let's see how quickly we can cover what you need to know for edexel GCSE physics paper 2 this is good for double combined and triple or separate science and high in Foundation tier that's topics 8 to 15 energy forces electricity magnetism and particles but Ed XL split everything up in a weird way so I'm going to mix things up to save some time I'll tell you when some of the bigger concepts are just for triple but not for higher and Foundation tier as there's not a lot of difference to be honest we're really going to be moving here so pause the video if you need a bit more time to get your head around something you see energy isn't something you can hold in your hand it's just an idea it's a number that tells us what will happen when objects interact in what we call a system total energy in any interaction is always conserved energy cannot be created or destroyed now there is a small caveat with that as energy can be turned into matter Mass but it's still technically true the whole Mass to energy thing is only important for triple people when it comes to nuclear fision and fusion there are what some people call different stores of energy normal people just say types of energy but these days the exam boards are obsessed with the word stores so that's what we're going to have to use the energy in these energy stores changes when objects interact energy is measured in Jewels an object can have energy in the following stores kinetic energy we calculate it with e = half mv^ 2 half time mass in kilog time speed or velocity squared the faster an object goes the more kinetic energy it has gravitational potential energy or G GP for short we calculate that by eal MGH that's mass time gravitational field strength either 10 or 9.8 in Newtons per kilogram you'll be given it in any question that involves it Times by height in meters technically this only gives you a change in gpe as the H here should really be changing height the higher off the ground an object is the more gpe it has or rather the more GP it has available to lose if it falls to the ground elastic potential energy is what we find in say a spring this is given by E = half K e^2 that's half time the spring constant in Newtons per meter sometimes called stiffness times extension in me squar that's how much further the spring has stretched from its original length thermal energy or change in thermal energy is calculated with the shc equation energy equals mass time shc * temperature change in deg C in Syle form that's e equal MC delta T that Delta or triangle just means change in that's change in temperature here shc is short for specific heat capacity this tells you how much energy is needed to raise 1 kilogram of a substance by 1° C it's different for every material out there remember that an increase in thermal energy results in particles moving faster so this is essentially a way of measuring the kinetic energy gained by particles in a substance more on this in the particles topic we don't really talk about sound or vibrational energy as this is just particles moving so in reality it's kinetic again chemical potential energy say in food or fuels there's no equation for that and that's more chemistry's remit but you might have to mention at some point that these two things do have a store of chemical potential energy in order for anything to happen in a system energy must be transferred from one object to another or one store to another store in a closed system no energy is lost to the surroundings no energy in from the surroundings either which allows us to equate two lots of energy that just means saying that two lots of energy are the same for example a roller coaster car teetering at the top of a ride just has gpe gravitational potential energy basically zero kinetic energy as it starts to roll down gpe is turned into K okay I should probably say that it gpe store is decreasing while its K store is increasing instead but all that really matters is that at the bottom it's lost that gpe using this height here so we can say gpe lost equals K gained gpe equals K so if it had this many jewels of gpe at the top it must have the same number of jewels of K at the bottom we can then rearrange the K equation to find its speed for example I always recommend rearranging equations using symbols not words so here I want to make V the subject leave it by itself so to move something from one side of an equation to the other we just do the opposite with it to get rid of the half we double the the other side then to get rid of the mass from the right hand side well we're multiplying by it on the right so we just divide by it on the left finally to get rid of the square on the V we square root the other side so speed V is equal to 2 * the kinetic energy divided by the mass or square rooted then just pop in your numbers punch it into your calculator and boom you got your answer you could also equate elastic potential energy and kinetic energy say if a toy car is pulled back on a spring and let go there is a shortcut with the whole GP to K scenario by the way if we just equate the two equations you'll notice that mass m is on both sides so they actually cancel out so rearranging this we find that V is equal to the < TK of 2 g h so really we only need to know the height from which something Falls in order to know its speed at the bottom if you have to rearrange the GP equation just remember that the two things you have to move from the right hand side have to go on the bottom of the left time side multiplied together in Brackets you could get a situation where for example the roller coaster has has more GP at the top than k at the bottom where's the rest of the energy gone you might ask well it must have been lost to the surroundings so that means it cannot be a closed system this could be due to work done against air resistance or friction work is just