Using Electricity

booklets for all standard grade physics units

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I’ve been asked to post a link to all of the booklets so that people have access to something like the energy booklet as they revise using electricity and electronics.  I’ve added these to the standard grade page now.  Look for a link called whole unit notes in each section.

For those of you who have yet to download a copy of the SQA Physics booklet, get yours here.

electric motors

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 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

S3 the kilowatt-hour

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Recently we looked at the way power companies calculate how much electrical energy we use in our homes.  The Joule is too small a unit to measure household energy consumption, so suppliers work out our bills using a must larger unit called the kilowatt-hour (kWh).

I found this page on BBC Bitesize that has some information and a quiz to test your kWh knowledge.  There is also a section on the kilowatt-hour at gcse.com.

parallel circuits

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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.

Power!

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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!  😉