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Technician Licensing Class “Chapter 3”

Technician Licensing Class “Chapter 3”. “ Sipping from a Fire Hose 101”. Chapter 3 Contents. Electricity Components and Units Types of Radios and Radio Circuits. Electricity. Voltage and Current Circuits Resistance (including Ohm’s Law) Power AC and DC. Voltage.

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Technician Licensing Class “Chapter 3”

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  1. Technician Licensing Class“Chapter 3” “ Sipping from a Fire Hose 101”

  2. Chapter 3 Contents • Electricity • Components and Units • Types of Radios and Radio Circuits

  3. Electricity • Voltage and Current • Circuits • Resistance (including Ohm’s Law) • Power • AC and DC

  4. Voltage • Symbol: “E” or “e” • Unit of Measure: “Volt” • Measurement Device: “Voltmeter” • Can be positive or negative • Measured between two points referenced to ground (usually) or to each other • Is a measure of “pressure” • aka: Electrical potential

  5. Current • Symbol: “I” or “i” • Unit of Measure: “Ampere” or “amp” • Measures flow of current through something • Measurement Device: “Ammeter”

  6. Quantity Amount of charge transmitted in one second by a constant flow of 1 ampere • Unit of Measure: “Coulomb” • Number of Electrons flowing per second 6.25 x 1018 Electrons per second Equals one ampere • An ampere is like a cord of firewood • A coulomb is like the number of pieces of firewood in a cord

  7. SERIES PARALLEL Circuits AMMETER – connect in Series VOLTMETER – connect in Parallel

  8. Open Circuit Short Circuit Circuits

  9. T5A01 Electrical current is measured in which of the following units? • Volts • Watts • Ohms • Amperes

  10. T5A03 What is the name for the flow of electrons in an electric circuit? • Voltage • Resistance • Capacitance • Current

  11. T5A05 What is the electrical term for the electromotive force (EMF) that causes electron flow? • Voltage • Ampere-hours • Capacitance • Inductance

  12. T5A11 What is the basic unit of electromotive force? • The volt • The watt • The ampere • The ohm

  13. T7D01 Which instrument would you use to measure electric potential or electromotive force? • An ammeter • A voltmeter • A wavemeter • An ohmmeter

  14. T7D02 What is the correct way to connect a voltmeter to a circuit? • In series with the circuit • In parallel with the circuit • In quadrature with the circuit • In phase with the circuit

  15. T7D03 How is an ammeter usually connected to a circuit? • In series with the circuit • In parallel with the circuit • In quadrature with the circuit • In phase with the circuit

  16. T7D04 Which instrument is used to measure electric current? • An ohmmeter • A wavemeter • A voltmeter • An ammeter

  17. Meters • Voltmeter - Electromotive Force • Ammeter - Current • Ohmmmeter - Resistance • Multimeter • aka VOM (Volt-Ohm-Meter) • Aaka – DVM (Digital Volt Meter) • Actually measures all three

  18. T7D: Basic repair and testing; soldering, use of a voltmeter,ammeter and ohmmeter • T7D3 An ammeter is connected to a circuit in series with the circuit. • T7D4 An ammeter is an instrument used to measure electric current.

  19. T7D06 Which of the following might damage a multimeter? • Measuring a voltage too small for the chosen scale • Leaving the meter in the milliamps position overnight • Attempting to measure voltage when using the resistance setting • Not allowing it to warm up properly

  20. T7D07 Which of the following measurements are commonly made using a multimeter? • SWR and RF power • Signal strength and noise • Impedance and reactance • Voltage and resistance

  21. T7D10 • What is probably happening when an ohmmeter, connected across a circuit, initially indicates a low resistance and then shows increasing resistance with time? • The ohmmeter is defective • The circuit contains a large capacitor • The circuit contains a large inductor • The circuit is a relaxation oscillator

  22. T7D11 Which of the following precautions should be taken when measuring circuit resistance with an ohmmeter? • Ensure that the applied voltages are correct • Ensure that the circuit is not powered • Ensure that the circuit is grounded • Ensure that the circuit is operating at the correct frequency

  23. Resistance • Impedes the flow of electrons to some degree • Ohm – Unit of Measure • Symbol = “R” • Represented by Ω (Greek Letter Omega)

  24. Resistance • Conductor • Let electrons flow easily • Low resistance • Copper, Gold Aluminium • Insulator • Prevent flow of electrons • Very high resistance • Glass, rubber ceramics, paper, dry wood

  25. T5D Ohm’s Law T5D1 The formula CURRENT (I) EQUALS VOLTAGE (E) DIVIDED BY RESISTANCE (R) IS USED TO CALCULATE CURRENT in a circuit. E is for Voltage, I is for current, and R is for resistance The math is easy Two known numbers are given, solve for the unknown Cover up the unknown and plug the numbers in the other two I = E / R Finding Amperes E = I x R Finding Voltage R= E / I Finding Resistance

  26. T5D Ohm’s Law T5D2THE FORMULA VOLTATE (E) EQUALS CURRENT (I) MULTIPLIED BY RESISTANCE (R) IS USED TO CALCULATE VOLTAGE IN A CIRCUIT E is for Voltage, I is for current, and R is for resistance The math is easy Two known numbers are given, solve for the unknown Cover up the unknown and plug the numbers in the other two E = I x R Finding Voltage I = E / R Finding Amperes R= E / I Finding Resistance

