as becomes more dence and therfore you see that cycle !

you should kno example of convection : heaters in house..refreigerators..etc

RADIATION :
CAN TRAVEL TRHO VACUUM.ELECTROMAGNETICE WAVE. SPEED OF LIGHT .
BEST EMMITOR AND ABSORER : DULL BLACK SURFACES .WORS EMMITOR ADN ABSORBER : SILVER WHITE SURGFACES

[WARRIOR]

ELECTRICTY PART 2---ALL OF THIS IS BY J.DARREN ( CREDIT TO HIM ) THANKS !!   A MUST + REP GUYZZ!!

A reed switch is operated by a magnetic contact, when a piece of metal is brought near, the two contracts are ... well, in contact. When this arrangement is connected to a coil, it is connected to a circuit, hence when the two contacts are in contact, it completes the circuit and switches on, say a buzzer.

Another form of relay would be the magnetic relay.

http://www.irrigationtutorials.com/control1.gif

As shown above, when the switch is closed, the contact of the relay and the current with a pump is brought in contact, thus completing the output circuit (the one with a pump), it is then switched on. There is another form of relay where the contact is normally closed, and detaches when the switch is closed.

Circuit breaker

http://static.howstuffworks.com/gif/circuit-breaker-diagram.gif

The current flows through both terminals, this is an example of a normally closed relay as the contacts are normally closed. When the current gets strong enough, the pull from the electromagnet would release the iron catch, which detaches the contact and prevents current from going through. The switch is essentially a reset button which, by pressing it, enables you to close the contact again.

Magnetic field around a wire - Right hand grip rule (The fingers are pointed in the same direction as the magnetic field whereas your thumb is pointing in the direction of the current)

- The field lines are circles
- The field closest to the wire is the strongest
- Increasing the current would increase the overall field strength

A question from the 08 (?) Paper 3 asks what happens if there are two such magnetic field which interacts with each other. In this case they get attracted to each other.

Magnetic fields from coils - Right hand grip rule (Working out the poles - The direction which the thumb is pointing is the North pole, whereas the direction of your fingers represents the direction of the current)

- There are magnetic poles at both ends of the coil
- Increasing the number of turns in the solenoid increases the strength of the magnetic field
- Increasing the current increases the strength of the magnetic field

Magnetic force on a current - Fleming's left hand rule

Fleming's left hand rule

Thumb : Force

Index finger : Magnetic field

Field direction : North to south

The finger : Current

Current direction : Positive to negative

The wire moves across the magnetic field without being attracted to either poles.

- The produced force increases if a stronger magnet is used
- The produced force increases if the current is made stronger
- The produced force increases if the length of wire is increased



Turning effect on a coil - Fleming's left hand rule

The coil is placed between the poles of a magnetic field. The current flows in opposite directions along the two sides of the coil. According to Fleming's left hand rule. One side is pushed up and the other side is pushed down. With more turns in the coil, the turning effect is increased.

DC Motor

- The coil is made of insulated copper wire.

- The motor runs on Direct Current (Obviously !)

- A device called commutator changes the direction of the current when the coil is nearly vertical. The carbon brush enables the coils to overshoot each other. The forces changes direction and keep the coil turning.

- The coil keeps rotating clockwise, half a turn at a time. This is because that the direction of the forces are reversed when the coil is nearly vertical as it overshoots the commutator. Reversing the battery or the poles of the magnet would cause the coil to rotate anticlockwise.

- The turning effect on the coil increases if a stronger magnet is used
- The turning effect on the coil increases if the area of the coil is increased
- The turning effect on the coil increases if the number of turns of the coil is increased
- The turning effect on the coil increases if the current is increased

Electromagnetic Induction - Moving wire

When a wire is moved across a magnetic field, an electromotive force is induced in the wires. As the wire forms part of a complete circuit, the emf makes a current flow.

Faraday's law of electromagnetic induction

The emf induced in a conductor is proportional to the rate at which the magnetic field lines are cut by the conductor. By taking the measures below, the emf induced in a conductor (wire) would increase proportionally as the the magnetic field lines are being cut more frequently.

- The induced emf and current incrases by moving the wire faster.
- The induced emf and current incrases by using a stronger magnet.

Bear in mind that the magnetic field lines are used to represent the strength of a magnetic field as well as its direction. The closer together the lines, the stronger the magnetic field.

- The induced emf and current incrases by increasing the length of the wire in the magnetic field.
- The induced emf and current incrases by looping the wire.

Moving the wire in opposite direction or reversing the poles of the magnet will reverse the direction of the induced emf and current.

The current flow can be detected by a device called a galvanometer, its pointer moves to the left or right, depending on the direction of the current.

