Capacitor revision

We’ve just 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 clips first.

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

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.

Here is a video that covers some of the areas we discussed in class. Ignore the maths at the end of each section of the film, you won’t need it.  Notice how the man in the film uses a lightbulb, rather than an ammeter, to show when the current is large or small.  Clever, eh?

You must be explain how a flashing neon bulb can be controlled using a capacitor & resistor arranged in series.  We shall cover this in class but here is a short video introduction.

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

A few lessons back, I compared energy storage using normal electrolytic capacitors to a 10F supercapacitor, and we observed its superior performance in terms of energy storage.  This video goes one step further and shows the fun you could have with an ultracapacitorDo not try this at home!

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

We also 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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