franklin county amateur radio club technician class license course
DESCRIPTION
Franklin County Amateur Radio Club Technician Class License Course Class 3 – Electrical Components and Units Bob WA1QKT (originally by W1SRB). Resistance. Hydraulic Resistance. Resistor. Restricts the flow of current Unit of resistance: Ohm ( Ω ) Dissipates power as heat - PowerPoint PPT PresentationTRANSCRIPT
Fundamentals of ElectricityFundamentals of Electricity
Franklin County Amateur Radio ClubFranklin County Amateur Radio Club
Technician Class License CourseTechnician Class License Course
Class 3 – Electrical Components and UnitsClass 3 – Electrical Components and Units
Bob WA1QKTBob WA1QKT(originally by W1SRB)(originally by W1SRB)
Fundamentals of ElectricityFundamentals 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 = I x R
Variable resistor or potentiometerFixed-value resistor
Fundamentals of ElectricityFundamentals of Electricity
Battery
• Source of DC voltage and energy
• Nickel Cadmium Cell V = 1.2V
Fundamentals of ElectricityFundamentals of Electricity
• 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
Capacitor
Fundamentals of ElectricityFundamentals 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 ElectricityFundamentals of Electricity
• 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
Inductor
Fundamentals of ElectricityFundamentals 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 ElectricityFundamentals of Electricity
• 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,
so Z = R
(maximum current in series RLC)
Impedance (Z):
~AC voltage
Fundamentals of ElectricityFundamentals of Electricity
battery
Resistor orother component
Resistor orother componentElectrical Circuits
• Series circuit • Same current in all parts• May be different voltages
• Parallel circuit• Same voltage on all parts• May be different currents
battery
Resistor orother component
Fundamentals of ElectricityFundamentals of Electricity
• 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
Transistor
B
E
C
Fundamentals of ElectricityFundamentals of Electricity
FET : Field Effect Transistor
GateSourceDrain
Fundamentals of ElectricityFundamentals of Electricity
• 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
Integrated Circuit
Fundamentals of ElectricityFundamentals of Electricity
• Allows current to flow in only one direction
Components: diode
• interrupts the flow of current if the current exceeds some value
• Fuses blow – one time protection.
• Circuit breakers trip – can be reset and reused.
Components: fuses and circuit breakers
• Special type of diode that emits light when current passes through it
Components: light emiting diode (LED)
Anode Cathode
Fundamentals of ElectricityFundamentals of Electricity
Light control Antenna tuner
Power supply – converts 120VAC to DC
Fundamentals of ElectricityFundamentals of Electricity
Units
Current Amperes A
Voltage Volts V
Resistance Ohms Capacitance Farads F
Inductance Henrys H
Frequency Hertz Hz
Fundamentals of ElectricityFundamentals of Electricity
Very Large and Very Small Numeric Values: Units
Fundamentals of ElectricityFundamentals of Electricity
• 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
• a 3 dB gain in an amplifier means that the output power is 2 x the input power
• 10 dB is a factor of 10
• 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
Power Ratios: decibels (dB)