another word for energy Ed by the way this really does belong in the particles topic but for some reason it's here so we're going to cover it now it's the specific heat capacity practical we can find the specific heat capacity of a material by heating it up and measuring the change in its temperature for example we can use an electric heater that slots into cylinders made of different Metals we turn the heater on use a voltmeter to measure the PD and Amer to measure the current and we multiply these to get power more on this later by the way we use a balance to measure the mass of the block we use a timer and a thermometer to measure how much the temperature of the block has increased by in a certain time say 60 seconds we take the power and we multiply it by the time to get the energy that's gone into the block and then we po these numbers into our rearranged shc equation the issue is that while heating some energy will be transferred to the surroundings which means that the temperature change that we measure will be less than what it should be so invariably our final value for the sa will be higher than the True Value power is just the rate of energy transferred any rate is a change in something divided by time here's the equation P equal e / T the unit for power is W for Watts but this is just the same as jewels per second so my laptop has a 200 watt power supply which just means that it uses 200 jewles of energy every second to find out how much energy uses in a minute we just rearrange this equation so e is equal to P * T this is how you'll see it in your formula sheet by the way efficiency is a measure of how much energy going into a system is used usefully it's just a ratio or a fraction so we calculate it by doing the bit divided by the lot so in this case it's the useful energy out divided by the total energy in it also works with power too let's say that my power supply only supplies 120 wats of useful power to the laptop even though it uses 200 so its efficiency is 120 / 200 which is 0.6 as a decimal multiply that by 100 to turn it into a percentage and that means that it's 60% efficient you could be asked to give efficiency as a decimal or a percentage that means that 40% of the power or energy in is wasted this is usually as heat lost to the surroundings as usual if houses or other buildings don't have sufficient insulation a lot of heat can be lost through walls Windows Doors and the roof Etc just for triple real quick we can do a practical on this by wrapping up cans with different insulating materials or different thicknesses of the same material pouring in hot water from a kettle in measuring the temperature after a certain amount of time the higher the temperature is at the end the better the insulation energy sources are not the same as energy stores rather energy sources are where we harness energy from in the world around finite or non-renewable sources include fossil fuels like coal oil and gas all burn to create heat for example in electrical power stations finite means that once used up no more can be obtained nuclear fuel like uranium is also finite although would not run out for a very long time renewable sources include wind power hydroelectric power stations both of these are used to turn generators to generate electricity solar panels convert light energy into electricity directly geothermal power stations involve water being pumped deep underground to be heated and biofuel is the term for any biological matter that's burn to produce energy a force is any push or pull forces can be contact forces that's when objects are physically touching like when you push a door or they can be non- contct like magnetism electrostatic forces and gravity This Is A New Concept in gcsc physics and shocker it's a silly one because even contact forces are due to the electrostatic repulsion between electrons in your skin and the door for example but whatever technically pushing a door involves a normal contact force while other contact forces could be friction air resistance and tension the important thing is that we can represent forces with vectors that is an arrow that shows the direction and magnitude of the force the magnitude is the size of the force and that's indicated by the length of the arrow if two forces act on an object there's a resultant Force we find this by technically adding the vectors however if they're going in opposite directions one must be negative so in this case the resultant force would be 3 Newtons to the right and that's positive if we've decided that positive is in the right direction if vectors are at right angles to each other you use Pythagoras to find the resultant this works because you can make a triangle by moving one of the forces you could also be expected to use trig that's Soaker TOA to find either one of these angles Chan of is going to be tan you use if any if forces are balanced that is they add up to zero that means that the object will not accelerate it won't change change velocity no that doesn't necessarily mean it's not moving it just stays at a constant velocity and that could be 0 m/ second of course this is Newton's first law of motion by the way more on those in a bit if a measurement or quantity just has magnitude but no direction it's not a vector but it's called a scalar instead here are some examples of both note that displacement is distance traveled with a direction while similarly velocity is the vector form of speed weight is another name for the force due to gravity that acts on an object is calculated by multiplying the mass in kilograms by gravitational field strength or G which here on Earth is 9.8 Newtons per kilogram sometimes we just round that to 10 though you'll be told which to use in a question that means that 1 kgam of Mass on Earth has a weight of 10 Newtons now if you hold an object up with your hand you must