Let’s try and get our head around heat and temperature. A concept we thought at least this one we understood and then our Physics teacher took that away from us as well didn’t they??

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What is temperature

Some time ago we started to notice that things changed when it got hot or cold. Specifically, we noticed that matter (a sciency word for ‘stuff’) got bigger, or expanded, when it was hot and got smaller, or contracted when it was cold. Some clever scientists used this idea to invent various thermometers and then marked numbers on it so that we could actually measure how hot or cold something is. You know us humans always like measuring…

Now, we may not have understood how these thermometers did what they did, and I’m sure many of you never gave it much thought. If it’s hot or cold, the thermometer says so. But, how does it do that? If I search ‘thermometer’ on the internet and choose ‘images’, I mostly get images like the one you see here. These are not the only thermometers, but we will stick to this design for now. The first thermometer actually used air instead which expanded in heat and contracted in cold, but it was not as accurate as liquid and so thermometers started to use liquids soon after and we stuck to that.

The particle model of matter

When it gets hotter, the liquid expands inside the thin glass tube and so rises up. But why?

The basic reason is that the particles in the liquid move faster and move greater differences because they now have more energy. This causes them to spread out a little bit. This can be a little confusing because we learn pretty early on that liquids cannot be compressed and have a constant volume, but this is only at a constant temperature.

The above paragraph only makes sense if you are happy with the idea that matter is made out of particles. We have all seen the diagram below many times by now I’m sure, but we never actually see these particles our science teachers assure us are around do we? Well, they do exist, I am quite sure. This idea of matter being made out of particles is known as the particle model of matter.

UNCERTAINTIES IN PHYSICS

A new definition of temperature

So now we have an understanding of how our thermometer works, we could say that temperature is a measure of how fast the particles are moving, or even a measure of the average kinetic energy of the particles. If you give the particles energy they move more quickly and so take up more space, which is why the liquid in a thermometer rises! Here is a simulation of a thermometer which you can play with and see the particles in it moving around.

So, if temperature is how quickly things are moving, at zero temperature they should… erm… not be moving?? But that can’t be right, I’ve walked around at 0°C and was able to breathe the air and survive. If particles had stopped moving, the air should have not been in a gaseous form, it should have been solid and the particles should not have even been vibrating! And what the heck would negative temperatures be? Well… Not all temperature scales start at the same place.

We chose to put 0°C at the freezing point of water and 100°C at the boiling point of water which is useful for many purposes, but is not exactly correct when we think of our new definition of temperature is it? We need a new scale!

Enter Kelvin!

Here he is. Looking rather sleepy in this photo, but he’s no doubt been hard at work coming up with a new scale for temperature! What do we call this new scale? The Kelvin scale!

What happens at zero kelvin? Nothing! Nothing moves. Particles in a solid do not even vibrate! We call this point absolute zero but… It turns out that it is impossible to actually reach this point.

That shouldn’t stop us from defining it though. It is impossible to get anything to actually sit still for a moment! I know that feeling…

Ok, so is heat the same as temperature??

Erm… Not really. If you think of how the two words are used, heat is something which something has or something which we can give to something. We do say ‘heat up’ as well, but that really means the same thing as to give something more heat so as it now has more heat in it.

Temperature, on the other hand, is a measure of how hot or cold it is. So, when we give something ‘heat’, what are we actually giving? Well… energy, right? So, heat is the energy we give it and temperature is the measure of average kinetic energy of the particles. Now it’s sounding like the same thing again! Not exactly… The keyword here is average. I mean the average kinetic energy of each particle.

However, if we give something energy, it should get hotter. Pretty straight forward right? However, if you plot a graph of heat against temperature something strange happens. I will have to leave that for another blog post though I’m afraid!

PHYSICS PRACTICE QUESTIONS – WHY ARE THEY SO ESSENTIAL?

A bit about the author, Paul H:

Paul is a qualified and experienced Physics, Maths, and Science teacher, now working as a full-time tutor, providing online tuition using a variety of hi-tech resources to provide engaging and interesting lessons.  He covers Physics, Chemistry, Biology, and Science from Prep and Key Stage 3 through to GCSE and IGCSE. He also teaches Physics, Maths, and Chemistry to A-Level across all the major Exam Boards.

You can enquire about tutoring with Paul here

The post Heat and Temperature: An Introduction appeared first on The Tutor Team.

The atom and its nucleus

In this picture of an atom, we can see we have protons and neutrons in the centre of the atom, which make up the nucleus and we have electrons around the nucleus. If I was teaching Chemistry right now, I might ask you what element it is in, and where it is in the periodic table. But I’m not (carbon, group 4, period 2). In fact, Chemistry is mostly concerned with the electrons in the atom as they are what is responsible for the chemical reactions it undergoes. Nuclear physics is concerned with… the nucleus of course!

