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By mrmackenzie, January 30, 2012 8:33 pm

Here is your homework on the resistance topic.  Download the pdf with your questions by clicking on the download link below.

Please hand in your jotter no later than Tuesday 7th February.

Pupils going on the school ski trip should try hand their jotter in by the end of this week.

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By mrmackenzie, January 29, 2012 11:52 am

Here is a short test to let you find out how much you’ve learned about parallel circuits so far.  Click on the circuit diagram below to open the question page.  You will be asked to enter values for V1, V2, A4 & A5.

image courtesy of MATTER project

If you need some help to find all four values, click on the check answers button to view the working.

Are you ready for some more challenging questions on series and parallel circuits?  Try this page.

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By mrmackenzie, December 13, 2011 9:52 pm

We have been looking at electrical power this week.  The man I mentioned in class today is James Watt.  Here is a short biography by the BBC.  I also spoke about how he calculated the power output of working horses and compared them to his steam machines.  You can read more about his horsepower experiments here.
I’d say he’s a pretty famous scientist – not many people get their name on every lightbulb in the world! 

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By mrmackenzie, June 2, 2011 8:25 pm

What would you do with a great big electromagnet?  These people made a film.

F5 2011 RE:PLAY Film Festival. Inductance from Physalia Studio on Vimeo.

What do you make of the film?

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By mrmackenzie, March 26, 2011 1:13 pm

image by explainthatstuff

We’re finishing off the electricity unit by looking at electric motors.  The page I used in class to help explain how a simple electric motor works is available here.

Here is another nice animation that shows the key parts of an electric motor.  It will stop after a few rotations but just reload the page to see it again.

Real electric motors have a few modifications;

• they use field coils instead of a bar magnet – the field coils form a strong electromagnet when current passes through them.  The field coils do not rotate.
• the single rotating coil is replaced by several rotating coils
• there are more contacts on the commutator – each pair connects to a different rotating coil
• the brushes are often made from carbon instead of metal – the carbon conducts electricity and can withstand high temperatures.  Carbon also moulds to the shape of the commutator to give a good electrical contact

image by marrrci

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By mrmackenzie, March 7, 2011 7:59 pm

Wikipedia has a good description of how a ring circuit is used in home wiring.  The diagram below is neater than the one I drew on my board in class.  You can click on it to view a larger version of the drawing.

drawing by Andrew C.

• The ring circuit for power sockets is rated at 30A.
• The ring design allows electricity to reach the socket from two different directions, so the current flowing in any one wire is lower.
• Since the current is lower, a thinner cable can be used.  This saves money as copper is expensive.

Click below to download the Scout guide to home wiring.

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By mrmackenzie, December 20, 2010 7:37 pm

I have uploaded a set of notes on the Using Electricity unit.  Please click on the download link below and save a copy on your computer at home.  I would like everyone to read up to the end of page 19.  This will cover everything that we have looked at so far on this topic.

Please try to answer as many of the questions in these notes as you can, either by printing out the pages and writing in the spaces or using your Physics jotter.

You may leave a comment if you get stuck with anything and I will try to help.

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By mrmackenzie, December 6, 2010 8:19 am

If you can’t get to school due to the snow, here is some physics work so that you can keep up with the course.

We started looking at Ohm’s Law last week. Go to the HelpMyPhysics site and try the Ohm’s Law activities there.  I have also uploaded some additional problems taken from our classroom booklets. Click on the download link below to get your copy.  You can leave a comment here if you get stuck or want to ask a question.

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By mrmackenzie, January 11, 2010 5:03 pm

Due to problems with school transport, I have moved the tests scheduled for today and tomorrow.  The general test will now be tomorrow (Tuesday 12th Jan) period 1, with the credit test on Thursday14th Jan (period 6).

The calendar on the right has been updated to show these changes.

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By mrmackenzie, October 1, 2009 8:56 pm

Someone pointed out this cartoon and it reminded me of today’s lesson.  Get more cartoons at xkcd.com.