All of AQA PHYSICS Paper 1 in 40 minutes - GCSE Science Revision

Summary

The video is a revision guide for the AQA GCSE Physics Paper 1, covering topics such as energy, electricity, particles, and atomic structure. It is suitable for both higher and foundation tiers, including combined and separate sciences. Key concepts like energy conservation, circuit components, resistance, and the differences between series and parallel circuits are explained. The video also addresses topics like thermal energy, power calculations, and the basic principles of nuclear physics, highlighting the differences between fission and fusion. It provides a fun and fast-paced overview for students preparing for their exams.

Highlights

• Energy is more than just a number; it's a conserved entity in any interaction ⚖️.
• Gravitational potential energy depends on height, measured using 'mgh' 🏔.
• Thermal energy equations help measure kinetic energy gained by particles 🥵.
• Understanding circuit diagrams demystifies electrical concepts less hair-raising! 🔌
• Mastering Ohm's law is vital for calculating resistance and understanding circuits 🧠.

Key Takeaways

• Understanding energy is crucial for physics - it's a conserved quantity that can't be created or destroyed 🍀.
• Energy stores like kinetic, potential, and thermal have specific equations to calculate changes 📚.
• Electricity involves the flow of charge; a good grasp of circuits makes it less shocking ⚡️.
• Nuclear physics involves fission and fusion - one's heavy, the other's about bonding 💥.
• The video is a whirlwind tour but perfect for exam prep and quick revision 📖.

Overview

This rapid revision session kicks off with the basics of energy, emphasizing its role as a conserved, calculative concept in physics. The host explains how energy isn't something tangible but is crucial for understanding the interaction of objects and systems. With a fun narrative, the video covers how energy changes form and about the 'stores' of energy such as kinetic, gravitational potential, and thermal energy.

The sizzle continues with electricity, untangling the often-confusing subject with ease. Key components such as current, voltage, and resistance are detailed using practical examples and immersive storytelling. Formulas to calculate resistance and the description of circuit diagrams are invaluable lessons for anyone looking to demystify this electrifying subject.

The final act dives into nuclear physics, illuminating the differences between nuclear fission and fusion with clarity and enthusiasm. With engaging examples, the video outlines the processes that release energy in nuclear reactions and how they're applied both explosively and for power generation. A lively narrative makes this complex subject accessible and informative.

