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changing state – latent heat of fusion/vaporisation

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Before the holidays, we performed a set of experiments to determine the latent heat of fusion and latent heat of vaporisation of water.  Next week, we’ll review that work and think about possible reasons why our results were not closer to the “book” values.

The attached pdf provides a summary of the topic.

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National 5 – Satellites

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We’ve started looking at telescopes and this BBC programme from 2 years ago featured the replacement for Hubble, the James Webb Space Telescope.  The presenter, Maggie Aderin Pocock now hosts The Sky at Night on BBC4.

Please take some time to watch both parts of the film.  Maggie covers the basic idea of satellites, how we achieve geostationary orbit, looks at examples of Earth observation and the manufacture of the James Webb’s massive 6.5m mirror.  In part 1, around 17 minutes in, you’ll see satellite footage over the Highlands, can’t quite see Thurso though.

Satellites-part1 from mr mackenzie on Vimeo.

Satellites-part2 from mr mackenzie on Vimeo.

If you want to download a copy of the video to watch later, use the download link below.  Please be patient, the file is about 660MB in size.

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capacitors

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You recently completed the topic on capacitors in dc circuits, finishing off with a detailed study of the graphs obtained for current & voltage against time when a capacitor is charged or discharged through a series resistor. There are some additional notes and practice questions at the end of this post but please watch the embedded video clips first.

This introduction to capacitors from the nice people at Make Magazine is a good starting point.

[vimeo http://www.vimeo.com/3386456 w=400&h=225]

The S-cool revision site has some helpful notes and illustrations on capacitor behaviour; try page 1 (how capacitors work) and page 2 (charging and discharging).

There is information on charging and discharging capacitors on BBC Bitesize.

 

Use your knowledge of capacitor behaviour to explain how a flashing neon bulb can be controlled using a capacitor & resistor arranged in series. Here is a short video introduction to help with that.

[vimeo 29198676 w=500 h=281]

Blinking Neon Bulb (5F30.60A) from Ricardo Alarcon on Vimeo.

There are people working to replace heavy battery packs with modern, high capacitance devices called supercapacitors. These supercapacitors have superior energy storage compared to the normal electrolytic capacitors you will have used in class. This video goes one step further and shows the fun you could have with an ultracapacitor. Do not try this at home!

[vimeo http://www.vimeo.com/27087359 w=400&h=225]

Of course, you can always make your own capacitor with paper and electrically conductive paint.

[vimeo http://www.vimeo.com/34079522 w=400&h=220]

Finally, you looked at capacitors in ac circuits. You need to know that a capacitor will allow an ac current to flow. The current in such a circuit will increase as the current increases. Mr Mallon’s site has a revision activity about capacitors in ac circuits.

Now download the pdf below. It contains notes to help with your prelim revision and some extra capacitor problems.

Thanks to Fife Science for the original pdf from Martin Cunningham.

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