The word atom comes from the Greek word atomos, which means indivisible. In other words, it cannot be divided into smaller bits. It has been theorised for a long time that matter is made out of indivisible particles and we called them atoms for that reason. However, once we found them and gave them the name we annoyingly found that they could be divided into further little particles, which can be called ‘subatomic particles’ and so atoms should really be called something else, but the name stuck.

The above atom is carbon because of its protons, nothing else. If we were to change the amount of neutrons or electrons it would not change the fact that it was carbon. Carbon is, by definition, an atom (or ion) with 6 protons.

9  THINGS TO ASK A PRIVATE TUTOR – BEFORE YOU BOOK THEM

Isotopes

As I said, we could change the number of electrons or neutrons, but it would still be carbon. Changing the number of electrons makes it a positive or negative ion, but changing the number of neutrons would change it into a different type of carbon, or a different isotope of carbon. Not all carbon atoms have 6 neutrons. Some have 7 and some have 8. But by far the most common isotope of carbon is the one with 6 neutrons. The one with 8 neutrons does something quite strange…

UNCERTAINTIES IN PHYSICS

Nuclear decay

This can also be called radioactive decay. If left alone for a long time, (5730 years), there is a 50% chance that it would have changed, as if by magic, into an entirely different atom. It is important to understand here that nothing was done to encourage this. It did not react with anything. Heating up, cooling it down, shaking it or shouting at it will not speed up this process, slow it down or stop it. It can not be predicted when it will happen, only a probability like above can be stated.

Below is something called a nuclear equation of the process.

As you can see, before the decay there is the carbon-14 nucleus and after a nitrogen-14 nucleus. Looking more closely at the carbon 14 nucleus we can see that they have labelled one of the blue circles as a neutron and that same circle on the right is now red and labelled a proton.

A quick look at the periodic table tells us that nitrogen does in fact have 7 protons and this isotope of nitrogen has a mass of 14 and so it must have 7 neutrons. So, during the decay the number of protons went up by 1 and the neutrons went down by 1, leaving the mass number unchanged. Nothing was added to the nucleus and so clearly…

… a neutron changed into a proton??

Yup. That is what happened. Weird right? This type of decay is called beta decay and it is not the only one. There are also alpha decay and gamma decay. If you are studying A-level Physics, this is beta negative decay; there is also beta positive decay.

ISN’T IT AMAZING THAT WE’RE ALIVE? (A BRIEF GUIDE TO ORGAN SYSTEMS)

Ok, so what about these keywords?

So, let’s use this example decay to define the words:

• Nuclear/radioactive decay – This is the process which we have just been describing. An atom starts off as one type of atom and changes into another type of atom. It is spontaneous and random.
• Nuclear radiation – This is what is given off in the process. In this case an electron is given off, and we call this the beta particle. There are also alpha particles and gamma rays. These are examples of nuclear radiation as it is given off in nuclear decay. The antineutrino  is also given off in this example, but we only talk about that at A-level.
• Radioactivity – This is simply the topic of all of this. It can also be a word to describe how much radiation something emits. We can measure the activity of a radioactive isotope which means how often one of the atoms decay and emit some radiation.

Ok. I hope that is clear enough now. Thanks for reading and I shall see you in the next post!

A bit about the author, Paul H:

Paul is a qualified and experienced Physics, Maths, and Science teacher, now working as a full-time tutor, providing online tuition using a variety of hi-tech resources to provide engaging and interesting lessons.  He covers Physics, Chemistry, Biology, and Science from Prep and Key Stage 3 through to GCSE and IGCSE. He also teaches Physics, Maths, and Chemistry to A-Level across all the major Exam Boards.

You can enquire about tutoring with Paul here

The post Radioactivity, nuclear decay, radiation… What’s the difference? appeared first on The Tutor Team.

Spotting the difference

So, firstly the difference. How can I tell if I am looking at a series circuit or a parallel circuit?

Well, many of you might be able to tell me that in the pictures above, the one on the left is a parallel circuit and the one on the right is a series circuit. That would be right. But why? You might say that it is because on the left you can see many of the wires are in parallel, but that would be a mistake. Occasionally an exam question might try and catch you out with an oddly drawn circuit like the ones below. (Incidentally, I made this circuit with a very good online electrical circuit simulator which you can find here.)