be pushing up with a force that is equal to its weight in order for the forces to be balanced and so it doesn't accelerate however that means that if you lift it upwards at a constant speed that's also true that's something that people of and forget to lift something at a constant speed you must be lifting with a force that's the same as the weight we can therefore then calculate the energy that is used to lift this object using the equation for work done that's work done equals force time distance moved work done is just a fancy term for energy transferred by a force this equation is true for any situation but in this case the force is the weight and the distance is the height so we could say the gain in energy is equal to mass * G * H does that look for familiar it should because that's the exact same equation for calculating gravitational potential energy that's GP gained to be precise forces can also deform an object if you pull on a spring that is fixed at one end it will stretch or extend hooks law states that FAL K that's Force equals spring constant sometimes called stiffness times extension the unit for spring constant is Newton per meter this works for any object that stretches elastically that is returns to its original shape once the force is removed it can also be true if an object is compressed instead we can see that as K is a constant force and extension are directly proportional that means whatever happens to one happens to the other double the force double the extension you can hang varying masses off a spring and measure the extension and you'll end up with a straight line that goes through the origin 0 0 and that proves this directly proportional relationship if you carry out this experiment just make sure your ruler zero Mark is lined up with the bottom of the spring that way you can be sure your only measuring extension rather than the length of the whole spring that would introduce a systematic error if you did that by mistake also make sure you're at ey level with the bottom of the spring when measuring against the ruler to avoid Parallax error and that is a random error rather than a systematic error the energy stored in the spring is equal to half k^ squ something was attached to the spring and you let go the object would gain the same amount of kinetic energy at least in an ideal or closed system that is no energy is lost of the surroundings due to heat for example just just for Triple A Moment is a turning Force for example what you do with a spanner this is equal to force times distance to the pivot so the unit just ends up being newton meters note that this looks similar to the work done equation but this force and distance here are perpendicular to each other rather than parallel similarly to just normal forces if the moments turning clockwise are equal or balanced with the moments turning anticlockwise the object will not turn that is if it wasn't turning to begin with we can call this the principle of Moments by the way an application of moments is Gears a small gear can turn a large gear in order to increase the moment produced you can think of pressure as being how concentrated a forces is the equation is pressure is equal to force ided by area so the unit for pressure is Newtons per meter squared but we can also call this unit pascals or PA for short you probably know the deeper you go underwater the greater the pressure and this is due to the weight of the water above your head pushing down on you we can calculate this pressure using p = h row that's just a Greek letter time g h being height of the water column above you basically depth times density times gravitational field strength the density of water is 1,000 kg per me cubed for gas pressure in paper to all you need to know is that it's due to the collisions of the gas particles with surfaces and you can hopefully remember from paper one that you can increase this by adding more gas reducing the volume or raising the temperature which makes the particles move faster well three of these result in the collisions occurring more frequently while increasing the temperature also means that the particles have more kinetic energy so they collide with the walls with more momentum therefore exerting a greater force the higher your altitude the less dense the atmosphere becomes due to there being fewer particles in any given volume hence pressure also decreases electricity is one of those topics that people find confusing so let's try and demystify it shall we electricity is the flow of charge or charges like electrons they carry energy from a source of energy to a component where the energy is released as another type of energy here's a simple circuit we have a cell here this is the symbol for that this is the symbol for a battery that's just several cells connected in line we draw straight lines for the wires which in this case are going to a lamp a light bulb and that lights up of course you have to have complete Loops of components and wires in order for these charges to flow by the way you're going to see me mix up cells and batteries in this video because they're just the same thing really and they do the same job leave an angry comment below if you're really that mad about it so what's going on here in this circuit then the battery has a store of chemical potential energy when connected in a complete circuit this energy is transferred to the electrons which move through the wires this movement of charge is called a current and we say it always goes from the positive terminal of the battery to the negative don't think about it too much as the electrons pass through the bulb their energy is converted into light and some heat too probably as they're never 100% efficient this light and heat is then transferred to the surroundings including your eyes so you can see it but the electrons don't just disappear