Fundamentals of Electricity Franklin County Amateur Radio Club Technician Class License Course Class 3 – Fundamentals of Electricity Bob Solosko W1SRB

Fundamentals 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 Protons And Neutorns Electrons Electricity is about how electrons flows through materials

Fundamentals of Electricity Controlling the flow of electrons is the foundation for the operation of –Radios –Ipods –Computers –Telephones –Recorders –Stereos –House lights

Fundamentals of Electricity There are three characteristics to electricity: –Electromotive Force –Current –Resistance All three must be present for electrons to flow

Fundamentals 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 Electricity Current ( I ) Current is the amount of electrons that flow through a conductor over time Measured in amperes –i.e., amps

Fundamentals 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 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 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

Fundamentals of Electricity Electrical circuits switch battery Resistance (resistor) voltage current

Fundamentals 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 Electricity Relationship between Voltage (E), Current ( I ) and Resistance ( R ) Ohm’s Law Voltage = Current x Resistance E = I x R Volts = amps x ohms

Fundamentals of Electricity Relationship between Voltage (E), Current ( I ) and Resistance ( R ) Ohm’s Law Current = Voltage/Resistance I = E / R Resistance = Voltage/Current R = E / I

Fundamentals 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 Electricity battery Resistance voltage current 10 V 5 Ω 2 A Electrical circuits – Ohms law E = I x R I = E / R R = 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 Electricity Electrical circuits – Ohms law E = I x R I = E / R R = 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 Resistance voltage current 10 V 1/2 Ω 20 A

Fundamentals of Electricity Electrical circuits – Ohms law E = I x R I = E / R R = 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 Resistance voltage current 300 V 100 Ω 3 A

Fundamentals of Electricity Electrical circuits – Ohms law battery Resistance voltage current 300 V 100 Ω 3 A

Fundamentals of Electricity Electrical circuits – Ohms law battery Resistance voltage current 300 V 100 Ω 3 A 300 V The voltage across the resistor is the same as the voltage across the battery

Fundamentals of Electricity Electrical circuits – Ohms law battery Resistance voltage current 300 V 100 Ω 3 A

Fundamentals of Electricity Electrical circuits – Ohms law battery Resistance voltage current 300 V 100 Ω 3 A The current is the same anywhere in the circuit

Fundamentals 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 Electricity Power Power = voltage x current P = E x I I = P/E E = P/I Example 1: 60 watt light bulb –E = 120v, P = 60w, I = ?, R = ? 120 V I 60w bulb

Fundamentals of Electricity Power Power = voltage x current P = E x I I = P/E E = P/I Example 1: 60 watt light bulb –E = 120v, P = 60w, I = ?, R = ? I = P/E = 60/120 = ½ A R = E/I = 120/½ = 240Ω 120 V I battery Resistance voltage current 300 V 100 Ω 60w bulb Example 2: – E = 300v, R = 100Ω, I = ?, P = ? I = E/R = 300/100 = 3A P = E x I = 300/3 = 300w

Fundamentals 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 Electricity Electrical Circuits Series circuit –one and only one path for current flow Parallel circuit –alternative paths for current flow battery Resistor or other component current Resistor or other component battery Resistor or other component current

Fundamentals 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 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 variable resistor potentiometer

Fundamentals 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 Electricity Components: the battery source of DC voltage stores energy provides energy to a circuit Circuit Symbol

Fundamentals 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 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 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 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 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 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 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 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 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 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 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 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 Electricity Capacitive reactance (X C ) –the opposition to alternating current due to capacitance –unit of capacitive reactance: ohms –is inversely proportional to the signal frequency and the capacitance – X C = - 1 / (2  fC) Note: if f = 0, i.e. DC current, X C = ∞, i.e., an open circuit Components: the capacitor

Fundamentals 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 Electricity Inductive reactance (X L ) –the opposition to alternating current due to inductance –unit of inductance reactance: ohms –is proportional to the signal frequency and the inductance – X L = + 2  fL Note: if f = 0, i.e. DC current, X L = 0, i.e., an short circuit Components: the inductor

Fundamentals of Electricity Impedance is the total opposition to alternating current due to reistance, capacitance and inductance –unit of impedance: ohms –Z = √ R 2 + (X C + X L ) 2 Resonance: When XC = XL, Then Z = R Impedance (Z): ~ AC voltage

Fundamentals 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 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 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 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 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 Electricity Allows current to flow in only one direction Circuit Symbol 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. 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 Electricity Other Circuit Symbols:

Fundamentals of Electricity Circuit Diagrams: examples Amplifier

Fundamentals of Electricity Light control Antenna tuner Power supply – converts 120VAC to DC

Fundamentals 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 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)