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Glossary of terms you will come across during your Phase 2 training.



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In the context of LEDs, each of them has a value called 'forward voltage'.
This is the voltage that must be put on the anode of the diode in order for current to begin to flow through the diode.
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Represented in datasheets with the abbreviation Iq, quiescent current is the current used by a device when it is ready to operate, but not yet supplying any current to a load.

You can think of quiescent current as the current required have a device ready to perform a task, but not yet performing that task.

You could also think of it as the current used by a component when it is powered up, but not yet operating.

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Acceleration is simply a change in speed.

Acceleration can be positive - an object speeds up, or it can be negative - an object slows down.

The kind of acceleration we all experience every day is the acceleration produced by gravity - 9.81m/s2, referred to as 'g' in engineering calculations.

For example, in order to calculate the weight of an object, we multiply its mass by the acceleration produced by gravity:

W=m.g

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Gustav Kirchoff, image from WikipediaGustav Kirchoff, a German physicist, responsible for two electrical laws:

  • Kirchhoff's current law
    Current going into a circuit is always equal to the current coming out of a circuit - in other words, any electricity that goes into a circuit, must come back out of that circuit. 
  • Kirchhoff's voltage law
    In an electrical circuit, the total sum of the individual voltage drops is always equal to the supply voltage.
    For example, if you have a voltage of, say, 12V on a circuit with a single electrical load, and you measure the voltage drop across the load at 11V, this means that you are dropping 1V elsewhere in the circuit and you have a problem.
    Voltage drop in a circuit is unavoidable, so we have acceptable limits.
    For the live part of a circuit, the limit is approximately 0.25V (up to 0.5V in starter motor circuits).
    For the earth part of the circuit, the voltage drop should be 0V, or very close to it.

You can read more about Gustav Kirchhoff on Wikipedia

You can read more about Kirchhoff's circuit laws on Wikipedia

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Provider of microcontroller chips. They are now part of the Atmel group and Microchip Technology Inc.

You can read more about these companies here.

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Electromagnetic compatibility (EMC) refers to the unintentional generation, propagation and reception of electromagnetic energy which may cause unwanted effects such as electromagnetic interference (EMI) or even physical damage in operational equipment.

EMC is the correct operation of different  electronic equipment in a common electromagnetic environment.

You can read more about EMC on Wikipedia

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A shunt resistor is a usually small value resistor placed in series with a load.

You will come across shunt resistors in DMM ammeters, or in electronic chips that need to monitor how much electricity is flowing in a particular circuit.

Shunt resistors are normally small value resistors, say 30mΩ (30 milliohms or 0.03 Ohms).

The reason they have such small values is that we don't want to interfere with the circuits in which we place them. What we do is we measure the voltage drop across the small resistance. Then, using Ohm's Law, we know the resistance and we've measured the voltage drop, therefore we can calculate the current flowing through the resistor:

I=V/R

This allows us to calculate the current flowing through a circuit, without having to pass that current through an ammeter - we just measure the voltage drop across the resistor and divide that by the value of that resistor (in this case, 30 milliohms, 0.03 ohm).

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James Watt

The Watt is the measurement of power, and gets its name from James Watt. This is the modern metric way of measuring power.

The old way of doing it was to measure the power of something relative to the power of a horse:

  • HP: Throughout the United Kingdom, and in many other parts of the world - horsepower
  • CV: In France and other areas of the world under French influence, 'cheval vapeur', or 'steam horse'
  • PS: Often referred to as 'the metric horsepower', this is a German version of measuring power and means 'the strength of a horse'

If a force of 1 Newton moves an object through a distance of 1 metre in 1 second, then 1 Watt of power is said to have been expended.

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In the SI, there are 7 base units of measurement. The ones we come across in the phase 2 course are:

Other units of measurement such as those for torque, speed, power etc. are all based on SI units of measurement, so they are said to be 'base derived' units of measurement.

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