Chapters

• 00:00 - 00:30: Introduction and Overview The introduction provides an overview of what will be covered in the AQA GCSE physics paper 1. It mentions that this content is relevant for both higher and foundation tier students across double combined trilogy and triple or separate physics. The topics include energy, electricity, particles, and atomic structure, which they refer to as nuclear physics. The speaker assures that they will highlight when a topic is specific to triple physics but not necessarily for higher tier, as the difference is minimal. The pace of the video will be quick, and viewers are advised to pause if they need more time to understand a concept. The section ends with a transition to the topic of energy.
• 00:30 - 10:00: Energy Concepts and Conservation The chapter titled 'Energy Concepts and Conservation' discusses the fundamental idea that energy is not a tangible object but rather a concept or a value that indicates the outcome when objects within a system interact. The chapter emphasizes the law of conservation of energy, which states that energy cannot be created or destroyed. However, energy can be converted into mass, though this is primarily relevant in specific contexts such as nuclear fusion and fission. This conversion does not violate the law since mass-energy equivalence ensures energy conservation. The chapter also refers to different 'stores' of energy, hinting at the diversity of energy forms and manifestations.
• 10:00 - 25:00: Electricity Basics The chapter 'Electricity Basics' initiates with a discussion on energy types, emphasizing the term 'energy stores' as preferred by contemporary examination boards. It notes that energy, measured in Joules, transitions between these stores as objects interact. The chapter introduces various energy stores, notably kinetic energy, explaining that it's calculated using the formula e = 1/2 mv^2, where 'm' is the mass in kilograms and 'v' is velocity. It highlights that an object's kinetic energy increases with its speed. The text hints at further discussions on gravitational potential energy.
• 25:00 - 35:00: Particle Model of Matter The chapter on 'Particle Model of Matter' discusses the concept of gravitational potential energy (GPE). It explains how GPE is calculated using the formula GPE = mgh, where 'm' represents mass, 'g' represents the gravitational field strength (usually either 10 or 9.8 N/kg), and 'h' represents height in meters. The chapter notes that this calculation technically provides the change in GPE, as it is based on the change in height. Additionally, the chapter emphasizes that the higher an object is above ground, the more gravitational potential energy it possesses, and therefore, the more energy it can lose if it falls.
• 35:00 - 60:00: Atomic Structure and Radioactivity The chapter discusses the concept of energy, highlighting an example of potential energy stored in a spring. It introduces an equation to calculate this energy: E = 1/2 * K * e^2, where K is the spring constant (measured in Newtons per meter) and e is the extension (measured in meters). This equation describes how much energy is stored when a spring is stretched from its original length. Additionally, the chapter covers thermal energy and how changes in thermal energy can be calculated. The specific heat capacity (SHC) equation is introduced, which is used to determine the change in thermal energy. This equation is written as E = m * SHC * ΔT, where m represents mass, SHC is the specific heat capacity, and ΔT is the change in temperature (measured in degrees Celsius). The chapter also introduces the idea of representing changes with symbols such as Δ (the delta symbol) to signify 'change in' a particular variable.
• 60:00 - 67:00: Nuclear Fission and Fusion The chapter begins with a discussion on specific heat capacity, a measure of how much energy is needed to increase the temperature of 1 kilogram of a substance by 1° Celsius. This concept is crucial as it explains how thermal energy causes particles in a substance to move faster, thereby gaining kinetic energy. More detailed discussions on kinetic energy and particle movement will be covered in the particles topic. The chapter notes that sound or vibrational energy is not a focus in this context.
• 67:00 - 67:30: Conclusion and Invitation for Feedback The chapter "Conclusion and Invitation for Feedback" concludes by focusing on the fundamental concepts of energy transfer and conservation within systems. It reflects on how energy, in various forms like kinetic or chemical potential energy, plays a crucial role in system dynamics. The chapter briefly touches upon the idea that energy must always be transferred between objects or storage mechanisms for any activity or change to occur within a system. Importantly, it emphasizes that in a closed system, energy is conserved and not lost to the surroundings. This summary provides a general overview, lacking specific equations or detailed chemical processes, suggesting that these elements are more relevant to chemistry.

