Fleming: Left or Right Hand?

Posted in A2 Unit 4: Magnetic Fields, AQA A2 Unit 4 by Mr A on 21 Feb 2010

Fleming, like most people, had two hands. Unlike most, he had a rule for each. But when should you use the left, and when the right?

 

LEFT HAND RIGHT HAND
A motion occurs due to the current. To work out what direction this motion is in, use the Left Hand Rule. A current is induced in the wire due to the applied motion. To find out in what direction this current flows, use the Right Hand Rule.

 

Moving a wire in a magnetic field

Posted in A2 Unit 4: Magnetic Fields, AQA A2 Unit 4 by Mr A on 21 Feb 2010
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Electric Fields Applet

Posted in A2 Unit 4: Electric Fields, AQA A2 Unit 4 by Mr A on 14 Feb 2010

Electric Fields

Posted in A2 Unit 4: Electric Fields, AQA A2 Unit 4 by Mr A on 23 Jan 2010
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Gravity Wells via xkcd.com

Posted in A2 Unit 4: Gravitational Fields, AQA A2 Unit 4 by Mr A on 11 Jan 2010

Capacitors in Series and Parallel

Posted in A2 Unit 4: Capacitors, AQA A2 Unit 4 by Mr A on 7 Dec 2009

The total effective capacitance of a group of capacitors in parallel can be found to be:

C_{total} = C_{1} + C_{2} + C_{3}

The total capacitance of a group of capacitors in series can be found to be:

\frac{1}{C_{total}} = \frac{1}{C_{1}} + \frac{1}{C_{2}} + \frac{1}{C_{3}}

Now try this worksheet on Capacitors in Series and in Parallel

Charging and Discharging Capacitors

Posted in A2 Unit 4: Capacitors, AQA A2 Unit 4 by Mr A on 22 Nov 2009
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Introduction to Capacitors

Posted in A2 Unit 4: Capacitors, AQA A2 Unit 4 by Mr A on 18 Nov 2009
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Brass Pendulum and Lenz’s Law

Posted in A2 Unit 4: Magnetic Fields, AQA A2 Unit 4 by Mr A on 12 Nov 2009

A potential difference is induced across the brass pendulum, and the current flows such that it opposes the motion of the pendulum (due to Lenz’s Law). Brass is not a magnetic material, so the magnet is not slowing down by attracting the brass (as shown by the fact that the pendulum with slits in is not slowed down). However, when the pendulum with slits in is swung through the magnetic field, the eddy currents (which cause the pendulum to slow) are not so free to move within it. Thus Lenz’s Law does not have as much effect; the current does not flow as much, so the motion is not opposed as much. This demonstrates Lenz’s Law, and why a laminated core is more efficient in a transformer.

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Transformers

Posted in A2 Unit 4: Magnetic Fields, AQA A2 Unit 4 by Mr A on 11 Nov 2009
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Extras

Try out a transformer demo applet

TED talk on Wireless Electricity: