Basic Electricity Two Laws Technician License Course Module Three Radio and Electronics Fundamentals Basic Electricity Two Laws

Fundamentals of Electricity When dealing with electricity what we are referring to is the flow of electrons through a conductor Electrons are negatively charged atomic particles The opposite charge is the positive charge A conductor is a material that allows electrons to move with relative freedom within the material You need to take some time to make sure all the students are on the same page when dealing with electronics fundamentals. You will probably find a wide range of knowledge from those who have no clue what you’re talking about to those who know far more about the topic as you do. Acknowledge this right up front, but tell the students you are going to lay the vocabulary foundation for material that follows. For those with little knowledge, tell them to hang on because it will become clear as the lesson proceeds, for those more knowledgeable, tell them to be patient and allow for a little instructor license to over simplify so that all can understand. Point out that the opposite of a conductor is an insulator that does not allow for the free movement of electrons. As an aside, there are materials that under some conditions act as conductors and under other conditions act as insulators…these materials are semi-conductors, the basic materials of today’s solid state technology. 2

Fundamentals of Electricity In electronics and radio, we control the flow of electrons to make things happen You need to have a basic understanding of how and why we control the flow of electrons so that you can better operate your radio Use this time to provide some motivation of “why do I need to know this stuff.” 3

Conductors & Insulators Conductors allow electrons to flow Copper, silver, gold Insulators impede the flow of electrons Rubber, glass Use this time to provide some motivation of “why do I need to know this stuff.” 4

Basic Characteristics of Electricity There are three characteristics to electricity Voltage Current Resistance All three must be present for electrons to flow

Basic Characteristics of Electricity The flow of water through a hose is a good analogy to understand the three characteristics of electricity and how they are related Take some time to talk the students through the water analogy. Pressure that pushes water through a hose, in electricity is voltage (or Electromotive force). The water in the hose, in electricity is the electrons (current) that will move. The friction that prevents the water from just freely moving through the hose, in electricity is resistance. Resistance comes from the electrons running into obstacles within the conductor (and other electrons) as they pass through. Have the student rub their hands together and observe what happens (heat). When resistance impedes the flow of electronics (slows the flow down), the change in kinetic energy (energy of movement) must be turned into some form of energy (remember energy is neither created or destroyed, it is just turned into something else) in this case heat. 6

Characteristics of Electricity are Interelated Voltage, current, and resistance must be present to have current flow Just like water flowing through a hose, changes in voltage, current, and resistance affect each other That effect is mathematically expressed in Ohm’s Law If there is no push (voltage) there is no current (current by definition is flowing electrons), if there is no movement, there can be no resistance. If there is nothing to push, there will be no pressure, no movement-no resistance. There is always going to be some form of impediment to movement. What you are describing here is that inter-relationship which is Ohm’s law 7

E I R Ohm’s Law E is voltage I is current R is resistance R=E/I I=E/R Units-volts I is current Units-ampere R is resistance Units-ohms R=E/I I=E/R E=I x R E I R Go over the simple Ohm’s Law math and provide a few examples of how to solve problems. Give some homework problems that are the same as test questions (without telling them that they are test questions). Have the students solve these problems so they are confident that they can do the math 8

Moving Electrons Doing Something Useful Anytime energy is expended to do something - work is performed When moving electrons do some work, power is consumed Power is measured in the units of Watts Discuss the concept of power in electronics. Student will probably be familiar with this concept because of their electric bill. 9

Power Formula Power is defined as the amount of current that is being pushed through a conductor or device to do work P = I x E E = P/I I = P/E P Go through some simple problems using the power formula. Again use test question examples for homework. I E 10

Two Basic Kinds 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 Discuss the two different kinds of current and what they might be used for. Point out to the students that their household AC current is frequently converted into DC to run many household appliances. That conversion is done inside the appliance or inside an external converter like a wall-wart. Explain why house current is AC (easier to transmit the electricity from the power plant to the home) 11

VEC Question Pool Module Three

T5A01 Electrical current is measured in which of the following units? A. Volts B. Watts C. Ohms D. Amperes

T5A01 (D) Electrical current is measured in which of the following units? A. Volts B. Watts C. Ohms D. Amperes

T5A02 Electrical power is measured in which of the following units? A. Volts B. Watts C. Ohms D. Amperes

T5A02 (B) Electrical power is measured in which of the following units? A. Volts B. Watts C. Ohms D. Amperes

T5A03 What is the name for the flow of electrons in an electric circuit? A. Voltage B. Resistance C. Capacitance D. Current

T5A03 (D) What is the name for the flow of electrons in an electric circuit? A. Voltage B. Resistance C. Capacitance D. Current

T5A04 What is the name for a current that flows only in one direction? A. Alternating current B. Direct current C. Normal current D. Smooth current

T5A04 (B) What is the name for a current that flows only in one direction? A. Alternating current B. Direct current C. Normal current D. Smooth current

