# Y13 Physics

• ## Past Paper Questions on Fields

• ### Classwork

• I gave out these questions on fields, with the markscheme too.
• You worked through them and made good progress. There are some really good (and tough) questions there.
• Here is my solution to the ball dropped in a magnetic field. It ended up as two parametric equations in t.
• Let me know how you get on know that you know how to do the cross product.
• ## Key terms, fields

• ### Classwork

• We went over a load of key terms, and discussed some aspects of fields (potential, potential gradient) in detail.
• You started some past paper questions on gravitation - the answers are here.
• LV found some really useful notes. AS notes are here and A2 notes are here.
• ## Past Paper Questions

• ### Classwork

• I gave out some past paper questions on further mechanics and you worked through them.
• We discussed what might happen if you dropped a charged ball in a uniform vertical gravitational field with a uniform horizontal magnetic field. Let me know if you work out the answer.
• ## Logs, verniers & micrometers

• ### Classwork

• You did a task to find some info from a log log graph.
• We made a simple Vernier caliper and used it to recap on how Vernier scales work.
• We then made some measurements using a ruler, a real Vernier caliper, and a micrometer.
• You did some more of the sheets that I gave out last week.
• ### Homework

• Continue your revision for the EMPA.
• ## More EMPA Revision

• ### Classwork

• I gave you a strange graph task. I guess the idea with this type of question is that in the formula, measured quantities (in this case S and T) can appear in more than two sererate terms.
• You job is then to make the measured quantites only appear in two separate terms, so they can be plotted on the x and the y axis. They can appear in any form you like (e.g. 1/T or S/T or whatever) as long as the resulting graph is linear.
• You then did a past A2 task, and I gave you the Part B and the markscheme to go over at home.
• ### Homework

• Do the Part B paper, and then mark using the markscheme. We can discuss any issues on Tuesday.
• ## Mock EMPA Feedback

• ### Classwork

• I gave you some feedback on the paper you did.
• We went over absolute and percentage uncertainty, and did some examples.
• We briefly discussed the funny graph question from that paper - I will try to come up with another example like that for you to have a go at.
• I gave out a couple of resources that Mr H made that should be useful for you: this is a whole EMPA with the data already collected (you can find the markscheme online), and this has some part B questions with the markschemes provided.
• ### Homework

• Continue your revision for the EMPA.
• ## EMPA Past Paper

• ### Classwork

• You did the last part of this paper. We will go through it on Tuesday.
• ## EMPA Past Paper

• ### Classwork

• You continued with the past EMPA paper.
• NOTE: we will do the final part next lesson on Friday. The paper is 1 hour 15 mins long, so if you want the full time, please arrive 5 minutes early.

• No HW.
• ## EMPA Past Paper

• ### Classwork

• You did a past EMPA paper - we will continue with this after the holidays.
• I gave back your mock papers. On the whole these were very good, but a few of you will want to improve.
• One of the biggest areas seems to be the multiple choice questions, and managing time effectively. If this was an issue then make sure you do lots of multiple choice questions.
• ### Homework

• If you are revising over Easter then obviously past papers are a good choice. However, there are only 9 available for unit 4, so don't do them all. You want to save some for later revision.
• If you do a past paper, then make sure you do the whole thing under timed conditions, and keep an eye on how long you spend on each paper. You can convert your mark to a grade here.
• If you don't want to use up all the Unit 4 past papers, there are lots of past paper questions here and answers here. I would recommend using these, and spreading the real past papers out between now and your exam.
• I will also try to make some videos of how to approach the multiple choice paper.
• Have a good Easter!
• ## Mock

• ### Classwork

• You did the mock.
• I will mark it and put it in your pigeon hole as soon as I can.
• Next lesson we will begin our EMPA practice by doing a practical, so you don't really need to do any preparation for that.