Electromagnetic Induction - Coil

- If a bar magnet is pushed into a coil, an electromotive force is induced in the coil.
- The field lines of the magnetic field caused by the bar magnet are being cut by the coils.
- As the coil forms part of a complete circuit, the emf makes a current flow.

- The induced emf and current incrases by increasing the number of turns in the coil.
- The induced emf and current incrases by stronger magnet.
- The induced emf and current incrases by moving the magnet faster.

- If the magnet is pulled out of the coil, the direction of the induced emf and current is reversed.
- If the S pole of the magnet, instead of the N pole, is pushed into the coil, it reverses the direction of the current.
- If the magnet is held still, no field line is cut, no emf and current are induced.

The current flow can be detected by a device called a galvanometer, its pointer moves to the left or right, depending on the direction of the current.



Lenz's law

- If a bar magnet is pushed into a coil, a current is induced in the coil.
- If a bar magnet is pulled out of a coil, a current is induced in the coil.

According to Lenz's law, an induced current flows in a direction such that it opposes the charge which produced it.

The Lenz's law is an example of the law of conservation of enerrgy as energy is spent when a current flows around the circuit, energy must be spent to induce the current in the first place. The energy spent in this case would be the energy required to overcome the opposing force of the magnetic pole of the coil against the bar magnet which has been pushed in.

My way of remembering Lenz's law : When you push a bar magnet into the coil, the current runs away from the magnet. However when the bar magnet is being pulled out of the coil, the current does not want the magnet to go and chases after it.

The direction of the magnetic poles can be predicted using the right hand grip rule. The direction which the thumb is pointing is the North pole, whereas the direction of your fingers represents the direction of the current.

AC Generator

- Alternating current (AC) is generated (Obviously !).

Transformer

- AC voltages can be increased or decreased using a transformer.
- The transformer works by mutual induction.
- Alternating current flows throught the primary output.
- An alternating magnetic field is created in the core.
- The changing field induces an alternating voltage in the secondary coil.

In the case of an 100% transformer, the following equations applies :

output voltage / input voltage = turns in output coil / turns in input coil

input voltage x input current = output voltage x output current

- A step-up transformer has more turns in the secondary coil.

Examples include : Power stations - A step-up transformer increases the voltage to the level needed for overhead power cables.

- A step-down transformer has fewer turns in the secondary coil.

Examples include : Battery charges and computers - A step-down transformer reduces the voltage of the AC mains to the level needed for other cicuits.

If a transformer is connected to DC supply, it may damange it as the high current which flows through the input coil can result in overheat
- The coil is made of insulated copper wire.

- The coil is rotated by turning the shaft.

- A device called slip-rings is fixed to the coil and rotates with it. The carbon brushes keeps the coil connected to the current by rubbing against the slip rings.

- When the coil is rotated, it cuts magnetic field lines and generates emf. This makes the current flow.

- As the coil rotates, each side travels upwards and downwards. Similarly, the current flows forwards and backwards. In order words, the current is AC.

- The turning effect on the coil increases if a stronger magnet is used
- The turning effect on the coil increases if the area of the coil is increased
- The turning effect on the coil increases if the number of turns of the coil is increased
- The turning effect on the coil increases if the coil is rotated faster.

Mutual Induction

Imagine that we have an electromagnet (iron core) which is being wrapped by coil and is connected to a power pack, which also has a switch. Right next to it we have a coil, connected to a galvanometer. As the switched is closed, an emf is induced in the other coil, but only for a split second. It is the same as pushing a magnet towards the coil very fast. As a steady current now goes through the electromagnet, since the magnetic field is not changing, no emf is induced. When the electromagnet is being switched off, an emf is induced in the other coil in the opposite direction, but only for a split second. It is the same as pulling a magnet away from the coil very fast.

- The induced emf at switch on and switch off is increased if the number of turns in the other coil is increased.
- The induced emf at switch on and switch off is increased if the core of the electromagnet goes right theough the other coil (Parallel to each other).

[falafail]

i dont think anyone is gonna bother reading this..its too much..

i would if i were doing p3.

[The Golden Girl =D]

ya kimo ....7ato23d tiktab ma8al 6olu add 7ayatak kila .... lol

well i am tryin to be sarcastic (so not me    ) but i am proud of u and happy that u really want  to help , if u need anythin in writting this ma8ala don't hesistate to ask for my help

(By the way i was kiddinn abt the first part)

cya

[WARRIOR]

            

GENERAL PHYSICS

[/color]\
not much i can do bout this but anway  ill tell you what you need to okno

DENSITY - MASS/VOL Kg/m3 or g/cm3

Mass of regular solid : PLace onto a balance / Volume ( cube or cuboid ) Lxbxh   /
NOTE : if u are given spring balance then the weight should be found first and then Divide by 10 !! to find mass

You have to know how to find the volume of irregerual solids ( the volume experimetn or displacement experiments )