once they transfer all the energy to the bulb as this is one big loop these electrons are pushed back round to the battery by the ones behind them where they're refilled with energy ready for another trip around the circuit this constant flow of electrons transferring energy is what keeps the light bulb on because electrons are so small and there are so darn many of them we don't deal with individual electrons but instead deal in kums of electrons or kums of charge similar to moles in chemistry it's just a specific number but we don't care what the number number in a Kum is potential difference PD for short also known as voltage tells us how much energy is transferred per Kum of electrons so if a cell or battery says it's one volt that means that one Jewel of energy is given to every Kum of electrons that pass through it if a battery is 6 volts that means six Jews is supplied per Kum instead we measure PD with a voltmeter voltmeters always get added last to a circuit as they're always connected in parallel to the components you want to measure the voltage of in the real world that means the leads or cables from the voltmeter always Peggy back into other leads if we put the voltmeter across the battery it should measure 6 volts right because 6 volts is supplied to the electrons in the circuit that's just 6 Jews per Kum but put it across the bulb and it should still say 6 Vols why because the electrons have to lose all of that 6 volts worth of energy as they pass through okay it might be minus 6 volts but we don't care about minuses really when it comes to PD we only care about the number here's the equation for PD PD in volts is equal to energy in Jews divided by charge in kums in simple form V is equal to e over or divided by q q is the symbol for charge but it's measured in C in kums you'll see the rearranged version e equal QV on your formula sheet current on the other hand tells us what the rate of flow of charges essentially how fast is charge flowing through a circuit or a component like the equation for a rate as per usual it's something divided by time so here it's current in amps equals charge in kums / time in seconds or i = q / T yes we use capital i as the symbol for current not C blame the French for that as they called current intensit cant it does mean though that we don't get confused between current and kums though so we stick with it you're going to see the rearranged version of this equation on your formula sheet qal i t that's I * t we measure current with an ameter note that it's not amp meter unlike a voltmeter it must go in series that means in line with the component we want to measure the current for components in a circuit have resistance that is they resist the flow of charge or current through them but that's not a bad thing this has to happen in order for them to work a bulb has resistance which causes energy to be transferred and light to be emitted a resistor of course has resistance too but it just produces heat when current flows through it if we make a circuit with with a resistor and change the PD available to it what we find is that an increasing PD results in a greater current flowing in fact doubling one doubles the other so we can say that PD and current or V and I are directly proportional drawing a graph of these two makes a straight line and if we turn the battery round we can get Negative values for both two but still a straight line through the origin this straight line a constant gradient shows that a resistor has constant resistance we say it's omic the Ste deer the gradient of this line the lower the resistance of the resistor as more current is Flowing per volt the equation for resistance is ohms law V equal I that's PD in volts equals current in amps time resistance in ohms that's the unit for resistance we can get the resistance of a component from an IV graph like this by just picking a point on the line and rearranging ohms law so R is equal to v/ I for a resistor you'll end up with the same answer no matter what point you pick if you repeat the same experiment for a bulb in place of the resistor however you'll end up with a curved graph like this this shows that the resistance is changing the resistance of the metal filament in the bulb in fact you'll find that any metal has a changing resistance if you increase the PD and current they're nonic at higher PDS the current increases less and less so that means they can't be proportional this shows that the resistance of the metal is increasing with a higher PD and higher current the change in gradient shows us that this is true but we still just take a point on the line and use 's law if we want to find the resistance it's just that it does matter where you pick that point in this case so why does resistance change for a metal well it's because Metals consist of a lattice or grid of ions surrounded by a sea of delocalized electrons that just means they're free and free to move or rather they're fairly free to move because they do collide with the ions as they flow that's why the metal heats up when you pass a current through it the higher the current the more frequent these collisions are this makes the ions vibrate more and more which in turn makes it harder for the electrons to flow the resistance has increased now there is another component called a diode it will give you this graph the circuit symbol might give you a clue as to why this is a diode only lets current flow through in One Direction we say that in One Direction the resistance is very high and it's very low in the other which is why the current increases Suddenly at around 1 volt an LED is a light emitting diode similar symbol just with a couple of extra bits these are what most lights in electronics are these days rather than filament lamps they act in the same way as a diode so they give you the same graph but they just