• No homework.
• ## Eddy currents, back emf

• ### Classwork

• You did a quick question about dropping a magnet through a coil, which we went through.
• We agreed on mock timings - please arrive in time to start either at 8:20 to finish at 10:05 or at 9:55 to finish at 10:40.
• I demonstrated eddy current braking in a spinning metal disk, and we discussed eddy currents in transformer cores. More here.
• I started explaining back emf but we ran out of time. It's not that hard - see HW video.
• ### Homework

• If you like you can watch this video which I just made about back emf.
• Revise for mock on Friday.
• ## More EM Induction

• ### Classwork

• You did some EM induction questions.
• We made notes on the magnetic field due to a current carrying wire, the right hand grip rule to find the direction of the field, and the force between two parallel wires. I demonstrated this, and we considered AC and DC currents.
• We then looked at Lenz's law, and how to find the polarity of an electromagnet using another right hand grip rule. You can use this model to verify.
• ### Homework

• Add to your notes on generators using P128. You don't need to add much - mostly that the peak emf is given by BANω.
• Play with this model with and without the commutator to ensure you are happy with how AC and DC generators work, and the effect of varying the frequency with which the coil is rotated.
• Answer Q1-2 on P129 and hand in on Monday morning.
• ## Induced emf in coil

• ### Classwork

• You induced an emf in a coil using a practical setup like this.
• We derived the formula ε = Blv by using the concept of rate of flux cutting.
• We looked at when an emf is and is not induced in a coil, and we tried lots of different ways of inducing an emf in a coil (including constructing a model bike dynamo and also a transformer).
• You answered Q1-2 on P126.
• ### Homework

• In class we mentioned rotating a coil in a magnetic field, but didn't do any calculations.
• Read and make notes on the AC generator on P127, including the graphs.
• This video is good, but is a bit heavy on the maths, and may confuse you if you don't know about vector dot products.
• This video is a bit annoying, but is generally good. Except what she calls the 'armature' I would call the 'coil'. The armature is a separate part.
• In the lesson I demonstrated this phenomenon. Find out why it takes the magnet so much longer to fall than the iron.
• Bring your notes and explanations to next lesson.
• ## Induced emf in a wire

• ### Classwork

• You did these questions on mass spectrometers.
• I demonstrated a Hall probe. The result it gave for the big magnet was similar to what we calculated using F = BIl, but didn't agree amazingly.
• KG demonstrated an emf being induced in a wire moving in a magnetic field.
• We made some brief notes, including the formula ε = Blv.
• ### Homework

• Watch this video and this video to recap on inducing a voltage in a coil (which you did at GCSE).
• No need to watch the whole length of each video, or make notes unless you've forgotten it all. We'll go over it next lesson anyway.
• Watch and make notes on this video. Make sure you are clear on what flux density, flux, and flux linkage are, and the units for each.
• Next lesson we will use ideas about 'flux linkage' to analyse the induction of a voltage in a coil.
• ## Presentations, questions

• ### Classwork

• You did your presentations on cyclotrons, synchrotrons, and mass spectrometers.
• We made notes on the 'velocity selector' component of the mass spectrometer.
• You started the questions on P115.
• ### Homework

• Finish the questions on Q1-2 P115 and check your answers in the back of the book.
• Make notes on Hall Effect using P111-2 and this video.
• Bring to next lesson.
• ## Moving charges in fields

• ### Classwork

• We looked at charged particles moving in electric fields and magnetic fields.
• We did some calculations for a beam of electrons being accelerated by a voltage and then deflected by an electric field. They worked out really well.
• Then we looked at the effect of magnetic fields on charged particles, and derived an expression for the radius of the circular path of a particle.
• We will do some questions on this after half term.
• ### Homework

• Prepare a short presentation in groups of two or three on either cyclotrons or synchrotrons or mass spectrometers.
• The focus of your presentation should be on the role of electric and magnetic fields in these devices.
• Hopefully you can present on Tuesday after half term.
• ## Test feedback

• ### Classwork

• We went through the test in detail as there were some tricky parts.
• I showed you an electron gun that fires a beam of electrons at a screen, and we deflected the beam with an electric field.
• ## Test

• ### Classwork

• You did a test on fields and capacitors.
• ### Homework

• Have a go at this game that I made a few years ago.
• Dots show magnetic field coming out of the screen; crosses show field going into the screen.
• What happens when the charged particle passes through electric and magnetic fields? How do they change the partice's speed and direction? What shape is the particle's path through each field?
• ## Electric Motors

