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Module P5 ­ Electric Circuits

Static electricity:

Build up of static electricity is cause by friction.
When you rub two insulating materials electrons move from one to the other, so one is
positive and one is negative (electrons are negative).
Electrically charged objects attract small objects.

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The standard circuit has an ammeter, a voltmeter in parallel with a component, and a
variable resistor. Oh, and a battery. Obv.
Voltmeters measure the potential difference between two points. So you have one
around the battery and one around the component so you can see how much energy

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UK mains are about 230v.
The current is constantly changing direction (alternating current).
Battery supply is DC (direct current).
AC is used for mains as it's easy to generate and is distributed more evenly.
Moving a magnet in a coil of wire induces current.
This is called electric induction.

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So, if something needs more power, it takes more energy, so a light might only take 100W
(that's 100J every second) but a kettle might take 2.5kW (2500J per second).
Energy transferred (J) = Power (W) x Time (s)
Kilowatt-hours (kWh) are UNITS of energy.
Energy is usually measured in…

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When a wave hits a material all waves can be reflected, refracted (through material but
change direction) and diffracted (bends round making it spread out).
o Angle of incidence = Angle of reflection
o When a wave hits a boundary between one medium and another, some is always

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There are seven types of electromagnetic waves.
o Ronald McDonald Is Very Ugly X-men Glow
o Radio ­ Micro ­ Infra red ­ Visible Light ­ UV ­ X rays ­ Gamma rays
o As you go the frequency increases (so does energy)
o And as you go the wavelength…

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FM waves have varying frequency.
o When there's a trough in the signal, the frequency is increased, or on a peak it is
increased. Or vice versa.
Receivers recover the original signal.
o They ignore the carrier part of the wave and extract the original signal. ^^^^^

Analogue and Digital…


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