happen to emit light as well we can do another practical on Resistance by measuring V and I for a length of metal wire connected to a circuit with crocodile Clips to calculate resistance of the wire using Ohm's law then we can move One Clip further up the wire to see how the length of this wire affects resistance you should end up with a straight line through the origin showing that resistance and length of wire are directly proportional series and parallel circuits this is where things get a bit tricky remembering what happens to current PD and resistance when we have components in series or in parallel here's the simplest series circuit we can make really just two resistors in line with the battery what you need to remember is that for components in series total PD is shared between them current is the same for all of them and the total resistance is just the sum of all resistances that just means added up let's deal with that first point if these resistors are the same let's say 10 ohms each then that 6vs total PD from the battery must be shared between them so if we put a voltmeter across each of these they'd both read 3 volts it wouldn't matter what resistance these resistors are they could be a million ohms each if they're the same then that total PD is shared equally by the time the electrons leave the second resistor they have to have lost all six volts worth of energy ready to go back to the battery to be refilled by the way we can also call this setup a potential divider circuit as the total potential total PD is being shared if the resistors don't have the same resistance then we can use the second point to help us that is the current is the same for both let's say the first resistor is 20 ohms using four volts of the total six volts available we know two things out of v i and r so let's use Ohm's law to find out the third for it current in this case I rearranging Oh's law we get I is equal to V / R so that's 4 ID 20 0.2 amps same for the second resistance resistor to is there also a second thing we know about the other resistor why yes there is remembering the first rule up here we know that if the first resistor is using four volts of the total six volts available well then the other resistor must be using up two volts we could then use 's lore again to find its resistance 10 ohms the rule of thumb is this the greater the resistance the greater the share of the total PD it gets we can also use 's law for a whole circuit we just need to make sure that we're dealing with the total PD total current and total resistance the rules for parallel circuits are the opposite the PD is the same for every Branch current is shared between each branch and the more resistors you add in parallel the lower the total resistance this by the way is because you're giving the current more roots to move through the circuit which means more current can flow so if these two resistors are connected to the 6volt battery in parallel you know straight away that the PD for both has to be 6 Vols voltage isn't shared in parallel circuits if however we say 0.5 amps total current is flowing through the battery and 0.2 amps of that is flowing through the top resistor that must mean that there's 0.3 amps flowing through the bottom resistor if you're not in a rush why not pause the video and see if you can calculate these two resistances by the way if you want a little bit more help on this then have a look at my video how to answer any electricity question it's not only metals that can change resistance we can have a thermister and you have a circuit that responds to changes in temperature a therm M's resistance decreases if the temperature increases so in essence it does the opposite to a metal in this case if the temperature increased the resistance of the thermister would go down as does its share of the total PD that means the PD measured by this voltmeter will increase this could be the basis of a temperature sensor for your central heating for example an ldr is a light dependent resistor very similar to a thermister but resistance goes down with increased light intensity not temperature so this circuit could be on the top of a street lamp light intensity goes down resistance of the ldr goes up as does its share with of voltage this could then be connected in some way to the light bulb so it turns on as it gets dark we know that power is the rate of energy transferred so energy divided by time however when it comes to electricity we can also calculate it with this equation too P equal VI power equals voltage PD time current moreover if we substitute Ohm's LW into this we swap the V for ir and we end with the alternative equation p = i * I * r or p = i^ 2 R the electricity that comes out of a battery is DC or direct current that's current that only Flows In One Direction direct PD means the same thing direct PD is a potential difference that is only in One Direction and this results in direct current Main's electricity that comes out of your socket is AC alternating current resulting from an alternating PD in the circuits in your home the neutral wire stays at a potential of of 0 volts while the Live Wire well its potential varies but it averages out to an equivalent of 230 volts so we say this is Main's voltage or Main's PD this alternating PD causes current to go back and forth at a frequency of 50 HZ 50 times a second if we hooked up a battery and Main's electricity to an oscilloscope we'd see these two traces to see how the PD changes over time or doesn't change in the case of DC of course in a socket the wire with blue insulation around it is the neutral wire while Brown is the Live Wire the third yellow and green wire is the earth wire and that's connected to the pin at the top it's not necessary to complete the circuit and there should be no current flowing through it normally it's a safety wire that's