1. Fundamentals of Electricity Franklin County Amateur Radio Club Technician Class License Course Class 2a – Fundamentals of Electricity, Part 1 Bob Solosko W1SRB Edited by Al Woodhull, N1AW

2. 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

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

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

5. 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

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

7. 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

8. 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

9. 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

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

11. 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

12. 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

13. 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

14. 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

15. 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)

16. 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

17. 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

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

19. 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

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

21. 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

22. 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

23. 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

24. 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

25. 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