The circuit on the left is actually a series circuit. The reason it is a series circuit is because if you imagine being an electron leaving the battery at the top, you would only have one route to go and you would find yourself going through all 3 of the lightbulbs. The one on the right is a parallel circuit despite no wires being parallel to each other. A parallel circuit has junctions a series circuit does not. A junction is a place where the current can split up. Some of the current goes one way, some goes another. In the two examples of parallel circuits above, an electron would leave a battery and then go through one light bulb. However, they have a choice which one they go through and maybe next time around they’ll go through a different one.

ELECTRICAL RESISTANCE AND OHM’S LAW

Voltage and current in series and parallel circuits

So, if voltage is the amount of energy per charge then in parallel each electron would have a lot more energy to use up on one lightbulb because they only go through one lightbulb before going back to the battery to get more energy, whereas in the two series circuits they need to share that energy across all 3 light bulbs before they get back to the battery. You’ll notice that light bulbs in series circuits, therefore, are a lot dimmer than in parallel circuits. Also, if you use a 12 volt battery, the three lightbulbs in series will share the voltage so as they add up.

In the circuit on the left 12V = 4V + 4V +4V. I will sum up all of these in equations at the end.

If you measure the current in a series circuit, you will find it is the same everywhere. It might be a good idea to use the simulation to follow along here and perform your own experiments so as you can see what I mean.

7 WAYS TO GET THE BEST RESULTS FROM PRIVATE TUTORING

Voltage and current in parallel circuits

Using the simulation, have a go at making the circuit below. Do you notice anything about the currents shown in the ammeters A1 to A4? Now try measuring the voltage across each lightbulb and across the battery.

What you should find is that the voltage across each light bulb is the same as across the battery. This is because each electron uses all of its energy from the battery on that single light bulb and then goes back to get more. You should also find that the current splits up so as if you added up the current in A2, A3 and A4 they would come up the value in A1. This is because current is a measure of how much charge flows by a point per second. Well, the charge was split up at the junctions, and so it makes sense that if you added up A2 to A4 they would give you the value of A1.

Resistors in series and parallel

We know that resistors reduce the amount of current that flows through something. If there is more resistance, the current goes down. More specifically, the resistance in ohms is a measure of what voltage would be required to produce a current of one amp. So, without any more help, see if you can answer these questions:

1. Looking at the set ups on the right, can you place them in order of resistance. Lowest first, highest last.
2. Can you give the value of the overall resistance of set up B and C?

Resistors as Checkout Counters

Most people guess that B has the highest resistance, but then get a bit stuck. This is because they think, ‘Well I can see that two resistors in parallel wouldn’t be as hard to get through as two in series, but there are still two resistors, so that must have a higher resistance than just one resistor.’ But, think about it in a different way: Imagine the resistor is a checkout counter in a supermarket. Clearly if I opened up another checkout counter (in parallel), it would speed up the flow of customers. In fact, it would double the flow and so would half the resistance

Ok, once again I am over my word limit, so I am afraid I shall have to leave it there. I hope you found it helpful. I think the next post I write is going to be about how we use waves to make sense of the world ‘out there’!

A bit about the author, Paul H:

Paul is a qualified and experienced Physics, Maths, and Science teacher, now working as a full-time tutor, providing online tuition using a variety of hi-tech resources to provide engaging and interesting lessons.  He covers Physics, Chemistry, Biology, and Science from Prep and Key Stage 3 through to GCSE and IGCSE, plus teaches Physics, Maths, and Chemistry to A-Level across all the major Exam Boards.

You can enquire about tutoring with Paul here

The post Series and parallel circuits appeared first on The Tutor Team.

Uncertainties questions in physics are almost always in the context of a practical, and they tend to follow a similar format each time they appear. This means you can learn a method to answer the questions and apply it each time.

Why do we need to think about uncertainties?

There will be uncertainty in any reading, and we can say ‘every measurement has inherent uncertainty’. Often measurements are written with the uncertainty provided and an example of this would be to write a voltage in this sort of format: 5.60 ± 0.005 V.

They are essential to consider the reliability of your experiment, and in industry or academia a piece of work would be rejected if you didn’t give the uncertainty in your readings. It is important for finding the highest and lowest possible values, which are needed to give clear analysis, ensure safety in say an engineering build or to demonstrate the reliability of your results.

PHYSICS PRACTICE QUESTIONS – WHY ARE THEY SO ESSENTIAL?

How do we calculate uncertainties?

Uncertainties in equipment are down to the precision of the instrument’s manufacture. The uncertainty in a measurement using a particular instrument is no smaller than plus or minus half of the smallest division. For example, a temperature measured with a standard thermometer would be reported as having an uncertainty of ±0.5 °C if the graduations are 1 °C apart.

