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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 – Fundamentals of ElectricityClass 3 – Fundamentals of Electricity
Bob Solosko W1SRBBob Solosko W1SRB
Fundamentals of ElectricityFundamentals of Electricity
• All materials are made up of atoms• Atoms are composed of protons, neutrons and electrons
• electrons have a positive charge• protons have a negative charge
• In some materials, electrons are held tightly to the atom
• these materials are insulators• examples:
• wood, ceramics, plastics
• In some materials, electrons are held loosely to the atom are free to move around
• these materials are conductors• examples:
• copper, silver, aluminum
ProtonsAnd
Neutorns
Electrons
Electricity is about how electrons flows through materials
Fundamentals of ElectricityFundamentals of Electricity
Controlling the flow of electrons is the
foundation for the operation of – Radios
– Ipods
– Computers
– Telephones
– Recorders
– Stereos
– House lights
Fundamentals of ElectricityFundamentals of Electricity
• There are three characteristics to electricity:– Electromotive Force– Current– Resistance
• All three must be present for electrons to flow
Fundamentals of ElectricityFundamentals of Electricity
Electromotive Force (EMF or E)– “electro”: electrons– “motive”: movement– “force”: the push
• Electromotive force is the push that causes electrons to move through a conductor
• Measured in volts
• Usually referred to as voltage
Fundamentals of ElectricityFundamentals of Electricity
Current (I)
• Current is the amount of electrons that flow through a conductor over time
• Measured in amperes – i.e., amps
Fundamentals of ElectricityFundamentals of Electricity
Resistance (R)
• A material's opposition to the flow of electric current; measured in ohms.
• Measured in ohms
• All materials, even very good conductors have some resistance
Fundamentals of ElectricityFundamentals of Electricity
• Electrons are confined to conductors, i.e., wires
• Electrons flow only through a closed circuit
– Similar to the flow of water in the pipes of a closed hot water
heating system
– Like a pump that provides the force to push water through
the pipe, a battery provides the electrical push, i.e., voltage,
to push electrons through the wire
Fundamentals of ElectricityFundamentals of Electricity
• Electrons are confined to conductors, i.e., wires
• Electrons flow only through a closed circuit
Closed circuit, current flows Open circuit, no current flows
switch switch
Fundamentals of ElectricityFundamentals of Electricity
• Electrical circuits
switch
battery
Resistance(resistor)
voltage
current
Fundamentals of ElectricityFundamentals of Electricity
Relationship between Voltage (E), Current (I) and Resistance (R)
• It takes a certain force (i.e., voltage) to get a certain amount of current (amps) to flow against a specific reststance (ohms)
• A greater resistance requires a greater force (i.e., higher voltage) to get the same amount of current to flow
Fundamentals of ElectricityFundamentals of Electricity
Relationship between Voltage (E), Current (I) and Resistance (R)
Ohm’s Law
Voltage = Current x Resistance
E = I x RVolts = amps x ohms
Fundamentals of ElectricityFundamentals of Electricity
Relationship between Voltage (E), Current (I) and Resistance (R)
Ohm’s Law
Current = Voltage/ResistanceI = E / R
Resistance = Voltage/CurrentR = E / I
Fundamentals of ElectricityFundamentals of Electricity
Ohm’s Law - Summary
• E is voltage– Units - volts
• I is current– Units - amperes
• R is resistance– Units - ohms
• R = E/I• I = E/R• E = I x R
Fundamentals of ElectricityFundamentals of Electricity
battery
Resistancevoltage
current
10 V5 Ω
2 A
• Electrical circuits – Ohms law
E = I x RI = E / RR = E / I
If voltage V = 10 volts (10 V) and resistance R = 5 ohm (1 Ω)
Then current I = E / R = 10 / 5 = 2 amps (2 A)
Fundamentals of ElectricityFundamentals of Electricity
• Electrical circuits – Ohms law
E = I x RI = E / RR = E / I
If voltage V = 10 volts (10 V) and resistance R = 5 ohm (1 Ω)
Then current I = E / R = 10 / 5 = 2 amps (2 A)
If voltage = 10 V and current = 20 A
Then resistance R = E / I = 10 / 20 = ½ Ω
battery
Resistancevoltage
current
10 V1/2 Ω
20 A
Fundamentals of ElectricityFundamentals of Electricity
• Electrical circuits – Ohms law
E = I x RI = E / RR = E / I
If voltage V = 10 volts (10 V) and resistance R = 5 ohm (1 Ω)
Then current I = E / R = 10 / 5 = 2 amps (2 A)
If voltage = 10 V and current = 20 A
Then resistance R = E / I = 10 / 20 = ½ Ω
If resistance = 100 Ω and current = 3 A
Then voltage V = I x R = 3 x 100 = 300 V
battery
Resistancevoltage
current
300 V100 Ω
3 A
Fundamentals of ElectricityFundamentals of Electricity
• Electrical circuits – Ohms law
battery
Resistancevoltage
current
300 V100 Ω
3 A
Fundamentals of ElectricityFundamentals of Electricity
• Electrical circuits – Ohms law
battery
Resistancevoltage
current
300 V100 Ω
3 A300 V 300 V
The voltage across the resistor is the same as the voltage across the battery
Fundamentals of ElectricityFundamentals of Electricity
• Electrical circuits – Ohms law
battery
Resistancevoltage
current
300 V100 Ω
3 A
Fundamentals of ElectricityFundamentals of Electricity
• Electrical circuits – Ohms law
battery
Resistancevoltage
current
300 V100 Ω
3 A
3 A
3 A
The current is the same anywhere in the circuit
Fundamentals of ElectricityFundamentals of Electricity
Power
• Moving electrons do work and expend energy:
– generate heat
– generate light
– run motors
– generate and receive radio signals
– compute
• Power is the rate at which electrical energy is generated or consumer
– measured in the units of Watts
• Power = voltage x current P = E x I
Fundamentals of ElectricityFundamentals of Electricity
Power• Power = voltage x current
P = E x II = P/EE = P/I
• Example 1: 60 watt light bulb– E = 120v, P = 60w, I = ?, R = ?
