You did the questions on P113, and then started the questions on P118.
If you are still not 100% sure about the lens formula then you may want to watch this video which shows some examples.
Homework
We are missing all our lessons next week :( Ideally it would be great to finish the syllabus, so we can focus on revision and past papers after Easter. Here's what you need to do for this HW and both next weeks' HWs:
You need to know the parts of the human eye and what they do. Use the diagram on P114 to make notes on this. This video is quite good despite the strange voices...
You need to know what the 'near point' and 'far point' are, and what the ray diagrams look like for a normal eye focussing on a near object and a far object. Use the two diagrams on P115 for this. Copy those diagrams EXACTLY and note that the lens is more curved when focussing on the nearby object.
You need to know what 'long sight' and 'short sight' are, and how they are corrected. You also need to be able to draw ray diagrams for this. P116 will help, as will this video I just made.
You need to be able to comapre the eye with a camera - P115 and this video are excellent.
Finally you need to know how to calculate lens power. This is really easy - see top of P117 and this video.
We ray diagrams for a converging lens with the object exaclty at f, and the object at a distance less than f.
We verified the results experimentally.
We made notes on diverging lenses, and the ruls for constructing ray diagrams.
Homework
Draw a ray diagram for a diverging lens if you did not manage it in the lesson. You can watch this video which does lots of examples, but you don't need to watch it all.
Make notes on the lens formula using this video. No need to make notes on magnification again. Make sure you have a clear diagram that labels u and v. We will apply this formula next lesson.
SORRY!!! After posting the video above you pointed out that it uses a different version of the lens formula. We use the version 1/u + 1/v = 1/f.
Converging lenses
Classwork
We went over the ray diagrams you did for your HW.
You did a practical with a converging lens to recreate the scenarios from the HW.
Very carefully draw the diagrams and make notes on the properties of the image for the first three situations he discusses - up to do between 2f and f.
P110 may be useful.
Bring your notes to next lesson.
Total internal reflection, critical angle
Classwork
We finished the 'Analysis' side of the sheet from last lesson and went through it.
We made notes on total internal reflection and critical angle.
I demonstrated pulling a glass rod into a thin, flexible glass fibre and sent light along it.
Homework
Watch and make notes on this video and do the calculations yourself.
You did a simple practical with a rectangular block to find the refractive index of the material it was made from.
You did a better practical using a semicircular block to find the refractive index more accurately.
Homework
Make sure you have plotted a graph with sin(i) on the y axis and sin(x) on the x axis. Calculate the gradient - this is the refractive index of the block.
Use P201, the sheet I gave out in the lesson, and this video to make notes on the AC generator.
Bring your notes to next lesson.
Cover Lesson
Classwork
If you didn't watch it in the lesson, watch this video. **NOTE** you do NOT need to know the formula he mentions for your GCSE.
Make notes on the generator effect for a straight wire using the yellow box on P200. The important thing is that a voltage is induced when the wire cuts across magnetic field lines. If the wire is not moving, or if it is moving parallel with the field lines, then no voltage will be induced.
You can find the direction of the induced current using Fleming's Right Hand Rule. Stick in the diagram and label it - the fingers are the same as the left hand rule, but this is for when you are generating a current in a wire. We will practise this next lesson.
Answer Q1 on P201.
Homework
You can also induce a voltage in a coil of wire.
Watch this video and this video which demonstrate this effect. Make notes on this, and bring your notes to next lesson.
DC Motor
Classwork
I gave you some feedback on the HW - most people did not write enough.
Most of you managed to build a working DC motor.
DC Electric Motor
Classwork
We went over the sheet you did for HW.
I demonstrated the operation of a DC motor. Hopefully you can build your own next lesson.
We looked at a labelled diagram of a DC motor and explained how the split ring commutator allows it to turn continuously.
You answered some past paper questions and we started to go through them.
Homework
Check your answers to the rest of the questions from the lesson using this markscheme.
Answer Q1 on P209 and hand in on Monday morning before registration.
Motor Effect
Classwork
You learned the "right hand grip rule".
I demonstrated the motor effect, and you made notes on that.
I showed you Fleming's Left Hand Rule & we did a bit of practice.
Homework
Watch this video about the motor effect - is a better demonstration than the one I did in class.
We finished going through both sides of the oscilloscope sheet.
I started to give you a multiple choice quiz about heat transfer.
Bulbs, diodes, oscilloscopes
Classwork
We went through the HW sheet on light bulb costs.
We made notes on diodes and half-wave rectification, and I demonatrated this with an AC power supply and some LEDs.