Take care with rulers, because measuring lengths is one of the most common practical skills. For rulers we must include two uncertainties because there are two ends at which there could be an error. The first is at the zero end, and the second in reading off the value.

As both ends of the ruler have a ±0.5 scale division uncertainty, the measurement will have an uncertainty of ±1 division. Therefore, for most rulers, this will mean that the uncertainty in a measurement of length will be ±1 mm.

We also have to consider errors due to other factors, not just the precision of the instrument. These can be due to human reaction time, for example in using a stopwatch, or due to a property of the measured item. For example, a wire being measure may have bumps in it, and so the length will have some uncertainty. For these, we would generally reduce the number of reported significant figures.

HOW TO REVISE: 5 STUDY TIPS THAT REALLY WORK

Absolute and Percentage Uncertainties

You also need to be able to switch between absolute and percentage uncertainties. The percentage uncertainty in a measurement can be calculated using:

and for a repeated measurement

Combining Uncertainties

We also need to be able to combine uncertainties. How you do this depends on the equation related to the experiment you are undertaking.

• If the equation is in the form a = b + c then you should add the absolute
• When the equation is in the form a = b × c or a = b ÷ c then you should add the percentage uncertainties and then find the absolute uncertainty.
• If the equation is in the format a = b^c then you should multiply the percentage uncertainty by the power (value of c).

We need both absolute and percentage uncertainty because absolute uncertainty allows us to calculate the upper and lower bounds of the reading. Percentage uncertainty allows us to combine uncertainties in different units e.g. we may do an experiment where we want to calculate the velocity from a distance and a time:

If our results are

displacement = 0.7 ± 0.001 m

time = 1.4 ± 0.1 s

Then velocity =   = 0.5 m s^–1

Then to find the uncertainty we should add the percentage uncertainties because we cannot add metres and seconds together.

For the displacement: = 0.14 %

For the time: = 7.14 %

Therefore, percentage uncertainty in velocity = 7.14 + 0.14 % = 7.28%

Absolute uncertainty in velocity =

Therefore, our final answer would be given as

Velocity = 0.5 ± 0.04 m s^–1

EXAM ANXIETY: HOW TO KEEP CALM DURING EXAMS

Calculating uncertainty in a gradient

To find the uncertainty in a gradient then we need to draw two possible lines on the graph. A line of best fit, an also a line of ‘worst’ fit: the shallowest or steepest line of fit from the data. You then find the gradient of each line.

The percentage uncertainty is calculated using:

NOTE: The value should always be positive, and so modulus bars rather than a bracket are used in the equation.

How can we reduce uncertainties?

1. Take repeated measurements. Then the uncertainty in this value can be estimated as half the range of obtained values

For example:

Range of values = 7.82 – 7.78 s = 0.04 s

Half the range = 0.02 s

Therefore, mean time = 7.8 ± 0.02 s

2. Use multiple instances of readings. For example, measure 10 pendulum oscillations and then the mean time for one oscillation. This reduces the uncertainty by a factor of 10:

Conclusion

In this blog, we have considered

• estimating uncertainties in measurements
• reducing uncertainties
• combining uncertainties
• the difference between absolute and percentage uncertainty
• calculating uncertainties from graphs

Questions for practice can be found in specimen and past papers. Good questions to get you started are:

• AQA Specimen Set 1: Paper 3 Question 1
• Edexcel June 2009: Unit 3 Question 5
• AQA June 2017: Paper 3 Question 1

You will need all these skills in your practical activities and in your exams! Good Luck!

A bit about the author, Joanna P:

As a fully qualified teacher of Physics with 10 years teaching and tutoring experience including as Head of Department in a very successful Independent Girls’ School, Joanna’s undergraduate degree was in Natural Sciences from Gonville and Caius College, University of Cambridge, and her MSc in Education was from Loughborough University.

An experienced 1-2-1 tutor and examiner for Edexcel, Joanna has as excellent track record of results in my students including improved grades up to three times above their university predictions from school. She is also a Fellow of the Chartered College of Teaching and a Chartered Science Teacher, sitting on the Education Group for the Association for Science Education and serving as Regional Secretary for the East Midlands, showing her commitment to exceptional physics and science teaching practice.

You can enquire about tutoring with Joanna here

The post Uncertainties in Physics appeared first on The Tutor Team.

In my last post, I wrote about a fairly extensive piece on charge, current, and voltage in electricity. I said some things have something called charge and some things do not. Like charges repel, opposite charges attract. Electrons all have negative charges and so repel each other, but would be attracted to protons that have positive charges. I said that current is the rate of flow of charge, in other words: how much charge flows by in a certain time; and that voltage is the amount of energy per charge. In this post, I shall be focusing on electrical resistance and the topic known as Ohm’s law

Relating current to voltage

So, if voltage is the energy per charge and current is how quickly the charge is flowing, it stands to reason that the more energy I give the electrons, the faster they will flow right? Right.

