Most of these should look familiar to you although relays & reed switches might be new. We will discuss them on another occasion. Make sure you can draw all of these symbols from memory. You are unlikely to need to draw a reed relay but you do need to be able to recognise one, and …
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Series:Electronics
Diode…
Diodes are electronic components that only allow the current to pass in one direction. They are used for smoothing out alternating current and filtering out the audio from radio transmissions. Laser diodes and LEDs emit light.
AC/DC…
Given my fondness for the band of the same name, it is strange that I have not used this title for a post before. AC/DC refers in this case to alternating and direct current. Mains electricity in the UK is 240 volt alternating current that switches polarity (flows the opposite way) 50 times a second …
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Resistance Is Useless…
Sometimes exam questions about circuits will use resistors instead of lamps. Lamps are just like resistors except that they glow white-hot whereas resistors do their resisting more discreetly. Solving problems with resistors instead of lamps uses all the same principles. Often they include ammeters to show the current flowing in a particular part of the circuit and ask …
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Ohm’s Law…
Understanding electric circuits is all about understanding the relationship between voltage, resistance and current. The voltage is the amount of electrical push in the circuit. This is usually controlled by the number of cells. Each cell is 1.5 volt so four cells connected in series are called a 6 volt battery. The picture to the left offers …
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But That Is Illogical Captain…
Mr Spock is the highly logical Science Officer supporting the impulsive Captain Kirk at the helm of the star ship Enterprise in the long running TV and film franchise – Star Trek. I seem to remember him often saying, “But that is illogical, Captain” although I cannot find a single example. Logic plays an important …
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Electromagnets…
An electromagnet is a magnet which is activated by the flow of electricity. This magnetism is temporary and can be switched off by removing the current. In fact, any wire with an electric current passing through it has a magnetic field surrounding it. This field is intensified by wrapping the coils around an iron core. …
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Transformers: Inductively Coupled Conductors In Disguise…
Oliver H asked me in class where the energy goes when mains electricity is stepped up or down inside a transformer. He correctly cited the first law of thermodynamics (or the law of conservation of energy) pointing out that when 240 volts from the mains is stepped down to 9 volts to run an electronic balance in …
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