Current measured in Amps (A), symbol: I
Resistance measured in Ohms (upside-down horse-shoe shape), symbol: R
Power measured in Watts (W), symbol: P
Voltage measured in Volts (V), symbol: V
Electrons which carry the charge flow from positive to negative in a circuit. The energy loss measured from the circuit is known as potential difference. This allows us to calculate the voltage. The more voltage there is then essentially the more power there is.
We now have to know some details regarding lengths such as 1cm= 0.01 of a meter and 1mm=0.001 of a meter. This is to enable us to do some calculations in the exam. Three important amounts are:
Milli = 1/1000 or 0.001m
Kilo = 1000 or K
Mega = 1million or M
Have a look at a simple circuit to understand the symbols for battery, light bulb, switch and resistor.
Now, this is where I got a little stuck in mud. Fundamental point to note is that Current is the rate of flow and Voltage is the pressure. We will have to calculate either Power, resistance, current or voltage and so have to use the triangle symbols to help.
Cover the symbol you want and multiply or divide the alternate two symbols for your answer.
There was a brief mention of Alternating Current (AC) and Direct Current which are quite self explanatory.
Next was the mention of Waves(upside-down y) and Frequency (f). Best to view a waveform for this one! The cycles in a wave are known as frequency per second and are denoted at Hertz or Hz. We need to know the ranges in frequency and so here they are:
300KHz - 3MHz = MF medium frequency
3MHz - 30MHz = HF high frequency
30MHz - 300MHz = VHF very high frequency
300MHz - 3000MHz = UHF ultra high frequency
For sonic applications; the shorter the wave length, the higher the frequency.
In the exam we will be given several documents,one of which is a chart stating (in binary) length vs. frequency. Knowing how to read this means we can work out who uses the different ranges e.g. emergency services.
what what eh?
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