That’s basically what happens. You increase the voltage and the current also increases. Now, if the two are directly proportional, we say they are following a law called Ohm’s law. If current and voltage interact in this way within a component, the component is an ohmic conductor.

What does directly proportional mean? It means that if one doubles, then so does the other. If one triples/halves/quadruples…. so does the other. It does not mean that if one goes up by 5, for example, so does the other. The relationship is related to ratios and the change must be multiple. If you were to plot current against the other, you would get a straight line that goes through the origin.

Not all components follow ohm’s law. Wires and resistors do (to a point), light bulbs and diodes do not.

V= voltage

I – current (obvs!)

HOW TO WRITE GOOD PHYSICS COURSEWORK – A TEACHER’S GUIDE

Resisting the flow

So, what is it that determines the gradient (steepness) of the line on ohmic conductors? Well in the graph above of the ohmic conductor, A steep line would mean only a small voltage would lead to a high current, and a gentle gradient would mean the opposite. So, if a larger voltage is required to produce the same current, then something must be resisting the current… ELECTRICAL RESISTANCE!

You may have the idea that resistance is a measure of how difficult it is for 

electric current to flow through it. That’s right. Resistance is measured in ohms, which uses the Greek letter ‘omega’, Ω as its symbol. If a component has a resistance of one ohm, then that would mean one volt of voltage would be required to produce a current of one amp going through it. So, voltage is providing the charge energy, that energy causes the charge to flow and the rate at which it flows is called current, and finally, the resistance is a measure of how much voltage is required to produce a particular current.

So, depending on how confident you are with your Maths you might be able to work out the equation for resistance…

R = resistance (Ω)

V = voltage (V)

I = current (A)

This can be rearranged using a formula triangle as shown below:

Warning! V=IR is not Ohm’s law!

Returning to Ohm’s law for a moment, we learned that if something follows Ohm’s law then voltage and current are directly proportional to each other. This can be written as:

I ∝ V

 This means that voltage would be equal to current multiplied by some constant. Now that we have learned about resistance, we see the constant that relates the two is resistance.

V = IR

… and so this means that we can calculate the resistance of a wire or resistor from the gradient of the line as shown on these two graphs.

WHAT IS ELECTRICITY?

But…

…. And it’s a big but…. V = IR is not Ohm’s law! Search online and it says it is everywhere, but it’s not, trust me. V=IR is just a formula which relates voltage, current and resistance. Ohm’s law states that current is directly proportional to voltage. You can use the V=IR formula on any component whether it follows Ohm’s law or not! If something follows Ohm’s law this would mean that the resistance is constant because of the gradient of the line is constant (ie. The line is straight), but if the resistance is not constant, you can still use the formula V=IR to work out these variables.

Applying V=IR to non-ohmic conductors

 To emphasise the point made in the previous paragraph, let us consider the V-I graph of a filament light bulb:

Voltage is on the x-axis and current is on the y-axis. As voltage increases, the gradient decreases. This would mean that for higher voltages, a larger increase in voltage. I’ve added some made-up numbers and zoomed in to show it more clearly below:

As you increase the voltage from 0V to 1V, you get an increase in current of about 1.5A, but later on, increasing the voltage from 3V to 4V only gets an increase of less than 0.5A. So, the resistance has increased. We can still calculate the resistance using the formula V=IR though, even if this is not following Ohm’s law, the resistance changes, which is why the gradient of the line changes.

Ok, that’s it for this post. I shall write another one soon on series and parallel circuits and that will probably wrap it up for this series on electricity. Hope you have found it helpful!

A bit about the author, Paul H:

Paul is a qualified and experienced Physics, Maths, and Science teacher, now working as a full-time tutor, providing online tuition using a variety of hi-tech resources to provide engaging and interesting lessons.  He covers Physics, Chemistry, Biology, and Science from Prep and Key Stage 3 through to GCSE and IGCSE, plus teaches Physics, Maths, and Chemistry to A-Level across all the major Exam Boards.

You can enquire about tutoring with Paul here

The post Electrical resistance and Ohm’s law appeared first on The Tutor Team.

Chances are, if you’re studying Physics A-level or GCSE you’ve been set work that includes previous exam questions or specific targeted practice of the concept you learnt that day.

So why are practice questions essential in Physics?