All of AQA PHYSICS Paper 1 in 40 minutes - GCSE Science Revision Transcription

• 00:00 - 00:30 let's see how quickly we can cover everything you need to know for AQA GCSE physics paper 1 this is good for High room Foundation Tier double combined Trilogy and triple or separate physics that's topics 1 to four that's energy electricity particles and atomic structure but I like to call it Nuclear Physics I'll tell you when something is just for triple but not when something's just for higher tier because to be honest there's not a lot of difference at all we're going to be belting it here so pause the video if you need a bit more time to get your head around something you see let's go energy isn't
• 00:30 - 01:00 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 in topic four when it comes to nuclear fision and fusion there are what some people call different stores of energy normal people
• 01:00 - 01:30 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 * mass in kilog time speed or velocity squared the faster an object goes the more kinetic energy it has gravitational potential
• 01:30 - 02:00 energy or 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 change in height the higher off the ground on object is the more gpe it has or rather the more GP it has available to lose if it falls to the ground at last potential
• 02:00 - 02:30 energy is what we find in say a spring this is given by eal half K e^2 that's half time the spring constant in Newtons per meter sometimes called stiffness times extension in met 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 De C in Syle form that's eal MC Delta Del T that Delta Rod triangle
• 02:30 - 03:00 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° celus 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
• 03:00 - 03:30 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
• 03:30 - 04:00 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 rolled 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
• 04:00 - 04:30 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
• 04:30 - 05:00 we double 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 short cut with the whole GP to K
• 05:00 - 05:30 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 hand side multipli together in Brackets you could get a situation where for for example
• 05:30 - 06:00 the roller coaster 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 used 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
• 06:00 - 06:30 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 ameter 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
• 06:30 - 07:00 and then we pop 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
• 07:00 - 07:30 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 it 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 to divided by the total energy in it
• 07:30 - 08:00 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
• 08:00 - 08:30 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 and 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 from in the world
• 08:30 - 09:00 around us 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 light energy into
• 09:00 - 09:30 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 burned to produce energy 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
• 09:30 - 10:00 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 potenti potential energy when connected in a
• 10:00 - 10:30 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 ER all the energy to the bulb as this is
• 10:30 - 11:00 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 of charge similar to moles in chemistry it's just a specific number but we don't care what the number in a Kum is potential difference PD for short
• 11:00 - 11:30 also known as voltage but AQA don't like 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 Jew 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 component you want to
• 11:30 - 12:00 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 Vols but we don't care about minuses really really when it comes to PD we
• 12:00 - 12:30 only care about the number here's the equation for PD PD in Vols is equal to energy in Jews ided by charging 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 eal QV on your formula sheet current on the other hand tells us what the rate of flow of charge is essentially how fast is charge flowing through a circuit or a component
• 12:30 - 13:00 like any equation for a rate as per usual it's something divided by time so here it's current in amps equals charge in kums divided by 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 Q equal i t that's I * T we
• 13:00 - 13:30 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 it if we make a circuit
• 13:30 - 14:00 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 steeper the gradient of
• 14:00 - 14:30 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 Ohm's law so R is equal to v/ I for a resistor you'll end up with the same answer no matter what point you
• 14:30 - 15:00 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 non ohic 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 p and higher current the
• 15:00 - 15:30 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
• 15:30 - 16:00 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 as an aside AQA of royy messed up lately in their exams whereby they've asked the question what would happen to a resistor if the temperature increased to which the mark scheme says that its resistance would increase it would act like a metal they are wrong resistors are specially made from specific material such that their resistance stays constant even if
• 16:00 - 16:30 the temperature changes if that wasn't the case we wouldn't get this straight line for a resistor and we might as well just use Metals instead silly AQA now there is another component called a diode it will give you this graph the circus 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 and LED is a light emitting diode similar symbol just
• 16:30 - 17:00 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
• 17:00 - 17:30 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 a 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 that up let's deal with that first
• 17:30 - 18:00 point if these resistors are the same let's say 10 ohms each then that 6 Vols 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
• 18:00 - 18:30 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 Oh'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 the second resistor too is there also a second
• 18:30 - 19:00 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 2 volts we could then use OHS 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 Oh'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
• 19:00 - 19:30 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 given 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