120 V I
60w bulb
Fundamentals of ElectricityFundamentals of Electricity
Power• Power = voltage x current
P = E x II = P/EE = P/I
• Example 1: 60 watt light bulb– E = 120v, P = 60w, I = ?, R = ?
I = P/E = 60/120 = ½ AR = E/I = 120/½ = 240Ω
120 V I
battery
Resistancevoltage
current
300 V100 Ω
60w bulb
• Example 2: – E = 300v, R = 100Ω, I = ?, P = ?
I = E/R = 300/100 = 3AP = E x I = 300/3 = 300w
Fundamentals of ElectricityFundamentals of Electricity
Types of Current
• When current flows in only one direction, it is called direct current (DC).– batteries are a common source of DC.– most electronic devices are powered by DC.
• When current flows alternatively in one direction then in the opposite direction, it is called alternating current (AC).– your household current is AC.– radio waves are AC
Fundamentals of ElectricityFundamentals of Electricity
Electrical Circuits
• Series circuit – one and only one path for current flow
• Parallel circuit– alternative paths for current flow
battery
Resistor orother component
current
Resistor orother component
battery
Resistor orother component
current
Fundamentals of ElectricityFundamentals of Electricity
Components: the resistor
• restricts (limits) the flow of current through it
• unit of resistance: ohm (Ω)
• (also dissipates energy as heat)– incadescent lightbulbs– electric stoves
• Circuit Symbol
Fundamentals of ElectricityFundamentals of Electricity
Components: the resistor
• restricts (limits) the flow of current through it
• unit of resistance: ohm (Ω)
• (also dissipates energy as heat)– incadescent lightbulbs– electric stoves
• A resistor for which the resistance can be changed is a variable resistor or potentiometer
• Circuit Symbol
variableresistor
potentiometer
Fundamentals of ElectricityFundamentals of Electricity
Components: the resistor
• restricts (limits) the flow of current through it
• unit of resistance: ohm (Ω)
• (also dissipates energy as heat)– incadescent lightbulbs– electric stoves
• A resistor for which the resistance can be changed is a variable resistor or potentiometer
• Circuit Symbol
Fundamentals of ElectricityFundamentals of Electricity
Components: the battery
• source of DC voltage
• stores energy
• provides energy to a circuit
• Circuit Symbol
Fundamentals of ElectricityFundamentals of Electricity
• temporarily stores electrons and electric current– stores energy in an
electrostatic field
• Unit of capacitance: farad
• composed of parallel metal plates with a non-conductive material (dielectric) in between– dielectric can be air, plastic,
glass, etc.
• A capacitor for which the capacitance can be changed is a variable capacitor
Components: the capacitor• Circuit Symbol
Fundamentals of ElectricityFundamentals of Electricity
• Unit of capacitance: farad– a coulomb is a unit of electrical charge– 1 coulomb = 6,250,000,000,000,000,000 electrons– 1 farad is 1 coulomb/volt
Components: the capacitor
switch
Fundamentals of ElectricityFundamentals of Electricity
• Unit of capacitance: farad– a coulomb is a unit of electrical charge– 1 coulomb = 6,250,000,000,000,000,000 electrons– 1 farad is 1 coulomb/volt
Components: the capacitor
switch
Fundamentals of ElectricityFundamentals of Electricity
• Unit of capacitance: farad– a coulomb is a unit of electrical charge– 1 coulomb = 6,250,000,000,000,000,000 electrons– 1 farad is 1 coulomb/volt
Components: the capacitor
switch
Fundamentals of ElectricityFundamentals of Electricity
• Unit of capacitance: farad– a coulomb is a unit of electrical charge– 1 coulomb = 6,250,000,000,000,000,000 electrons– 1 farad is 1 coulomb/volt
Components: the capacitor
switch
Fundamentals of ElectricityFundamentals of Electricity
• Unit of capacitance: farad– a coulomb is a unit of electrical charge– 1 coulomb = 6,250,000,000,000,000,000 electrons– 1 farad is 1 coulomb/volt
Components: the capacitor
switch
Note: once the capacitor is charged, no more current flows, and the capacitor acts like an open circuit (an open switch)
Fundamentals of ElectricityFundamentals of Electricity
• Unit of capacitance: farad– a coulomb is a unit of electrical charge– 1 coulomb = 6,250,000,000,000,000,000 electrons– 1 farad is 1 coulomb/volt
Components: the capacitor
switch
Fundamentals of ElectricityFundamentals of Electricity
• Unit of capacitance: farad– a coulomb is a unit of electrical charge– 1 coulomb = 6,250,000,000,000,000,000 electrons– 1 farad is 1 coulomb/volt
Components: the capacitor
switch
Fundamentals of ElectricityFundamentals of Electricity
• Unit of capacitance: farad– a coulomb is a unit of electrical charge– 1 coulomb = 6,250,000,000,000,000,000 electrons– 1 farad is 1 coulomb/volt