It’s simple. Physics practice questions reinforce your knowledge by testing your recall and embed understanding by allowing you to apply your skills and knowledge. It’s sometimes called ‘shed loads of practice’ or SLoP and there are lots of excellent resources out there to help you prepare for your exams with practice questions.

Types of questions

We can divide the Physics content up into different styles of question. Firstly you have the single-answer question, multiple choice, or match up the answer. These you simply need to recall information to answer correctly. Completing multiple practice recall tasks will drill these into you and hopefully mean these are easy marks to obtain. By practicing this recall, you become faster and more efficient, and are more likely to get the marks!

Then we have written questions which include tasks such as asking you to recall knowledge or explain a phenomenon, or perhaps design an experiment. And finally, we have mathematical or formula-based questions which ask you to recall or use physical formulae to arrive at a numerical answer.

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Why Practice Short and Longer Answer Questions?

Physics questions may employ simple recall of one word or phrase, or longer explanations. There are also 6 mark explanations for some exam boards or tasks which require you to write a plan for an experiment.

Learning the material can be done in lots of ways, including retrieval practice, use of knowledge organisers, and flashcards as examples. However, it is vital to practice these style questions so you are familiar with how the exam board wants you to phrase the answer. Therefore, finding previous exam questions from your exam board is the best way to ensure you are primed to gain maximum marks.

Different Exam Boards

Each board has a unique style. Some will expect experiment design to be written in a particular way, for example including ways to minimise errors. Other exam boards will expect a greater emphasis on how to interpret the data. Some will expect more flowing prose whereas some are happier with bullet point answers. It’s important to use the short and long answer questions from previous papers to ensure you are confident with the style required.

These are similar style questions from the AQA GCSE specification and the Edexcel IGCSE specification:

	Question	Answer
AQA June 2018 Paper 1	A student wanted to determine the density of a small piece of rock.   Describe how the student could measure the volume of the piece of rock.   [4 marks]	Level 2: The method would lead to the production of a valid outcome. Key steps are identified and logically sequenced. Level 1: The method would not necessarily lead to a valid outcome. Some relevant steps are identified, but links are not made clear. No Relevant Content. Indicative Content: part fill a measuring cylinder with water measure initial volume place object in water measure final volume volume of object = final volume – original volume   fill a displacement / eureka can with water water level with spout place object in water collect displaced water measuring cylinder used to determine volume of displaced water
Edexcel June 2019 Paper 1	A student investigates how current varies with voltage for a metal filament lamp.   Describe a method the student could use for their investigation.   [4 marks]

Familiarise yourself with mark schemes

As you can see, the style of marking is quite different. The AQA question requires a valid method in a logical sequence. The IGCSE separates each marking point independently. Knowing the style of answer you are expected to give is extremely important to being able to give an answer that will obtain maximum marks!

Through completing lots of past paper questions you will also become familiar with these mark schemes, and know what sort of answer they are looking for. Consequently, you will be more prepared for your exams.

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Why Practice Mathematical Questions?

The other sort of common question in Physics is the mathematical style question. With these mathematical questions it’s easy to see why we need to utilise practice tasks. They enable you to become familiar with rearranging equations, substituting numbers correctly and understanding significant figures and rounding, therefore, the more practice questions you complete, the more confident you will be with tackling these questions in the exams.

Familiarity with the maths skills is essential to both pace and accuracy in exams, and repeating similar questions can drill the expectations into you. This hopefully makes the exams a little less daunting! Many physics concepts are underpinned by mathematics. Subsequently, being confident with the formulae can help you to understand what’s going on with the physics.

Some Examples

For example, consider the idea of Hooke’s Law. This is a simple equation

force = spring constant x extension

Being able to rearrange this and use it to find any missing component is important. For example we can rearrange this equation to find the extension of a spring with known spring constant under a given force (up to the limit of proportionality).

extension = force/(spring constant)

Let us take another example, the more complicated equation of gravitational force

F=G (m_1 m_2)/r^2

Here the rearrangement is not so simple, for example to find r:

r=√(F/(Gm_1 m_2 ))

Completing plenty of practice questions, which ask you to find different missing values, subsequently allows you to become an expert in rearranging each type of equation.

Calculator Comfort

Secondly, practicing our mathematical equations allows you to be comfortable with how your calculator works, therefore, I would highly recommend a Casio scientific calculator, as this will do everything you need. I’ve used the same calculator throughout school, university and now in my teaching career!

Whichever choice you make, it is really important to be familiar with the nuances of how the calculator works. Key things to discover and practice are:

• Using standard form
• How to convert fractions to decimals (in physics you should always give your answer as a decimal to an appropriate number of significant figures)
• Using trigonometric functions
• Changing from degrees to radians (A level)
• How to input
• How to square and cube numbers, and how to find square and cube roots.
• What order to input things in order to generate the correct value

All of these things are important, and practice will enable you to successfully navigate these using your own calculator.

