Transcript Components and Units - Franklin County Amateur Radio Club

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