• ### Classwork

• We looked at the variation of the torque on a coil on the angle of the coil.
• We discussed how real motors reduce the variation of torque as the motor rotates, and watched this video which was really good. We stopped watching when he got to shunt/series motors - I imagine this will make more sense when we have learned about 'back emf'.
• I gave you a labelled diagram of a DC motor and showed you a demonstration motor.
• You did the questions on P109.
• We discussed latitude, longitude, the longitude problem, compasses, etc. There is lots of intresting stuff to read about if you google it.
• ### Homework

• Revise for test on Friday.
• ## Introducing Magnetic Fields

• ### Classwork

• We did an investigation together to investigae the force on a current carrying wire in a magnetic field.
• We observed that the force was in the direction predicted by Fleming's left hand rule, and found the effect of current, length, and angle on the force.
• We looked at the formula F = BIl and then applied it to a coil of wire.
• We developed numerous expressions for the torque on a coil of wire in a magnetic field, culminating with T = BIAn.
• Next week we will look at the effect of the angle of the coil on the torque.
• ### Homework

• Revise for test next Friday.
• ## Past Paper Questions

• ### Classwork

• You did a question about a capacitor discharging to another capacitor.
• You used a student-friendly markscheme to mark each other's past paper questions.
• You finished off the rest of the past paper questions in the book (Q6-8).
• ### Homework

• Use the markscheme I gave out to mark Q6-8.
• Revise for test next week on fields and capacitors.
• ## Datalogging

• ### Classwork

• We went over the graphs I set for HW.
• We showed why exactly half the energy is lost when charging a capacitor.
• You collected data for the time constant of capacitor discharge with different resistances using a datalogging system.
• We agreed to to a test on fields and capacitors on Friday 5th Feb.
• ### Homework

• Answer Q2-5 on P102-104.
• Bring to next lesson.
• ## Capacitor Discharge Calculations

• ### Classwork

• We briefly looked at the formulae for capacitor discharge through a fixed resistor, and how they are derived.
• You answered Q1-3 on P101.
• We looked at an application of capacitor discharge for timing a collision. More on this next lesson (we can compare with video analysis).
• We observed a capacitor discharging through a voltmeter alone, and compared the resistance of an ideal voltmeter (infinite) with a digital multimeter (1MΩ) and an analogue voltmeter (~5kΩ).
• ### Homework

• Read and make notes on "Charging a capacitor through a fixed resistor" on P100-101, and answer Q4 on P101 if you haven't already.
• On another sheet of paper, copy figure 4a from P101, and sketch graphs to show how these things vary with time after the switch is closed:
• a) voltage across the capacitor
• b) voltage across the resistor
• c) voltage across the cell
• d) charge on the capacitor
• e) current through the capacitor
• f) current through the resistor
• g) rate of energy transfer by the battery (i.e. power)
• h) rate of energy dissipation by the resistor
• i) rate of change of energy stored on capacitor
• Sketch these and hand them in tomorrow morning. If you can work out the formula for each of these functions that's great - if not just sketch what you think it will be.
• ## Capacitor Discharge

• ### Classwork

• You created an iterative model for the discharge of a capacitor through a fixed reisitor.
• We discussed one drawback of the model, and how it could be improved (i.e. by decresing the time between each iteration and using a computer to save effort).
• You plotted graphs of charge, current and voltage against time for your model, and verified that they showed exponential decay.
• You then did a practical to gather voltage and current data over time for the discharge of a real capacitor.
• We discussed the potential benefits of using a datalogger to collect data - we will do this next week.
• ### Homework

• Read and make notes on P98-99.
• Note that there are two ways to find the time constant. If you know R and C, the time constant is RC. If you have a graph of voltage/current/charge against time, then the time constant is the time it takes for the voltage/charge/current to fall to 0.37 of its initial value.
• For the real data we collected in the lesson, calculate the time constant using both of these methods.
• ## Capacitor charging at constant current

• ### Classwork

• You did a practical where you charged a capacitor at constant current and determined the capacitance.
• Unfortunately I connected the capacitors the wrong way round for you (oops...) so the results were somewhat non-linear, but they were still pretty good.
• We then started to look at the energy stored on a capacitor, and I compared the situation to the energy stored in a spring.
• ### Homework