Summary

In conclusion, I hope I have opened your eyes to some of the ways in which using practice questions can help you prepare for your exams. As well as embedding knowledge they can also help you understand the exam board expectations and even help you with using your calculator!

A bit about the author, Joanna P:

As a fully qualified teacher of Physics with 10 years teaching and tutoring experience including as Head of Department in a very successful Independent Girls’ School, Joanna’s undergraduate degree was in Natural Sciences from Gonville and Caius College, University of Cambridge, and her MSc in Education was from Loughborough University.

An experienced 1-2-1 tutor and examiner for Edexcel, Joanna has as excellent track record of results in my students including improved grades up to three times above their university predictions from school. She is also a Fellow of the Chartered College of Teaching and a Chartered Science Teacher, sitting on the Education Group for the Association for Science Education and serving as Regional Secretary for the East Midlands, showing her commitment to exceptional physics and science teaching practice.

You can enquire about tutoring with Joanna here

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A lot of students struggle with this topic and just like with many topics, the problem lies within the foundational understanding. A student may be struggling with how voltage and current behave in series and parallel circuits but has not noticed that they do not understand what voltage and current is.

Once you understand these concepts properly, less energy is required to remember a series of isolated facts and equations as everything is integrated and so can be derived from first principles.

Taking this approach also has two other important benefits. You get the marks on the harder questions in which your understanding is really being put to the test and you actually feel like you are learning something and so are more engaged. This will form the first part of a little series of posts on the topic of electricity.

I will be focusing around 4 words within this post: Current, voltage and charge.

USING COMPUTER GAMES TO LEARN

What is Charge?

Charge can be negative or positive. It is measured in coulombs, which have the symbol C and the symbol for charge is Q. Some particles have charge, some do not. For example, protons have a charge of 1.6×10-19 coulombs and electrons have an equal and opposite charge (ie. -1.6×10-19 coulombs).

Opposite charged objects attract one another, (like opposite magnetic poles) and like-charged objects repel. Now, hopefully, you have realised that I haven’t really answered the question satisfactorily, right? That doesn’t exactly seem to explain what charge actually is. Well, firstly don’t worry… I don’t think many scientists really know what it is, and you certainly do not need to know at GCSE or A-level.

Why we should question

Secondly, when you think about it, the same can be said about many other things which we are more familiar with, but we are not in the habit of questioning. Why do things fall? Gravity. Why does gravity make things fall? Er… because they have mass, and a gravitational field causes masses to attract one another? Ok… Now that opens up a few more obvious questions: What is mass? Why do masses fall in a gravitational field? What causes things to have mass? Oh no! Now nothing makes sense! This is why to wary of anybody who claims to fully understand anything.

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And Current?

So now I have rest your mind at ease that nobody really knows what charge, I will talk about how this thing that we don’t really understand can flow around a circuit and be carried by certain charge carriers. A charge carrier is anything that has a charge and moves from one place to another. Pretty much all of the time, in a circuit, this is an electron.

If electrons are moving in roughly the same direction, current is flowing. Current (annoyingly) has the symbol I and is measured in amperes (amps for short) which, have the symbol A.

Electrons are free to move within a lump of metal which leads to certain characteristics specific to metals such as being good conductors of heat and electricity; being shiny; being able to bend without breaking and some other properties. Current is a measure of how much charge is flowing and how quickly. This can be worded in the following textbook style sentence:

Current is the rate of flow of charge.

So it is measured by how much charge is flowing past a point in a certain amount of time. This means, in theory, you could start a clock and count how much charge passes a point in whatever amount of time, in seconds, you choose and then divide the total charge by the time on the clock and you would have a measure of the current in amps.

Essentially, this is what an ammeter does. This is also why an ammeter is connected in series with whatever it is measuring the current of. The resistance of an ammeter is very low as it is designed to not affect the flow of electricity within the circuit and so things should be roughly the same whether the ammeter is wired in or not. Any good measuring device is attempting to peek inside somewhere without affecting what is going on.

So, current would increase if the electrons are flowing more quickly or if there are more electrons flowing.

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What About Voltage?