connected to the outside of metal appliances like kettles or toasters so if anything goes wrong with the other wires inside of the kettle current will flow through it to the ground instead of through a person if they touch it which would give them an electric shock also in a plug a fuse is attached to the live wire which is designed to melt or blow if the current exceeds a certain number of amps usually 3 5 or 13 amps if something goes wrong in an appliance the current May well Spike so the fuse will blow before too much damage can be done to it or the user you may need to use P equal VI to calculate the normal operating current for an appliance to deduce what fuse should be used in the plug let's say that a microwave draws 800 WS of power from the mains what fuse would it need well we know power is 800 WS we know PD or vol voltage is 230 volts because it's Mains so we use P equals IV to find the current rearrange it current is equal to P / V that's 800 divided by 230 that gives us 3.5 amps we can't use a 3 amp fuse otherwise it would just blow under normal operation so we go for the next one up a 5 amp fuse a 13 amp fuse would work as well but the current would have to increase to that before it blows and that could be more dangerous electricity is supplied to homes and businesses by the National Grid a network of power stations cables and more that transmit it acoss across the country the current produced by a power station is quite large so much so that if it went straight into the overhead cables you see above you when you're out and about a huge amount of energy would be lost as heat due to the resistance of the cables to reduce this energy lost Transformers are used triple people you'll need to know exactly how they work for paper 2 but for now we all just need to know what they achieve a stepup Transformer outside the power station increases the transmission voltage to over 100,000 volts as P equals VI and power stays roughly the same in this process if PD goes up current must decrease as a result this decrease in current means less energy and power is lost due to Heating and we can see this from the other power equation p = i^2 r lower the I lower the P lost of course having such a high voltage going into homes would be dangerous and unnecessary so we have a Step Down Transformer nearby to reduce it down back to a more safe 230 volts the last bit of electricity is just for trip triple if insulating materials that is materials that aren't good conductors are rubbed against each other electrons are transferred from one to the other the object electrons are removed from is left positively charged as electrons are negative themselves and the object they're added to is now negatively charged oppositely charged objects attract each other positive and negative if they have like charge that just means the same charge I.E both positive or both Negative they repel each other instead if you touch a vandergraph generator electrons are taken from every every part of your body including your hair leaving all of you positively charged your positive head repels your positive hairs and the hairs also repel each other too two objects with different Siz charges produce an electric field between them we can't see this field but we can represent it by drawing lines the arrows on the line show the direction of the field and that's always positive to negative they show the direction of electrostatic force exerted on a positive charge if we put one in the field the space between if we put a negative charge in there instead it would move in the opposite direction to the field lines which makes sense because it would be attracted to the positive object even a single object that is charged creates a field for example this is what the field around the vandergraph generator would look like this is called a radial field by the way as the lines are diverging getting further apart the further you go from the ball this shows that the strength of the electric field gets weaker with distance magnetism and electromagnetism a permanent magnet is a metal in which the molecules are permanently aligned mind in such a way that they produce a magnetic field which can exert a force on particles in other objects and also electrons we give the two ends of a magnet the names North and South Pole short for North facing and south facing poles because that's the way they would point to line up with the Earth's magnetic field so if we made it float you can use iron filings or mini compasses placed around a magnet to visualize its magnetic field magnetic field lines are always complete Loops even though we don't draw them inside the magnet and they never touch these ones going out the ends here will eventually loop back around if we carried on drawing them the direction of magnetic field lines is always from North Pole to South Pole an induced magnet is a material usually a metal whose particles align temporarily when placed in a magnetic field so it makes its own magnetic field hence why an iron nail can be attracted to both the North or South Pole of a permanent magnet we say iron is magnetic but it is not a magnet Cobalt and nickel are also magnetic copper and aluminium for example are not bring two permanent magnets together and they will attract if opposite poles are facing and they repel if like poles are facing a current flowing through a wire will produce its own magnetic field we draw the field lines as concentric circles around it using our right hand to help us remember which way the field goes we use the letter B as a shorthand for a magnetic field by the way as well as in the equation coming up the motor effect is when such a wire is in another magnetic field and it will experience a force the equation is f Bill where f is force I is current in amps L is length of the wire in the magnetic field and B is the magnetic