You have to know difference between SCALAR QUANTITIES ADN VECTOR QUANTITIES
SCALAR HAS ONLY SIZE ex. temperature , mass , time
VECTOR HAS SIZE ( MAGNITUDE ) AND DIRECTION  ex. velocity  weight , acceleration , force

acclration = chage in velocity / time   .. unit : m/s^2

Distance time graphs : very rare  but you have to know what the gradients mean !!!

http://www.gcse.com/fm/dtg.htm this is the perfect site for this . JUST CLICK ON NEXT PAGE ( AWSOME   )

Speed time graphs

http://www.gcse.com/fm/stg.htm

TO CALCULATE THE DISTANCE : AREA UNDER GRAPH !! ( COULD BE TRIANGEL /TRAPEZIUM  RECTANGLE )

Acceleration due to gravity ..
On the moon a hammer adn geather will fall at the same time Why? Caz there is no air resistance ! and  theyll have the same constant acceleration  but on earth there s air resistance !!  which reduces the downward aceeleration of the featehr faster than it can do with the Hammer . And so hammer reachers first.  Why is it easier to lift on the moon??
1. NO AIR RESISTANCE
2. WEIGHT IS LESS ON MOON W= MX G and g is  < 10

remember force = M x a is the RESULTANT FORCE ! you have to know how to draw them E PAPER 3 JUNE 2006

You have to know the parachute jump



force down = weight or force of graivty  force up = air resistance or drag ..you should know terminal velocity


http://www.yenka.com/freecontent/item.action?quick=55 <--- this is the graph on the left

One he steps out of plane the only force acting on him is weight and so there is a resultant force downwards !! and he accelerates downwards with an accelration of 10 m/s^2 . AS he gets faster he can feel air resitance pushin on him harder and harder and the upwards force due to drag increasers .SO this decreases the resultant force and so acceleration decreases !! UNITL

THE WEIGH FORCE = AIR RESISTANCE FORCE . And so no resultant force and so no accelraton ! and falls at a steady speed ( terminal velocity )

Then the parachute opens
Parachute has a large surface area and so more air resistance can act no w!!! and this creates a sudden rise in air resistance force  and the jumper slows down . As he slows down the new air resistance force decreases and he falls down a steady speeed until he reaches the ground

CENTRIPETAL FORCE . ( force acting on any object moving in a circle )

Acceleration and constant speed :O :O

When an object is moving in circele and a const. peed its direction is changing constantly !!! This means velocity is also changing and so it is accelrating thought its speed is constand

REMEMBER ACCELRATION IS A VECTOR QUANNITTIY AND AND SPEED IS SCALAER

VECTOR = MAGNITUD + DIRECTION                                       MAGNITUDE  ONLY

Centripetal force in spring is cUSE BY TENSION . IN ROAD IS CAUSED BY FRICTION BETWN ROAD AND TIRES . IN SATELTIE IS CASUED BY GRAVITY .

When there is not enough friction / tension / gravity there will not be enough centripetal fore to keep car movin in a circle and will fly of in a TANGENT .

EQUILIBRIUM !
moment = F x D ( D IS DISTANCE FROM PIVOT  ! )

for a pivot to be balanced there should be NO RESULTANT MOMENT = ANTI CLOCKISE MOMENT =  CLOCK WISE MOMENT
                                                         NO RESULTANT FORCE  = UPWARD FORCE = DWNWARD FORCE
remember . The longer the distance from the piVOT the less the FORCE IS NEEDED CHECK THE FORUMLA !!

you have to know centre of gravity .
the lower the centre of gravity the more stable / the wider teh base the more stable  of movement


Type of energy

NUCLEAR ENRGY  FISSION AND FUSION .. ENERGY RELEASD BY SUN IS FUSION
KINETIC ENERGY =  Mv^2 / 2 ernegy   
G.P.E= energy of height . Mgh
note
When an object falsl free under graavity its g..e decreases a its getting lower and its K.E is getting faster . The total energy ( KE + GPE ) stays the same since no energy lost AND SO G.P.E AT TOP = K.E AT BOTTOM  ( JUNE 2004 QUESTION 2 )

Strain energy = when someting is bent or strechted ... etc

Effceincy =  Useful Energy out / total enrgy in  X 100% ( JUNE 2008 QUESITON 2 )

WORD DONE = F X D
POWER IS THE RATE OF WORK DONE  THREFORE    POWER - WORK DONW / TIME 
Pressure = FORCE / AREA  ( pascales pa ) or N/m^2

Pressure in liquids : Pgh
pressure acts in all directions and thats why it is  equal around an object.