• Read P96-7 and add to your notes on energy stored.
• Answer the questions on P97 and hand in tomorrow morning before registration.
• ## Capacitors

• ### Classwork

• We started off by looking at the idea of surface charge density, and the relation between surface charge density and surface electric field strength.
• Then we started looking at capacitors - what they are, what they do, and what they are used for.
• I demonstrated a few capacitors - some awful (that I made from bits of stuff around the lab) and then an amazing 1 farad capacitor.
• We started to look at the formula for the voltage across a capacitor - more on this next lesson.
• ### Homework

• Read P94-5 and add to your notes - there are quite a few extra bits on these pages.
• Answer the questions on P95 and hand in before registration on Monday morning.
• ## Fields recap

• ### Classwork

• I went over some stuff you have covered on your own about radial and uniform electric fields.
• We did a tricky problem about a charged particle falling through an electric field.
• ### Homework

• Answer Q1-3 on P90-91 and either hand in on Monday or bring to the lesson on Tuesday.
• If I don't see you on Tuesday, have a good holiday!
• ## COVER LESSON

• ### Classwork

• Read and make notes on P76-8. There is QUITE A LOT on these pages.
• The first half of this video may help.
• ### Homework

• Answer the questions on P79 and hand in before registration on Weds morning.
• ## Electric charge

• ### Classwork

• We discussed similarities and differences between electric and gravitational fields.
• I demonstrated the interaction between charged and neutral spheres, both isolated from and connected to earth.
• We did a few more demonstrations using the Van der Graff generator.
• You started to answer the questions on P75.
• ### Homework

• Read P83-85 and answer the questions on P85.
• Hand in before registration on Monday.
• ## Finishing Gravity

• ### Classwork

• We did some past paper questions about gravity and went through the answers.
• We made notes on adding potentials due to different objects (add as scalars) and what potential gradient represents.
• ### Homework

• Watch and make notes on this video about electricity.
• ## Satellite Orbits

• ### Classwork

• We worked out the radius of the orbit of a geostationary satellite.
• We worked out the difference in gravitational potential between the Earth's surface and this distance, and hence calculated the change in GPE for a 500kg satellite put into this orbit.
• We calculated the kinetic energy of the satellite (on the equator) and also in its orbit, and worked out how much extra kinetic energy it needed to be put in this orbit.
• ### Homework

• Celebrate 100 years of general relativity by watching this video and if you want to also this video
• They are not posh videos with easy to understand simplifications, but they actually get across some very interesting ideas.
• ## Gravitational Potential

• ### Classwork

• We showed why the gravitational field inside a spherical shell is zero, and used this to work out the variation of g with r inside a solid sphere.
• We started to look at gravitational potential energy, and came up with the idea of gravitational potential.
• We explored gravitational potential and equipotential surfaces for uniform and radial fields.
• We derived the formula for the potential at a certain distance from a point mass or sphere.
• ### Homework

• Answer the questions on P58 and hand in tomorrow morning before registration.
• Here are some curve sketching problems for those of you who are interested.
• ## Gravitational field strength

• ### Classwork

• You worked out the point between the earth and the moon where their gravitation fields cancel out.
• We discussed what would happen to an object placed at this point, and I mentioned Lagrange points (google them to find out more).
• We defined gravitational field strength, and found the formula for the field strength due to a point mass (or sphere).
• ### Homework

• Make notes on P62-3 on the field stregnth of a planet and its variation with distance from the centre of the planet.
• Leave out the bit about potential.
• Here is a video about inverse square relationships that may be useful.
• ## Gravitation

• ### Classwork

• We went through your test from last half term.
• We started to look at gravity, and looked at:
• uniform and radial field shapes
• Newton's law of universal gravitation
• the reason you can treat spheres as points
• ### Homework

• Answer the questions on P61 and hand in tomorrow morning.
• ## Test

• ### Classwork

• You did the test.