  27. T5D Ohm’s Law T5D3 THE FORMULA RESISTANCE (R) EQUALS VOLTAGE (E) DIVIDED BY CURRENT (I) IS USED TO CALCULATE RESISTANCE IN A CIRCUIT. E is for Voltage, I is for current, and R is for resistance The math is easy Two known numbers are given, solve for the unknown Cover up the unknown and plug the numbers in the other two E = I x R Finding Voltage R= E / I Finding Resistance I = E / R Finding Amperes

  28. T5D Ohm’s Law T5D4 The resistance of a circuit in which a current of 3 amperes flows through a resistor connected to 90 volts is 30 ohms. Solving for “R” so cover up the “R” and plug in the other two numbers E is given as 90 volts and I is given as 3 amperes R = E / I R = 90 / 3 R = 30 ohms

  29. T5D Ohm’s Law T5D5 The resistance in a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes is 8 ohms. Solving for “R” so cover up the “R” and plug in the other two numbers E is given as 12 volts and I is given as 1.5 amperes R = E / I R = 12 / 1.5 R = 8 ohms

  30. T5D Ohm’s Law T5D6The resistance of a circuit that draws 4 amperes from a 12-volt source is 3 ohms. Solving for “R” so cover up the “R” and plug in the other two numbers E is given as 12 volts and I is given as 4 amperes R = E / I R = 12 / 4 R = 3 ohms

  31. T5D Ohm’s Law T5D7 The current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms is 1.5 amperes. Solving for “I” so cover up the “I” and plug in the other two numbers E is given as 120 volts and R is given as 80 ohms I = E / R I = 120 / 80 I = 1.5 amperes

  32. T5D Ohm’s Law T5D8 The current flowing through a 100-ohm resistor connected across 200 volts is 2 amperes. Solving for “I” so cover up the “I” and plug in the other two numbers E is given as 200 volts and R is given as 100 ohms I = E / R I = 200 / 100 I = 2 amperes

  33. T5D Ohm’s Law T5D9 The current flowing through a 24-ohm resistor connected across 240 volts 10 amperes. Solving for “I” so cover up the “I” and plug in the other two numbers E is given as 240 volts and R is given as 24 ohms I = E / R I = 240 / 24 I = 10 amperes

  34. T5D Ohm’s Law T5D10 The voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it is 1 volt. Solving for “E” so cover up the “E” and plug in the other two numbers I is given as 0.5 amperes and R is given as 2 ohms E = I x R E = 0.5 x 2 E= 1 volt

  35. T5D Ohm’s Law T5D11The voltage across a 10-ohm resistor if a current of 1 amperes flows through it is 10 volts. Solving for “E” so cover up the “E” and plug in the other two numbers I is given as 1 ampere and R is given as 10 ohms E = I x R E = 1 x 10 E= 10 volts

  36. T5D Ohm’s Law T5D12The voltage across a 10-ohm resistor if a current of 2 amperes flows through it is 20 volts. Solving for “E” so cover up the “E” and plug in the other two numbers I is given as 1 ampere and R is given as 10 ohms E = I x R E = 2 x 10 E= 20 volts

  37. T5A07 Which of the following is a good electrical conductor? • Glass • Wood • Copper • Rubber

  38. T5A08 Which of the following is a good electrical insulator? • Copper • Glass • Aluminum • Mercury

  39. T5D01 What formula is used to calculate current in a circuit? • Current (I) equals voltage (E) multiplied by resistance (R) • Current (I) equals voltage (E) divided by resistance (R) • Current (I) equals voltage (E) added to resistance (R) • Current (I) equals voltage (E) minus resistance (R)

  40. T5D02 What formula is used to calculate voltage in a circuit? • Voltage (E) equals current (I) multiplied by resistance (R) • Voltage (E) equals current (I) divided by resistance (R) • Voltage (E) equals current (I) added to resistance (R) • Voltage (E) equals current (I) minus resistance (R)

  41. T5D03 What formula is used to calculate resistance in a circuit? • Resistance (R) equals voltage (E) multiplied by current (I) • Resistance (R) equals voltage (E) divided by current (I) • Resistance (R) equals voltage (E) added to current (I) • Resistance (R) equals voltage (E) minus current (I)

  42. T5D04 What is the resistance of a circuit in which a current of 3 amperes flows through a resistor connected to 90 volts? • 3 ohms • 30 ohms • 93 ohms • 270 ohms

  43. T5D05 What is the resistance in a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes? • 18 ohms • 0.125 ohms • 8 ohms • 13.5 ohms

  44. T5D06 What is the resistance of a circuit that draws 4 amperes from a 12-volt source? • 3 ohms • 16 ohms • 48 ohms • 8 ohms

  45. T5D07 What is the current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms? • 9600 amperes • 200 amperes • 0.667 amperes • 1.5 amperes

  46. T5D08 What is the current flowing through a 100-ohm resistor connected across 200 volts? • 20,000 amperes • 0.5 amperes • 2 amperes • 100 amperes

  47. T5D09 What is the current flowing through a 24-ohm resistor connected across 240 volts? • 24,000 amperes • 0.1 amperes • 10 amperes • 216 amperes

  48. T5D10 What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it? • 1 volt • 0.25 volts • 2.5 volts • 1.5 volts

  49. T5D11 What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it? • 1 volt • 10 volts • 11 volts • 9 volts

  50. T5D12 What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it? • 8 volts • 0.2 volts • 12 volts • 20 volts

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