Franklin County Amateur Radio Club Technician Class License Course

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

B

E

C


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


Units

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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