• 19:30 - 20:00 flowing through the battery and 0.2 amps of that is flowing through the top resistor that must mean that there's 0.3 amp 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's resistance decreases if the
• 20:00 - 20:30 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 Vol meter 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
• 20:30 - 21:00 goes down resistance of the ldr goes up as does its share withth of voltage this could then be connected in some way to the light bulb so it turns on as it gets dark we know from earlier 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 times current moreover if we substitute Ohm's LW into this we swap the V for I R and we end up with the alternative equation p = i * I * r
• 21:00 - 21:30 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 AQA these days have an obsession with calling it direct PD which is pointless but 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 D in the circuits in your home the neutral wire
• 21:30 - 22:00 stays at a potential 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 htz 50 times a second if you 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 what doesn't change in the cas of DC of course in a socket the
• 22:00 - 22:30 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
• 22:30 - 23:00 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 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 main what fuse would it need
• 23:00 - 23:30 well we know power is 800 wat we know PD or 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 ID 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
• 23:30 - 24:00 stations cables and more that transmit it 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
• 24:00 - 24:30 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
• 24:30 - 25:00 the last bit of electricity is just for 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 IE both positive or both Negative they repel each other instead if you touch a vandergraph generator
• 25:00 - 25:30 electrons are taken from 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 size 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
• 25:30 - 26:00 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 vandergraft 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 particles next or the particle model of matter density tells you how compact mass is for a
• 26:00 - 26:30 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 meter 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 particles make up the object and also how tightly packed together they we know water vapor is less dense than liquid water because
• 26:30 - 27:00 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
• 27:00 - 27:30 likely just be 1 mm so you could use verer 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 Bar Fall to the brim displacing the same volume of water as
• 27:30 - 28:00 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 beforehand 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 with the molecules are still touching but free to move past each other and gas
• 28:00 - 28:30 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 it its temperature will remain constant until it's all melted only then
• 28:30 - 29:00 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
• 29:00 - 29:30 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
• 29:30 - 30:00 equation specific lacenter 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 jewles per kogam that means the equation for energy needed to change state is this eal 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
• 30:00 - 30:30 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
• 30:30 - 31:00 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 p2v2 afterwards we know volume is measured in me cubed but pressure is measured in Newtons per met squar but we also call this pascals PA for short finishing off with atomic structure but to be honest it's really all about nuclear I so I like calling it Nuclear Physics now you should remember this
• 31:00 - 31:30 first bit from chemistry paper one the idea of what atoms are like came about gradually JJ Thompson discovered that atoms are made up of positive and negative charges he came up with the plum pudding model of the atom a positive charge with lots of little electrons dotted around it it was Ernest Rutherford who found out that the positive part of the atom must be incredibly small We Now call this the nucleus and the electrons must orbit relatively far away from it Neil's B later discovered that electrons exist in shells or orbitals then James Chadwick discovered that the nucleus must also
• 31:30 - 32:00 contain some neutral charges he called them neutrons while the positive charges are called protons different types of atoms are represented by symbols which we also find in the periodic table the bottom number is the atomic number thus the number of protons in the nucleus this is what determines what element you actually have the top number is the mass number this tells you how many protons and neutrons are in the nucleus so that must mean that this carbon atom has six neutrons on top of it six protons to make 12 however you can get a car atom with seven neutrons instead so its mass
• 32:00 - 32:30 is 13 these are isotopes atoms of the same element but different numbers of neutrons the term radiation means any particle or wave that's emitted by something the electromagnetic spectrum is all radiation but they're all emitted by electrons all apart from gamma radiation that is gamma radiation is actually emitted by the nucleus of an atom if it has excess energy it's getting rid of gamma rays are high energy em Wes they can be dangerous as they can ionize atoms if absorbed by them knocking electrons off this can
• 32:30 - 33:00 cause damage to the cells in your body and also cause cancer but there are two other types of radiation nuclei can emit too but these are actual particles and they're emitted when nuclei Decay change isotopes with more neutrons are generally more unstable and likely to Decay heavier nuclei like amorium 241 Decay by what we call alpha decay to become more stable the nucleus will emit a bundle of two protons and two neutrons what we can just call an alpha particle this is Alpha radiation this is what the
• 33:00 - 33:30 nuclear decay equation would look like for this to show that the nucleus is decayed into two parts the alpha particle which must have an atomic number of Two and a mass of four and the daughter nucleus that's just the nucleous left over which of course is no longer going to be amorium as it's lost protons to go from an atomic number of 95 to 93 turns out that's neptunium but you'll never have to remember these you just need to worry about the numbers it's just maths 9 5 goes to 93 + 2 and
