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3. Foundation Course Technical Basics 1 EKRS Karl Davies Introduction 2 Important to appreciate and understand basic electric and radio frequency symbols, units and concepts You don’t need to be a circuit designer/builder! that comes from experience and as you progress through the Intermediate and Advanced Courses For Foundation it important to understand:- Conductors and Insulators Volts, Current, Power and Resistance Frequencies and Wavelengths Basic symbols/diagrams Conductors & Insulators 3 Conducts permit the flow of electric current Examples: Copper, Brass etc Metallic Conductors permit electrons to flow easily Beware of poor/oxidised connections (eg on Aluminium, Steel) Insulators don’t permit electron flow and exhibit high resistance. Examples: Plastics, wood, rubber, glass, ceramics Note that water is a conductor (esp. when impure), and that wet insulators can therefore conduct on their surface This can be a risk for outdoor/portable equipment Electrical Units 4 Quantity Voltage, V Current, I Resistance, R Power, P Frequency, f Wavelength, Unit Volt Amp Ohm Watt Hertz Metre Symbol V A W Hz m Note-1: Resistance is the opposition to current flow Note-2: Voltage is sometimes referred to as Potential Difference Unit Prefixes 5 Factor millionths thousandths thousands millions Prefix micro milli kilo Mega Symbol or u m k M Examples: 4.7k= 4700 1500mA = 1.5A 0.6MHz = 600kHz 500mW = 0.5W Power 6 P Watts V Volts I Amps Relates Power, P Voltage, V P=VxI V=P/I I=P/V Current, I Ohms Law 7 V Volts I Amps R Ohms Relates Voltage, V Current, I Resistance, R V=IxR I=V/R R=V/I DC & AC Power 8 DC - Direct Current Cells/Batteries provide a source of DC power Direct Current flows in a single direction AC - Alternating Current + • AC is easier to generate and transform - • Mains is 50Hz AC. Radio Frequencies (RF) use High Frequency AC • Simple items such as Filament Light Bulbs work with AC and DC, but many electronic components are sensitive to the direction of current Frequency & Wavelength 9 In air the velocity, v of radio waves is a constant ( ~3x108m/s) So if the frequency increases, the wavelength decreases, and vice versa, determined by: v = f x A 1MHz to 1000MHz conversion chart, and frequency allocation table is available Frequency, f v Wavelength, v m/s f Hertz metres Circuit Symbols 10 Also need to recognise symbols for Antenna Switches, Earths, Crystals etc, etc Earth + Cell Battery - Switch SPST SPST - single-pole, single-throw Resistor Fuse Crystal Loudspeaker Lamp Microphone