You started to go through the oscilloscope sheet I gave out before half-term, and we went through the first one together.
Homework
Finish off the oscilloscope sheet and bring to next lesson.
Recap questions, lighting
Classwork
You answered Q7-8 on P192 and we went through these.
I started to talk about incandescent light bulbs - more on this (and other types) next lesson.
Homework
Complete the lighting choices sheet and bring to tomorrow's lesson.
Electricity recap
Classwork
We went over:
cost of electricity
parts & voltages of the national grid
why transformers are used
fuses, circuit breakers and RCCBs
Well done for making excellent progress while I was away.
Questions
Classwork
Answer the questions on P193 and check your answers. It should take about 45 minutes to answer the questions, leaving 20 minutes to mark and correct them.
Homework
Go through what you have done and make a list of things you want to ask me when I get back.
Power & cost of electricity
Classwork
Read and make notes on P186-7.
Answer the questions on P187 and check your answers.
Recap on what we have covered so far, and re-watch any videos if necessary.
Electrical safety, national grid
Classwork
Answer the questions on P181 and check your answers.
Read and make notes on P190-191 (the national grid).
It doesn.t say a lot about transformers . basically at this stage you need to know that they are devices that change the voltage (and current) of AC electricity. A step-up transformer increases the voltage and decreases the current. A step-down transformer does the opposite.
Answer the questions on P191, and check your answers (they will be given to you).
You used an oscilloscope to look at the voltage across a lamp connected to an AC power supply.
You found the amplitude (should have been between 5 and 10V), the period (should have been 0.02s but I expect some variation there) and the frequency (should be 50Hz, but again I $
You wired a plug in pairs - some more successfully than others.
We made some notes on mains electricity - the voltage, frequency, and the difference between the live and neutral wires.
We started to look at fuses and fuse ratings & I demonstrated some fuse wire blowing. Here's a slow-mo video I made last year.
Homework
Answer the questions on P183 and hand in before registration on Monday morning.
AC & DC
Classwork
We went through the test.
We made some notes on AC and DC, and I demonstrated a few things with the slow motion camera and this simulator.
Homework
Make notes on Cables and Plugs using P178-9 and the first six minutes of this video.
Bring your notes to next lesson.
End of topic test
Classwork
We did the test.
Homework
No homework.
Revision
Classwork
We did a hard question that combined levers and hydraulics.
We put some people in the hot seat.
Homework
Revise for test next week.
NOTE THAT WE HAVE MOVED THE TEST TO TUESDAY!!!
Past paper questions
Classwork
We made notes on the three factors that affect the size of the centripetal force.
You continued with the past paper questions I gave out last lesson.
I gave out the markschemes so you can go through them.
Homework
Revise for the test next Thursday.
Past paper questions
Classwork
I demonstrated a hydraulic jack, and showed that it uses a combination of a lever and two hydraulic pistions to achieve the necessary multiplication of force.
We did an example of working out the output force from a hydraulic system, and noted that the ratio of the piston areas is equal to the ratio of the input and output forces.
Watch this video about force multipliers and make notes.
Circular Motion
Classwork
We plotted the graph from last lesson's practical, and discussed the reults with reference to the formula F=mv²/r (though you don't need to know the formula).
We predicted what would happen if you whirled an object round on a string then let go, and we tried it.
We did a practical to investigate the repationship between speed and centripetal force - we will plot a graph next lesson.
NOTE: I'm trialling a new whiteboard so you can see notes from the lesson. The link is here. We'll see how it goes.
Circular Motion
Classwork
We went through the HW in detail, using the actual GCSE markscheme.
We considered some objects (like cranes and cars) and how their stability can be improveed. We watched a few videos showing actual toppling tests for buses: first one, second one.
We started to make notes on circular motion, and got up to describing the centripetal acceleration and centripetal force.
I showed you this simulation where you can send stuff into orbit.
Homework
Answer the questions on P61 and hand in on Monday morning before registration.
this video will help - watch it up to 6:08 when he starts talking about the bucket of water.
We started to make notes on stability - next lesson we will see how objects can be more or less stable.
Even More Moments
Classwork
We went through the HW. Please make sure you have corrected your answer to the penultimate question (about the people on the see-saw) - if you still can't do it, ask me.
We did some harder moments problems where you really had to think about which direction the moments were acting.
We did an experiment to find the weight of a ruler by balancing it off centre. See Figure 3 on P57.
We made notes on how to identify the "perpendicular distance" - you will practise this for HW.
Homework
Complete both sides of this sheet and hand in before registration on Monday.