• No homework.
• ## Lots of questions

• ### Classwork

• You did these multiple choice questions.
• You did these hard momentum questions.
• We discussed the problem from the video last week about the sand falling onto the balance.
• I demonstrated two coupled pendulums. (Also if you read the first comment you will see that this situation invovles beats too!)
• ### Homework

• Revise for test on Friday.
• ## Momentum past paper questions

• ### Classwork

• You worked through these past paper questions from Jan 2010.
• We discussed whether flying birds in a van would break a weak bridge, then I demonstrated it with a helicopter hovering over a balance.
• ### Homework

• Do some revision in preparation for a test next Friday.
• ## Independent Work

• ### Classwork

• Collect your answers to P46 from my locker (hopefully they will be there if you haneded them in on time) and make any necessary corrections.
• Answer Q3-7 on P51-53 and bring your answers to Friday's lesson.
• ### Homework

• We've covered all the basic theory from these chapters, but there are a few more tricky applications of things you should know about.
• Watch this video and see what answers you can come up with before next lesson.
• If you still have time, do some revision in preparation for a test on Chapters 1-3 on Friday 16th.
• ## Driving, damping, resonance

• ### Classwork

• We went over the concepts of damped oscillations, driven oscillations and free oscillations.
• I did a few demonstrations of various things, including resonance of an air column in a measuring cylinder (similar method to this), beating of two notes on a guitar, and damping a mass-spring system with water.
• We started to look at a hard momentum question about a helicopter hovering.
• ### Homework

• Try this beats experiment on your computer. It's pretty amazing!
• Answer the questions on P46 and hand in tomorrow morning if possible - then I can give it back to you on Thursday.
• If you're an engineer (or like cars) then maybe watch this video about car suspension.
• ## SHM Energy Graphs, resonance

• ### Classwork

• We went through the graphs for:
• potential energy and kinetic energy vs time
• potential energy and kinetic energy vs displacement
• force vs displacement
• We did three resonance experiments - we will go through the results from these next lesson.
• ### Homework

• Read P44-46 and make notes on energy and damping (we already considered the energy vs displacement today in graphical form).
• Watch this video which gives an amazing demonstration of damping.
• You can watch this too if you like but it's not essential - does give some interesting extra maths that you don't really need to know.
• ## More Circular Motion

• ### Classwork

• We recapped on the SHM ideas we have covered so far.
• You worked through these past paper questions - the very last part about energy we have not done yet, and will learn more about it next lesson.
• ### Homework

• You have done a lot in the last week, so take some time to go over what we have covered so far.
• You could also spend some on the Physics Challenge paper, or work on your UCAS or Cambridge forms.
• ## Independent Work

• ### Classwork

• By this stage you should know that for SHM:
• displacement = Acos(2πft)
• acceleration = -(2πf)²x;
• maximum displacement = A
• maximum velocity = (2πf)A
• maximum acceleration = (2πf)²A
• Today I want you to work on P40-43 to find out about mass-spring systems and pendulums.
• I will post a few videos soon that will help show you how the formulae are derived, although you don't need to be able to derive them - just apply them.
• Make notes on the videos and P40-43, then answer all the questions on P43 and check your answers in the back of the book. Bring these to next lesson.
• ### Homework

• Watch this video which is a bit boring in places, but has some good demonstrations about resonance.
• Watch this video which introduces the concept of 'natural frequency'.
• No need to make notes on these - just make sure you have watched them before our lesson on Friday.
• ## Investigating a mass-spring system

• ### Classwork

• We looked at a few examples of oscillatory motion and tried to work out whether they were SHM or not.
• We did a pracitcal to find the relationship between mass and period for a vertical mass-spring oscillator.
• ### Homework

• Complete your graph, and work out your values for A and B.
• Have a look at P41 which shows the formula for a mass-spring system - your value for B should be close to ½, and your value for A should be close to 2π / k½ (you will have to work this out for your k).
• Watch this video, then answer the questions on P39.
• You might also want to look at this video and this video which show working through some examples of SHM questions.
• ## Simple Harmonic Motion

• ### Classwork

• We watched a video of circular motion and plotted the y component of its motion over time - the y displacement, then the y velocity, then the y acceleration.
• I then demonstrated that a pendulum swinging from side to side looks a lot like one component of circular motion, by swinging a pendulum above a turntable (see P38 of the textbook).
• The motion of the pendulum is called 'simple harmonic motion' - we then thought of other oscillating motions that were or were not SHM.
• After rec I demonstrated a trolley between two springs (see P40), and we saw that in this case the acceleration was proportional to the displacement, and in the opposite direction. This defines SHM.
• I then baffled some of you with some differential equations, which you can largely forget. The main thing is the conclusion that
x = Acos(2πft)
• ### Homework