Components: the capacitor
switch
Fundamentals of ElectricityFundamentals of Electricity
• Unit of capacitance: farad– a coulomb is a unit of electrical charge– 1 coulomb = 6,250,000,000,000,000,000 electrons– 1 farad is 1 coulomb/volt
Components: the capacitor
switch
Fundamentals of ElectricityFundamentals of Electricity
• Unit of capacitance: farad– a coulomb is a unit of electrical charge– 1 coulomb = 6,250,000,000,000,000,000 electrons– 1 farad is 1 coulomb/volt
Components: the capacitor
switch
~AC voltage
Fundamentals of ElectricityFundamentals of Electricity
• Unit of capacitance: farad– a coulomb is a unit of electrical charge– 1 coulomb = 6,250,000,000,000,000,000 electrons– 1 farad is 1 coulomb/volt
Components: the capacitor
switch
~AC voltage
Note: a capacitor allows AC current to flow
Fundamentals of ElectricityFundamentals of Electricity
• Capacitive reactance (XC)
– the opposition to alternating current due to capacitance
– unit of capacitive reactance: ohms
– is inversely proportional to the signal frequency and the
capacitance
– XC = - 1 / (2fC)
• Note: if f = 0, i.e. DC current, XC = ∞, i.e., an open circuit
Components: the capacitor
Fundamentals of ElectricityFundamentals of Electricity
• stores electric current– stores energy in a magnetic
field– any wire with a current
flowing through it creates a magnetic field
• unit of inductance: henry
• magnetic field is strengthened by coiling wire, i.e., inductance is increases
• an inductor for which the inductance can be changed is a variable inductance
• An inductor may have an iron core to increase the inductance
• Circuit Symbol
Components: the inductor
Fundamentals of ElectricityFundamentals of Electricity
• Inductive reactance (XL)
– the opposition to alternating current due to inductance
– unit of inductance reactance: ohms
– is proportional to the signal frequency and the inductance
– XL = + 2fL
• Note: if f = 0, i.e. DC current, XL = 0, i.e., an short circuit
Components: the inductor
Fundamentals of ElectricityFundamentals of Electricity
• Impedance is the total opposition to alternating current due to
reistance, capacitance and inductance
– unit of impedance: ohms
– Z = √ R2 + (XC + XL)2
• Resonance:
When XC = XL,
Then Z = R
Impedance (Z):
~AC voltage
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
• Circuit Symbol
Components: the transistor
B
E
C
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
• Circuit Symbol
Components: the transistor
B
E
C
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
• Circuit Symbol
Components: the transistor
B
E
C
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
• Circuit Symbol
Components: the transistor
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
Components: the integrated circuit
• Circuit Symbol
Fundamentals of ElectricityFundamentals of Electricity
• Allows current to flow in only one direction
• Circuit SymbolComponents: 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.
• Circuit Symbol
Components: fuses and circuit breakers
• Special type of diode that emits light when current passes through it
Components: light emiting diode (LED)
Fundamentals of ElectricityFundamentals of Electricity
Other Circuit Symbols:
Fundamentals of ElectricityFundamentals of Electricity
Circuit Diagrams: examples
Amplifier
Fundamentals of ElectricityFundamentals of Electricity
Light control Antenna tuner
Power supply – converts 120VAC to DC
Fundamentals of ElectricityFundamentals of Electricity
• resistor values may be ohms (Ω), kilo ohms (kΩ) or mega ohms (MΩ)
• capacitor values typically are microfarads (μf) or pico farads (pf)
• inductance values are typically milli henrys (mh) or micro henrys (μh)
• frequencies are typically kilo hertz (kHz) or mega Hertz (MHz)
• voltage is often volts (V) milli volts (mV) or micro volts (μV)
• current is often amps (A), milli amps (mA) or micro amps (μA)
Very Large and Very Small Numeric Values: Units
Fundamentals of ElectricityFundamentals of Electricity
• decibels are used to compare values that vary over a very large range
– signal levels, amplifier gain, sound levels
• decibles compare values on a logrithmic scale
• 3 dB is a factor of 2
– a 3 dB gain in an amplifier means that the output level is twice the input level
• 10 dB is a factor of 10
– a 10 dB gain in an amplifier means that the output level is 10 times the input level
• 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
Very Large and Very Small Numeric Values: decibels (dB)
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