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

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

T5A06 How much voltage does a mobile transceiver usually require? A. About 12 volts B. About 30 volts C. About 120 volts D. About 240 volts

T5A06 (A) How much voltage does a mobile transceiver usually require? A. About 12 volts B. About 30 volts C. About 120 volts D. About 240 volts

T5A07 Which of the following is a good electrical conductor? A. Glass B. Wood C. Copper D. Rubber

T5A07 (C) Which of the following is a good electrical conductor? A. Glass B. Wood C. Copper D. Rubber

T5A08 Which of the following is a good electrical insulator? A. Copper B. Glass C. Aluminum D. Mercury

T5A08 (B) Which of the following is a good electrical insulator? A. Copper B. Glass C. Aluminum D. Mercury

T5A09 What is the name for a current that reverses direction on a regular basis? A. Alternating current B. Direct current C. Circular current D. Vertical current

T5A09 (A) What is the name for a current that reverses direction on a regular basis? A. Alternating current B. Direct current C. Circular current D. Vertical current

T5A10 Which term describes the rate at which electrical energy is used? A. Resistance B. Current C. Power D. Voltage

T5A10 (C) Which term describes the rate at which electrical energy is used? A. Resistance B. Current C. Power D. Voltage

T5A11 What is the basic unit of electromotive force? A. The volt B. The watt C. The ampere D. The ohm

T5A11 (A) What is the basic unit of electromotive force? A. The volt B. The watt C. The ampere D. The ohm

T5C08 What is the formula used to calculate electrical power in a DC circuit? A. Power (P) equals voltage (E) multiplied by current (I) B. Power (P) equals voltage (E) divided by current (I) C. Power (P) equals voltage (E) minus current (I) D. Power (P) equals voltage (E) plus current (I)

T5C08 (A) What is the formula used to calculate electrical power in a DC circuit? A. Power (P) equals voltage (E) multiplied by current (I) B. Power (P) equals voltage (E) divided by current (I) C. Power (P) equals voltage (E) minus current (I) D. Power (P) equals voltage (E) plus current (I)

T5C09 How much power is being used in a circuit when the applied voltage is 13.8 volts DC and the current is 10 amperes? A. 138 watts B. 0.7 watts C. 23.8 watts D. 3.8 watts

T5C09 (A) How much power is being used in a circuit when the applied voltage is 13.8 volts DC and the current is 10 amperes? A. 138 watts B. 0.7 watts C. 23.8 watts D. 3.8 watts

T5C10 How much power is being used in a circuit when the applied voltage is 12 volts DC and the current is 2.5 amperes? A. 4.8 watts B. 30 watts C. 14.5 watts D. 0.208 watts

T5C10 (B) How much power is being used in a circuit when the applied voltage is 12 volts DC and the current is 2.5 amperes? A. 4.8 watts B. 30 watts C. 14.5 watts D. 0.208 watts

T5C11 How many amperes are flowing in a circuit when the applied voltage is 12 volts DC and the load is 120 watts? A. 0.1 amperes B. 10 amperes C. 12 amperes D. 132 amperes

T5C11 (B) How many amperes are flowing in a circuit when the applied voltage is 12 volts DC and the load is 120 watts? A. 0.1 amperes B. 10 amperes C. 12 amperes D. 132 amperes

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

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

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

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

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

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

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

T5D04 (B) What is the resistance of a circuit in which a current of 3 amperes flows through a resistor connected to 90 volts? A. 3 ohms B. 30 ohms C. 93 ohms D. 270 ohms

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

T5D05 (C) What is the resistance in a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes? A. 18 ohms B. 0.125 ohms C. 8 ohms D. 13.5 ohms

T5D06 What is the resistance of a circuit that draws 4 amperes from a 12-volt source? A. 3 ohms B. 16 ohms C. 48 ohms D. 8 Ohms

T5D06 (A) What is the resistance of a circuit that draws 4 amperes from a 12-volt source? A. 3 ohms B. 16 ohms C. 48 ohms D. 8 Ohms

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

T5D07 (D) What is the current flow in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms? A. 9600 amperes B. 200 amperes C. 0.667 amperes D. 1.5 amperes

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

T5D08 (C) What is the current flowing through a 100- ohm resistor connected across 200 volts? A. 20,000 amperes B. 0.5 amperes C. 2 amperes D. 100 amperes

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

T5D09 (C) What is the current flowing through a 24- ohm resistor connected across 240 volts? A. 24,000 amperes B. 0.1 amperes C. 10 amperes D. 216 amperes

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

T5D10 (A) What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it? A. 1 volt B. 0.25 volts C. 2.5 volts D. 1.5 volts

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

T5D11 (B) What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it? A. 1 volt B. 10 volts C. 11 volts D. 9 volts

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

T5D12 (D) What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it? A. 8 volts B. 0.2 volts C. 12 volts D. 20 volts

End Module Three