• Watch the first three minutes of this video about SHM. You can wathc the rest if you like - it will be useful later in the topic.
• Watch this video from 2:08 to 3:47 and make sure you are happy with the graphs of motion that are found on P36 of the textbook. Again, you can watch the rest of the video if you like, but that bit is enough for now.
• By next lesson you should be happy with the definition of SHM, and be clear about the shapes of the graphs on P36. We will go over the formulae we did today next lesson, so don't worry too much about those.
• ## More Circular Motion

• ### Classwork

• We considered the centripetal force on three children at different positions of a merry-go-round.
• This led to a reformulation of the formulae for centripetal acceleration and force in terms of ω.
• We went through the last question of the HW, and then calculated the maximum speed for the car not to leave the ground in P27 Q1.
• We did a practical to investigate the relationship between speed and centripetal force.
• ### Homework

• One person in each pair: calculate v² for each row, then plot a graph with v² on the x-axis and F on the y-axis. Find the gradient and the y-intercept.
• The other person in each pair: calculate log(F) and log(v) for each row, then plot a graph with log(v) on the x-axis and log(F) on the y-axis. Find the gradient and the y-intercept.
• Watch Part 1 and Part 2 of this video about log-log graphs - hopefully it will help you make sense of what is going on.
• We will then go over what you have found next lesson.
• ## Circular Motion in Context

• ### Classwork

• We went through Q3 of the HW.
• We did some calculations based on the 'long swing' (see P28) for a weight attached to a strip of paper.
• We calculated the angle of bank of a velodrome bend that would require no friction at a certain speed.
• We did Q4 on P27.
• ### Homework

• Complete these circular motion past paper questions and hand in tomorrow morning before registration.
• Use P26 to make notes on a car going over a hill, and answer Q1 on P27. Bring these notes and Q1 to next lesson.
• ## Circular Motion

• ### Classwork

• We worked out the period, frequency, angular velocity and speed of a person standing at different points on the earth.
• We derived the formula for centripetal acceleration, and then centripetal force.
• We analysed the motion of an object on a string being swing around in a horizontal circle.
• We started to look at more examples of circular motion to identify what was providing the centripetal force.
• ### Homework

• Answer the questions on P29 and hand in before registration on Monday.
• ## Rockets, alpha decay

• ### Classwork

• We did these questions about rockets.
• We did Q5 on P21 about alpha decay.
• We started to make notes about circular motion.
• ### Homework

• Finish the notes by writing about ω (see P23).
• Answer the questions on P23 and hand in tomorrow morning before registration.
• Optionally watch this video - it's short and has some interesting demos.
• ## More Momentum

• ### Classwork

• We calculated the total KE before and after the collisions from the first two questions from the HW.
• We did approximate demonstrations with trolleys of three of the four HW problems.
• We made notes on elastic and inelastic collisions.
• You did some problems that involved momentum and also springs from Y12 - well done for doing that without any help.
• Finally we looked at the situation where an object ejects mass at a constant velocity (e.g. a rocket) and we estimated with reasonable success the thrust of a space rocket.
• ### Homework

• Answer Q2-5 on P20-21 and hand in on Monday morning before registration.
• Optional: find out what the force vs time graph for the buffer looks like. You can work this out without solving a differential equation...
• ## Impulse, Bouncing Balls

• ### Classwork

• We did a quiz on impulse.
• You did a practical and calculated the average force of a table on a bouncing ball. This was very tough!
• ### Homework

• This HW is on collisions and explosions which you have done at GCSE.
• Answer Q1-2 on P13 and Q1-2 on P17.
• Here is a slightly boring collision example in case you've totally forgotten.
• Hand in on Wednesday morning before rec.
• ## Momentum

• ### Classwork

• We did a quiz on momentum.
• We started Q1-3 on P7.
• ### Homework

• Make notes on impulse and force-time graphs.
• Use P6-9 of your textbook and this video.
• This video has some examples of force-time graphs for different impacts.