# Electrical Theory for Troubleshooters

## Electrical Skills

### Course 1 – Ohm’s Law

**Prerequisites**: This lesson is designed so that no prior knowledge is required.

**Description**: This lesson shows and explains how a basic DC electrical circuit operates and how voltage, current, and resistance behave in a series circuit, a parallel circuit, and a series parallel circuit. Procedures for using Ohm’s Law to calculate voltage, current, and resistance in a circuit are also provided.

**Objectives**:

- Define electricity
- Describe how a simple electrical circuit operates
- Use Ohm’s Law to calculate voltage, current, and resistance in any kind of circuit

### Course 2 – AC Characteristics

**Prerequisites**: This lesson is designed for participants familiar with Ohm’s Law.

**Description**: This lesson covers the basic characteristics of AC circuits including the relationship between voltage and current flow in an AC circuit, the way in which AC voltage is induced, and the cause and effect of inductance and capacitance in AC circuits. The lesson shows and explains how to use a sine wave to interpret changes in AC voltage over time, how to determine the frequency of AC voltage, and how to recognize the effects of inductance and capacitance in AC circuits.

**Objectives**:

- State the basic operating characteristics of AC voltage
- Use a sine wave to determine the frequency of AC voltage
- Define the principles of magnetic attraction and repulsion
- Define lines of flux and flux density
- Describe how AC voltage is induced
- Describe how a capacitor operates in an AC circuit
- Describe how capacitance affects the relationship between voltage and current in an AC circuit
- Interpret AC voltage over time

### Course 3 – Three-phase AC Circuits

**Prerequisites**: This lesson is designed for participants familiar with AC circuits and AC voltage. A basic understanding of how to interpret changes in AC voltage over time is also required.

**Description**: This lesson shows how three-phase AC voltage is generated and describes different characteristics of three-phase voltage. The lesson introduces two types of winding electrical connections with graphic demonstrations of their effect on voltage and current. Also presented are transformers and the way in which they affect voltage and current.

**Objectives**:

- Explain how voltage is induced in a three-phase system
- Use a sine wave to explain how three-phase voltage changes over time
- Describe the effect of three- and four-wire wye connections have on the relationships between phase and line voltage and current in a three-phase system
- Describe the effect of a delta connection on the relationship between phase and line voltage and current in a three-phase system
- Identify the basic parts of a transformer and describe their functions
- Explain what determines how much voltage a transformer produces
- Describe how current changes from the primary winding to the secondary winding

### Course 4 – Semiconductors and Diodes

**Prerequisites**: This lesson is designed for participants familiar with AC/DC theory, electrical safety, electrical print reading, electrical connections, and the proper use of electrical test instruments.

**Description**: This lesson presents the physical and electrical properties of different semiconductor material types and how current flows through each type. The lesson shows codes and symbols for diodes and how to interpret schematic drawings and manufacturer’s markings on diodes. Operating characteristic curves and zener diodes are also explained.

**Objectives**:

- Describe the physical and electrical properties and current flow of N-type and P-type semiconductor material
- Understand the PN junction theory
- Describe the codes and symbols that are used to identify a diode
- Interpret schematic drawings and manufacturer’s markings for diodes
- Test an unmarked diode to identify the anode and cathode
- Explain how the operating characteristic curve represents diode operation in terms of the relationship between current and voltage
- Explain how the operating characteristic curve indicates forward operating current in an AC circuit
- Describe how zener diodes operate and how they are used to regulate voltage in a circuit

### Course 5 – Rectifiers and Filters

**Prerequisites**: This lesson is designed for participants familiar with AC/DC theory, electrical safety, electrical print reading, electrical connections, semiconductors and diodes. The ability to use electrical test instruments is also required.

**Description**: This lesson presents the basic operating theories of electronic power supplies, half-wave rectifiers, full-wave rectifiers, full-wave bridge rectifiers, capacitive input filters, and inductive input filters. The lesson shows how to calculate the expected DC output voltage for a half-wave rectifier, full-wave rectifier, and full-wave bridge rectifier.

**Objectives**:

- Identify and state the function of the major components in an electronic power supply
- Explain the operation of a half-wave rectifier circuit
- Calculate the expected DC output voltage and recognize the appropriate output waveform from a half-wave rectifier
- Explain the operation of a full-wave rectifier circuit
- Calculate the expected DC output voltage and recognize the output waveform from a full-wave bridge rectifier
- Explain the operation of capacitive and inductive input filters

### Course 6 – Power Devices

**Prerequisites**: This lesson is designed for participants familiar with AC/DC theory, electrical safety, electrical print reading, electrical connections, semiconductors and diodes. The ability to use electrical test instruments is also required.

**Description**: This lesson describes the operating principles and function of transistors, SCR’S, and triacs and shows how current flows through each device. Schematic symbols for transistors, SCR’S, and triacs are also shown and explained.

**Objectives**:

- Describe the switching and amplification functions as well as the three regions of a transistor
- Identify the schematic symbols for PNP and NPN transistors and explain how current flows through each type
- Explain how transistors perform switching and amplification functions
- Use an ohmmeter to test a transistor
- Identify the schematic symbols for a SCR and a triac and explain how they operate

### Course 7 – Introduction to Digital Devices

**Prerequisites**: This lesson is designed for participants familiar with basic electrical theory, electrical safety, electrical connections, electrical print reading, semiconductors, diodes, and the operating characteristics of transistors, resistors, and other basic circuit components. The ability to properly use electrical/electronic test instruments is also required.

**Description**: This lesson covers how digital electronic components process and transmit information, the principles of operation of basic logic gates, and how the binary number system can be used to represent information.

**Objectives**:

- Describe how digital electronic circuits process information
- Explain the logic functions that can be performed by digital electronic circuits
- Explain the truth tables associated with logic functions
- Determine the logic function that is performed by a circuit
- Explain an integrated circuit
- Explain how the binary number system is commonly used in digital electronic circuits