Franklin County Amateur Radio Club Technician Class License Course

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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)

ResistanceHydraulic Resistance

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

Battery

• Source of DC voltage and energy

• Nickel Cadmium Cell V = 1.2V

• 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

• 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)

• 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

• 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)

• 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

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

• 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

FET : Field Effect Transistor

GateSourceDrain

• 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

• 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

Light control Antenna tuner

Power supply – converts 120VAC to DC

Current Amperes A

Voltage Volts V

Resistance Ohms Capacitance Farads F

Inductance Henrys H

Frequency Hertz Hz

Very Large and Very Small Numeric Values: Units

• 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)

Franklin County Amateur Radio Club Technician Class License Course

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