flux density essentially the magnetic field strength this is measured in Tesla note that this equation only works as it is if the current and magnetic field lines are perpendicular to each other but maybe it is worth remembering that if the wire is parallel to the fuel lines it will experience no Force to find out the direction of the force however on The Wire we use Fleming's left hand rule your thumb is force first finger is field middle finger is current make a juny gun with them where they're all perpendicular and Bam freeze FBI just twist your wrist to line up your fingers with the current and the field always North Pole to South Pole and the way that your thumb is pointing is the direction of the force on the wire in this case upwards to measure the size of the force in reality we can put the magnet on a balance due to Newton's Third Law the magnet will also be pushed down with the same Force calculate the force from the fake mass measured us an ameter to get the current and a ruler to measure the length of the wire and boom you can calculate the magnetic flux density between the poles of your magnet electric motors of course employ the motor effect by using a coil of wire that experiences opposite forces on both sides causing it to turn however the current must be reversed every half a turn otherwise it would just stop at the vertical position in this case so that's why we have what we call a split ring commutator to reverse the current every half a turn to make a motor turn faster you can increase the current use a stronger Magnet or add more turns to the coil so there's a greater length of wire ultimately experiencing the force a loudspeaker is in essence just a motor that goes back and for instead of round and round the varying current due to the signal from the music play say will cause the coil to vibrate back and for and that's attached to the speaker cone which then produces sound waves in the air double people you're actually done but don't forget to leave a like before you leave yeah a magnet will cause a current carrying wire to move but the opposite is also true a wire that's moved through a magnetic field will result in a current being induced in it the electrons will move to be more precise we should say a potential is induced in it essentially voltage this can be called the Dynamo or generator effect a generator itself looks like a motor urn the coil and a potential will be induced in the coil this is basically how power stations work the steam made from burning fuels or nuclear fision turns the turbine which turns this coil as you can see we don't need a split ring commutator it still works all that it means is that it's an alternating PD that's produced or alternating current AC to increase the output of a Dynamo or generator just turn it faster or similar to a motor add more turns to the coil or use a stronger magnet I say turn it faster but it's not easy you see the current induced in the coil also produces its own magnetic field and this opposes the turning that led to it being produced to begin with so that's why it requires energy to keep it turning and that makes sense you can't just start it turning and then it just carry on otherwise that would mean you'd be getting energy for nothing but in other words this means that induced currents or potentials don't like being made some dynamos have a split ring commutator or circuitry such that they produce DC instead of AC it will be lumpy DC though similar to a loud speaker being a back and forth motor a microphone is a back and forth generator sound waves move the diaphragm back and forth which is attached to a coil that moves back and for around a magnet and that then induces a potential in the coil that signal then travels through the wires to the phone recorder or whatever Transformers are used in the National Grid to change the voltage at which the electricity is transmitted through the overhead cables the current from a power station is so high that too much energy would be lost due to the resistance in the cables if it just went straight into them therefore A Step up Transformer increases the voltage before it enters the grid this then reduces the current so less energy is lost due to heating the reason one goes up while the other one goes down is because electrical power is equal to voltage or PD * current V * I in an Ideal World the power in and out of a transformer should be the same that would mean that it's 100% efficient so V and I are inversely proportional we can therefore say that V * I for the primary coil is equal to V * I for the secondary coil this is the basic makeup of a transformer the primary coil is connected to the power station in this case the secondary coil is connected to the overhead cables there are more turns on the secondary coil which means it's a stepup Transformer the voltage will increase the current will decrease the cars are wrapped around a soft iron core get this into your head right now though there is or should be no electricity or current in the core instead the electricity is wirelessly transmitted from one coil to the other how is this well it's because the alternating current in the primary coil produces its own magnetic field and the iron core acts like a guide for it we use ion by the way as it's easily magnetized and demagnetized it works well as a guide this magnetic field then induces a voltage and current in the secondary coil in order for a current to be induced though a wire must experience a change in the magnetic field which is why we must use a if we use DC in the primary call it would make a magnetic field but it would be static which cannot induce a current in the secondary coil the ratio of turns in the coils is equal to the ratio of the voltages if the secondary coil has double the turns it has double the voltage and therefore half the current so we can