• 33:30 - 34:00 the mass is similar 241 goes to 237 and 4 there is actually a nucleus that has the numbers two and four it's a helium nucleus you do need to know that but AQA also say that you should write he instead of an alpha symbol in a decay equation I much prefer saying Alpha but you should get the mark either way lighter Isotopes lighter nuclei like carbon 14 Decay by Beta Decay or beta Decay instead what happens is that a neutron in the nucleus turns into a proton and an electron but the fast
• 34:00 - 34:30 moving electron that's ejected by the nucleus escapes and we now call this beta radiation the mass of an electron is basically zero so we put that on top it has the opposite charge to a proton so we say it has an atomic number of minus one now be careful here 6 goes to what + -1 no it's not five It's s 6 is equal to 7 + -1 like we said a neutron has turned into a proton so the nucleus has gained a proton it's gone from six to seven the mass however is unchanged
• 34:30 - 35:00 so it's still 14 once again AQA like you to put e for an electron instead of a beta symbol but they'll allow both alpha particles are massive and have a relatively large charge so as they travel they knock loads of electrons of loads of atoms in their way we say they have a high ionizing ability or high ionizing power but as a result they're stopped easily they're absorbed by a few centimeters of air or just a piece of paper if you have a Giger mude a GM tube touching a source of alpha radiation
• 35:00 - 35:30 like amarium it will detect the alpha radiation emitted move it a bit further away or stick a piece of paper between and the radiation counts per second will fall to zero or near zero anyway I say near zero because there are background sources of radiation from the world around us raidon gas comes out of concrete and rocks that's slightly radioactive cosmic rays from space are also background radiation man-made radiation like that from nuclear weapons contribute to it too so if you want an accurate radiation count over a minute from an alpha Source say you should do a
• 35:30 - 36:00 background count first then take that number away from the count with the source that will give you a corrected count Alpha radiation can be useful however it's used in smoke detectors beta radiation is not as ionizing as Alpha but it has higher penetrating power it's fairly good at both it can pass through more air and a piece of paper easily but it's absorbed by a few millimeters of aluminium it can be used to detect thickness of thin materials like paper when made in a mill gamma radiation has low ionizing ability so
• 36:00 - 36:30 why is it so dangerous well it's because it can actually get to you technically there's nothing that can completely stop gamma radiation but lead and concrete can reduce the intensity of it by absorbing some of it gamma has many uses actually it can be used for radiotherapy or gamma knife surgery to kill cancer tumors in your brain for example and it can be used to sterilize medical equipment as it kills any microbes on the scalpel Etc radioactivity is the rate of decay of a source of Alpha Beta or gamma now you know not really Decay
• 36:30 - 37:00 with gamma but the same idea this rate can be measured with a GM tube like we said and we can calculate it by doing radiation count divided by time in seconds this gives you the radio activity sometimes just called activity in counts per second which is also called Beckel BQ for short over time the number of unstable nuclei in a sample or Source decreases as they're decaying into something else so that means the activity decreases too half life is what we call the time it takes for both of
• 37:00 - 37:30 these to half actually it also goes for Mass too the half life of a radioactive isotope could be days months even millions of years long if we draw a graph to show how activity changes over time it might look something like this how do we find the half life well we take the initial number half it then draw a line to the curve to see how long that took what's interesting is that if we do the same again it will take the same amount of time to half it doesn't matter how much of the isotope you have or when you start timing it will always take the same amount of time to half you
• 37:30 - 38:00 could be asked to calculate half life let's say that we have a sample that started at 96 Beckel activity and it fell to 12 Beckel after 1 year 12 months the question you always have to ask is how many half lives you don't do 96 / by 12 but instead count how many times you have to half it to get to the second number one half life 48 Beckel two half lives 24 three Half Lives 12 it took three Half Lives to decrease to 12 Beckel so if 12 months is three half
• 38:00 - 38:30 lives that must mean that one half life is a third of that 12 divid by 3 the halflife is 4 months just some triple stuff to finish off if you take a nucleus like uranium 235 and fire a neutron at it that Neutron will be absorbed and will make the nucleus more unstable instead of decaying by alpha or beta it actually splits in half producing two similar daughter nuclei this is nuclear fision what's weird though is that the total mass of the products of this vision is less than
• 38:30 - 39:00 what we had to begin with how's that possible well it turns out that mass can turn into energy in these situations yes we say that energy can't be created or destroyed but at this level we say that the reactants have mass energy to get around that the energy produced is thermal or more accurately kinetic as we talked about earlier the clever thing is is that this fion also releases up to three more neutrons that can go off and cause more fion in other nuclei themselves and so on and and more energy is released we now have a chain reaction
• 39:00 - 39:30 left unchecked this can go out of control that's what an atomic or nuclear bomb is however if you control this chain reaction in a nuclear reactor you can produce a consistently safe and huge amount of energy that can be used to then produce electricity by heating steam to turn a turbine connected to a generator Etc Fusion however is what happens in the Sun to produce energy from Mass two light nuclei like hydrogen Fus together into one heavier one helium in this case and energy is released but only if they have a lot of kinetic
• 39:30 - 40:00 energy to begin with but hang on how can both fion and fusion result in energy being released well it's all to do with what nuclei you have to begin with if you want to know more about this do a level physics or watch my binding energy video scientists have been trying to make fusion reactors for decades but they haven't managed to make one where they're able to harness enough energy from the radiation released from the process for it to be viable and that's it hopefully this has been useful leave a like if it has and and leave any comments or questions you have below and hey come back here after the exam to let
• 40:00 - 40:30 us all know how you got on we'd love to know click on a card to go to the playlist for all six papers and I'll see you next time best of luck