Franklin County Amateur Radio Club Technician Class License Course

1. 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. Electrons Protons And Neutorns • 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 Electricity is about how electrons flows through materials

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

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

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

7. 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. 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. switch switch • Electrons are confined to conductors, i.e., wires • Electrons flow only through a closed circuit Closed circuit, current flows Open circuit, no current flows

10. switch Resistance (resistor) voltage battery current • Electrical circuits

11. 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. 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. 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. 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. 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) Resistance voltage 5 Ω 10 V battery current 2 A

16. Resistance voltage 1/2 Ω 10 V battery current 20 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) If voltage = 10 V and current = 20 A Then resistance R = E / I = 10 / 20 = ½ Ω

17. Resistance voltage 100 Ω 300 V battery current 3 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) 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

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

19. Resistance voltage 100 Ω 300 V battery current 3 A • Electrical circuits – Ohms law 300 V 300 V The voltage across the resistor is the same as the voltage across the battery

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

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

22. 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. I 120 V • 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 = ? Power 60w bulb

24. I 120 V • 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 Power 60w bulb • Example 2: • E = 300v, R = 100Ω, I = ?, P = ? I = E/R = 300/100 = 3A P = E x I = 300/3 = 300w Resistance voltage 100 Ω 300 V battery current

25. 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