MANOMETER ( TO MEASURE GAS PRESSURE )  why water is used not mercury ?
BAROMETER ( TO MEASURE AIR PRESUR ) why mercury is use not warer? measured in mm of mercury

SPRINGS .
HOOKE'S  LAW

F= kX

K = SPRING CONSTANT  N/cm

      ^ is defined as how much force is needed to stetch the spring by 1 cm and findng tht u can find all forces and all extensions and work them out .

The law sttes that the extension is directly proportional to the tload . and u can see that from the formula

The spring can extend up to a limit . If more force is appplied the spring breaks . This limit is called elastic limit or limit of proportionality

YOU SHOULD KNO THE EXXTENTIONS OVER FORCE GRAPH

you shuld know how the ticekr timer works

[The Golden Girl =D]

lol thats really encouraging thx

no probs  lol.....nah seriously abt the helpin thing , i am really willing to help (iza fadya )

[Adzel]

• By induction ( complicated process will be studied later ). Pieces of iron( permanent) or steel ( temporary ) become induced magnets when you place them near magnet.

I think its the other way round...

[WARRIOR]

oopsy daizy

[dodi23]

Thanks man!!
ill +rep u in an hour

[J.Darren]

There's gonna be a neutral point between like charges and magnetic poles

CONVENTIONAL CURRENT
Direction of + to - is the same as - to +.

Switches
Transistor can also act as switch.

Difference between EMF and PD

EMF - supplied to the whole circuit.
PD - across a component in the circuit.

CHARGE BY INDUCTION
Towards the very end you should point your finger at the object to compensate for the electron gone in the object (as the object is positively charged at the instance).

DC / AC MOTOR

In DC motor the current is responsible for the turning effect. Whereas in AC you turn the handle manually to induce current.

Using a stronger metal, make the area of the coil larger, increase the number of turns and stronger current (DC) would enhance the output of the motor.

Also a commutator and carbon brush is needed to enable the wire overshoots each other so that the coil can keep on turning.

POWER DISSIPATED

Particularly useful when you are required to measure the power loss in a transmission cable.

I^2 R

SNAIL'S LAW

If you are measuring from a denser to a rarer medium, take the reciprocal of the formula, i.e. (sin r / sin i), bear in mind the the refracted angle must be larger than incidence angle in this case.

[WARRIOR]

lol thanks ill use those when i get to them

+ rep for now

[J.Darren]

Thanks in advance

GRAVITATIONAL PULL

An object with greater volume would encouter more air resistance.

PRESSURE

Force / Area

10 x Density x Depth from surface

Atmospheric pressure - present at all times, 1 x 10^5, a classic question would require you to work out the pressure when at the surface of sea water and when it is few metres below sea level, be sure to include it in your calculation

THERMISTOR

As the temperature increases, the resistance in the thermistor decreases. It is a definiton, as thermistor is made up of semi-conductors.

The lower part of the circuit gets more share of the resistance (note that this part must NOT be connected to a transistor), more current can then flow through it, thus switching on the lamp.

LDR

As the light intensity decreases, the resistance increases.

The part of the circuit with the LDR gets more share of the resistance (note that this part must be connected to a transistor), more current can then flow through it, thus switching on the lamp.

THERMOCOUPLE

Consists of a copper wire, Constantan wire, a hot junction, a cold junction and a digital meter. Due to temperature difference there would be a current flow between the two wires. The greater the temperature differnce, the greater the current. The digital meter converts the current reading into temperature.

MOMENT

The meter rule would only be at equlibrium if net moment = 0 and the experiment obeys the principle of moment.

WAVES

Frequency of the same wave would always be the same, only the wavelength would differ depending on the medium of which it travels in.

Transverse - Particles vibrate perpendicularly to the direction of which the wave travels in.

Longitituional - Particles vibrate in the same direction of which the wave travels in.

BROWNIAN MOTION

Dust particles would randomly collide with air particles, they get suspended in the air. If there is an increase in temperature, Brownian Motion would slow down.

ADVANTAGES OF CONNECTING LAMPS IN PARALLEL

- Even if one lamp goes out, the other remains unaffected as the parallel circuit is still complete.
- Both lamps would glow at normal brightness (i.e. receives full PD from the power supply).

CENTRIPEDAL / CENTRIFUGAL FORCE

Centripedal - the force that is keeping an object in a circular track.

Centrifugal - the force that intends to throw an object off a circular track.

More centripedal force would be needed if the velocity / mass of the object increases.

CONDUCTION

Energetic particles would travel from a hot junction to a cold junction in a material.

HOOKE'S LAW

Force applied is directly proportional to the extension of the spring.

The point when the graph starts to bend is called the extension limit.

The line might break is more force is applied when the spring has already reached the extension limit.

[J.Darren]

TERMINAL VELOCITY

When gravitational pull = air resistance, net force = 0. An object experiencing more resistance would reach terminal velocity faster assuming that the object that it is being compared to has the same mass.