say NP / NS equals VP / vs you can also flip the whole thing when it comes to rearranging it to find VSS or NS the Step Down Transformer at the other end of the cables steps the voltage back down to a safer PD of 230 volts which means it must have fewer turns on on the secondary coil particles next or the particle model of matter density tells you how compact mass is for a material or object for example a cup of iron has a much higher mass than a cup of cream showing that iron has a higher density but we don't measure density in kilog per cup but kilog per M cubed so the equation is this density is equal to mass divided by volume the symbol we use for density is the Greek letter row it's just a p without the ear on it density is dependent on what part particles make up the object and also how tightly packed together they are we know water vapor is less dense than liquid water because even though both made from water molecules they're more spread out when a gas so there are fewer of them in every Meer cubed finding the density of a regular object that is an object with a volume that can be calculated using its Dimensions is easy for example the volume of a cuboid a rectangular object can be calculated by multiplying the length of its three sides and then we just pop it on a balance to get its mass and then use the equation to find the density for Dimensions that are a few millimeters in length a ruler won't be that accurate as its resolution will likely just be 1 mm so you could use verier calipers instead they usually have a resolution of 0.1 mm a tenth of a millimeter objects that are very very thin like wires need a micrometer instead they usually have a resolution of 0.01 mm or 100th of a millimeter the volume of an irregular object like a chest piece for example cannot be calculated from measurements instead we use a displacement can also called a Eureka can after the Greek philosopher Archimedes got into a bath full to the brim displacing the same volume of water as his volume tie thin string around the object and gently lower it until it's just under the water line and wait for the water to stop dripping out into the beaker that you hopefully put there beforeand we decant this water collected into a measuring cylinder to get the volume of water displaced and therefore the volume of the object solid liquid and gas are the three main states of matter for example water can be ice a solid where the particles vibrate around fixed positions it can also be water where the molecules are still touching but free to move past each other and gas water vapor where the particles are far apart and moving randomly which is why it can be compressed while solids and liquids cannot to melt a solid or evaporate a liquid you must supply energy usually in the form of heat to overcome the electrostatic forces of attraction between the particles if you have a block of ice and Supply heat to it its temperature will increase the particles vibrate faster which means they're gaining kinetic energy however once it reaches the melting point of 0° C its temperature will remain constant until it's all melted only then will its temperature start increasing again the same thing happens when it reaches 100° and it turns into a gas but why the constant temperature after all energy is still going into the ice but during a change of state the particles don't gain kinetic energy but rather potential energy we say that any substance has internal energy that's the sum of the kinetic energy and potential energy of all particles in a substance you need to know this definition only one of these can change at a time an increase in temperature means we must have an increase in kinetic energy of the particles while a change in state when heating anyway must mean an increase in potential energy we have equations for both of these energy changes we saw at the start the equation for increase in thermal energy which was eal MC delta T mass time shc time change in temperature we now know that this is only for an increase in kinetic energy of particles in a substance when there's a change in temperature during a change of state the temperature stays constant so we can't use the specific heat capacity equation instead we use the slh equation specific lent heat slh of a substance tells you how much energy is needed to change the state of 1 kilogram of it for example the slh of fusion that just means melting or freezing for water to ice is 334,000 Jews per kilogram that means the equation for energy needed to change state is this e equal ml energy equals mass in kilog times specific latent heat in Jews per kilogram we know gases consist of particles that are far apart moving fast and randomly if you heat the gas the particles gain kinetic energy and they move faster this means that they collide with the walls of the container the gases in with a greater force and more frequently which results in an increased pressure pushing outwards just for triple you also need to know that you can also increase the pressure by compressing a gas to do this you need to exert a force inwards on the gas we also say that this is doing work on the gas you also need to know what happens if a gas is at a constant temperature in this case pressure times volume is equal to a constant that means that if P or V goes up the other one goes down that means p and v are inversely proportional one doubles the other one halves we can therefore say that P1 V1 that's the pressure and volume before the change is equal to P2 V2 afterwards we know volume is measured in me cubed but pressure is measured in Newtons per me squared but we also call this pascals PA for short and that's it hopefully this has been useful leave a like if it has and leave any comments or questions you have below and hey come back here after the exam to let us all know how you got on we'd love to know