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Fundamentals of Electricity Franklin County Amateur Radio Club Technician Class License Course Class 3 – Electrical Components and Units Bob WA1QKT (originally by W1SRB) Fundamentals of Electricity Hydraulic Resistance Resistance Fundamentals of Electricity Fundamentals of Electricity Resistor • Restricts the flow of current • Unit of resistance: Ohm (Ω) • Dissipates power as heat • incandescent lightbulbs • electric stoves • Obeys Ohm’s Law: V=IxR Fixed-value resistor Variable resistor or potentiometer Fundamentals of Electricity Battery • Source of DC voltage and energy • Nickel Cadmium Cell V = 1.2V Fundamentals of Electricity Fundamentals of Electricity Capacitor • stores electric charge • stores energy in an electric field • Farad • parallel metal plates with a non-conductive material (dielectric) in between • dielectric can be air, plastic, glass, etc. • variable capacitor Fundamentals of Electricity • Capacitive reactance (XC) • the opposition to alternating current due to Capacitance • Ohms • XC gets smaller as f goes up, and as C goes • Passes AC, Blocks DC ( parallel plates is DC open circuit) Fundamentals of Electricity Inductor • Stores magnetic flux • Stores energy in magnetic field • any wire with a current flowing through it creates a magnetic field • Henry • magnetic field is strengthened by coiling wire, i.e., inductance increases • Variable inductance • Iron core increases the inductance Fundamentals of Electricity • Inductive reactance (XL) • the opposition to alternating current due to Inductance • Ohms • XL gets bigger as f goes up, and as L goes up • Blocks AC, Passes DC ( coil of wire is DC short circuit) Fundamentals of Electricity Impedance (Z): • Impedance is the total opposition to alternating current due to Resistance, Capacitance and Inductance • Ohms • Resonance: Because C, L have opposite phase shifts, When XC = XL, ~ They cancel, AC voltage so Z = R (maximum current in series RLC) Fundamentals of Electricity Electrical Circuits • Series circuit • • • Resistor or other component Same current in all parts May be different voltages Resistor or other component battery Resistor or other component Parallel circuit • • Same voltage on all parts May be different currents battery Fundamentals of Electricity Transistor • • controls the flow of current • like an electronically controlled valve. • like the faucet in your sink used to amplify a signal or as an on-off switch • A small current or voltage on the Base (B) lead causes a large change in the current flowing between the Emitter (E)” and Collector (C) leads C B E Fundamentals of Electricity FET : Field Effect Transistor Gate Source Drain Fundamentals of Electricity Integrated Circuit • a collection of components contained in one device • replaces many individual components • a “black-box” for a specific function • examples: • • • • • amplifier switch voltage regulator mixer display controller Fundamentals of Electricity Components: diode • Allows current to flow in only one direction Anode Cathode Components: light emiting diode (LED) • Special type of diode that emits light when current passes through it Components: fuses and circuit breakers • interrupts the flow of current if the current exceeds some value • Fuses blow – one time protection. • Circuit breakers trip – can be reset and reused. Fundamentals of Electricity Light control Antenna tuner Power supply – converts 120VAC to DC Fundamentals of Electricity Units Current Amperes A Voltage Volts V Resistance Ohms Capacitance Farads F Inductance Henrys H Frequency Hertz Hz Fundamentals of Electricity Very Large and Very Small Numeric Values: Units Fundamentals of Electricity Power Ratios: decibels (dB) • decibels are used to compare power over a very large range • signal levels, amplifier gain, sound levels • decibels compare powers on a logarithmic scale • 3 dB is a factor of 2 • • 10 dB is a factor of 10 • • a 3 dB gain in an amplifier means that the output power is 2 x the input power a 10 dB gain in an amplifier means that the output power is 10 x the input power decibels add: • 3 dB = 2 times • 6 dB = 2 x 2 = 4 times • 9 dB = 2 x 2 x 2 = 8 times • 12 dB = 2 x 2 x 2 x 2 = 16 times • 10 dB = 10 times • 20 dB = 10 x 10 = 100 times • 30 dB = 10 x 10 x 10 = 1000 times