Voltage can be thought of as the amount of energy given to the charge. Of course, if charge has more energy you would expect it to flow more quickly right? That is exactly what happens. (More on this in the next post) So, voltage is the amount of energy per unit charge. Or we can think about it as the difference in energy per charge between two points. What type of energy are we talking about here? Well it is electrical potential energy as it happens. If two opposite charges are separated from each other, they have the potential to move closer together and as they do their electrical potential energy will be transferred into kinetic energy. All of this is why another word for voltage is potential difference and can be calculated in the following way:

I did want to talk about resistance in this electricity post, but I’m out of words! I will just leave the image below which sort of sums it up for now and I shall go into more detail in my next post.

Thanks for reading to the end and I hope you found it helpful!

A bit about the author, Paul H:

Paul is a qualified and experienced Physics, Maths, and Science teacher, now working as a full-time tutor, providing online tuition using a variety of hi-tech resources to provide engaging and interesting lessons.  He covers Physics, Chemistry, Biology, and Science from Prep and Key Stage 3 through to GCSE and IGCSE, plus teaches Physics, Maths, and Chemistry to A-Level across all the major Exam Boards.

You can enquire about tutoring with Paul here

The post What is Electricity? appeared first on The Tutor Team.

Keywords in Energy

This issue with terminology is particularly prevalent within this topic.

We use many of the words within these topics in everyday life a lot.

• ‘My phone ran out of power.’
• ‘I have no energy today.’
• ‘I had to force myself to do it.’

Some of these uses are spot on, some are in the right area, and some are way off.

So, let us make sure we understand some of these words more clearly so as we can understand our children when they are talking about them at school and, even better, so as we can correct our children when they are used incorrectly!

Energy

It comes in many forms, but in a nutshell, it is the ability to make something do something. In textbook speak, we say it is the ability to do work.

Work

Work is what happens when you apply a force to a system over a certain distance:

System

A system can be just thought of as whatever we are imagining or studying in a problem. For example, we might imagine how long it would take for my cup of coffee to cool down by a certain amount. I would measure the parameters of my mug, the coffee, and the temperature of the room it is in. All of this is the ‘system’.

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Transfers

Let us imagine we cycle to the top of the hill. Once we are at the top of the hill, we could roll down again. Now, what energy transfers are taking place?

We can see things are happening and so energy is being used or more accurately transferred. We are walking up the hill and then we’re rolling down it.

At the top of the hill, we can say we have more gravitational potential energy than at the bottom. In moving higher up, and further away from the centre of the planet, we have the potential to allow ourselves to move back down again and so we have this potential energy stored within us as such. As we allow ourselves to roll down the hill we start moving faster and faster. We are gaining kinetic energy whilst at the same time losing gravitational potential energy. This is an example of an energy transfer.

So where did the energy come from to get us up the hill in the first place?

Food, right? We ate some food and that gave us the energy to move up the hill. The food contained chemical energy which is a type of energy locked up in atoms and molecules which can be released using a chemical reaction. The chemical reaction which released this chemical energy is called respiration.

Once again, we can see a potential misconception. Respiration is not breathing! It is a chemical reaction that happens inside our cells in which the sugars from the food we have eaten are reacting with the oxygen we have breathed in and produce carbon dioxide and water vapour. Although the purpose of the reaction is to release energy which is used, amongst other things, to contract our muscles and allow us to move up the hill. The transfer here is chemical to kinetic energy.

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Conservation

And what about the food we ate? Where did that get the energy from? Well, if it was meat, the animal from which it came may have eaten meat and/or plants. Plants get their energy from the sun via photosynthesis. This comes up again in food chains and webs.

The main thing to take away from this is that energy is never created or destroyed. It is only transferred from one type to another. There has always been the same amount of energy in the universe, but where it is and in what form changes constantly.

Dissipation

Once you’ve rolled down the hill, you have less energy from ascending it and you do not have the gravitational energy because you’re at the bottom again and you’re not moving so you do not have kinetic energy either. So where is it now? We can say it has been dissipated throughout the surroundings. The atoms and molecules are jiggling a little bit faster than they were before, but it has been spread out so much the difference cannot be measured and is no longer useful.

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Conclusion

So, hopefully, you now have a better idea about what energy is and how it can be transferred from one form to another. If you feel you do not completely understand it that is quite normal. Many scientists still do not feel they completely understand it either!

But… that is what science is all about. Expecting you will never know everything about how things work, but to keep trying anyway!

A bit about the author, Paul H:

Paul is a qualified and experienced Physics, Maths, and Science teacher, now working as a full-time tutor, providing online tuition using a variety of hi-tech resources to provide engaging and interesting lessons.  He covers Physics, Chemistry, Biology, and Science from Prep and Key Stage 3 through to GCSE and IGCSE, plus teaches Physics, Maths, and Chemistry to A-Level across all the major Exam Boards.

You can enquire about tutoring with Paul here

The post Energy appeared first on The Tutor Team.