PT3: Introduction to Electrical Circuits

Electrical

Module 26103-23

Introduction to Electrical Circuits

Copyright © 2024 by NCCER, Alachua, FL 32615. Published by Pearson. All rights reserved.

1.0.0 Atomic Structure and Electricity

Module 26103-23 – Introduction to Electrical Circuits

Objective

1. Describe atomic structure as it relates to electricity.

a. Identify the parts of an atom.

b. Compare the atomic structures of conductors and insulators.

c. Identify the role of magnetism in electrical devices.

Module 26103-23 – Introduction to Electrical Circuits

Performance Tasks

There are no Performance Tasks associated with this section.

Module 26103-23 – Introduction to Electrical Circuits

1.0.0–1.1.0 Examining the Components of an Atom

•

Atoms contain the following
subatomic particles:
–

Proton
–

Electron
–

Neutron

•

Protons and neutrons are in the
nucleus.

•

Electrons orbit the nucleus in a
shell.

Module 26103-23 – Introduction to Electrical Circuits

1.1.1 Valence Shell

The outer shell of an atom is the valence
shell.
•

A valence shell with fewer
electrons will likely lose electrons.
•

A valence shell with more
electrons will likely gain electrons.

Module 26103-23 – Introduction to Electrical Circuits

1.1.2 Ions

Ions are atoms that gain or lose
electrons.
•

Atoms that gain electrons are
negative ions.
•

Atoms that lose electrons are
positive ions.

Module 26103-23 – Introduction to Electrical Circuits

1.2.0 Atomic Structures of Conductors and Insulators

•

Conductor
–

Three or fewer valence electrons
–

Easily transfers electrons

•

Insulator
–

Five or more valence electrons
–

Prevents the flow of electrons

•

Semiconductor
–

Four valence electrons
–

Can be either a conductor or insulator

Module 26103-23 – Introduction to Electrical Circuits

1.3.0 Magnetism in Electrical Devices

•

The poles of a magnet repel one
another, creating a magnetic field.

•

Electrical current also produces
magnetism.
–

A conductor coiled around an
iron bar creates a strong
electromagnet.

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (1 of 4)

Atom: The smallest particle to which an element may be divided and still
retain the properties of that element.

Battery: A direct current (DC) voltage source consisting of two or more cells
that convert chemical energy into electrical energy.

Charge: A quantity of electricity that is either positive or negative.

Circuit: A complete path for current flow.

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (2 of 4)

Conductor: A material through which it is relatively easy to maintain an
electric current.

Electron: A negatively charged particle that orbits the nucleus of an atom.

Insulator: A material through which it is difficult to conduct an electric
current.

Ion: An atom with a negative or positive charge due to gaining or losing
electrons.

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (3 of 4)

Neutron: An electrically neutral particle (neither positive nor negative) that
has the same mass as a proton and is found in the nucleus of an atom.

Nucleus: The center of an atom. It contains the protons and neutrons of the
atom.

Proton: The smallest positively charged particle of an atom. Protons are
contained in the nucleus of an atom.

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (4 of 4)

Semiconductor: A material that has electrical properties between that of a
conductor and an insulator. Semiconductors are used to control current flow
in electronic equipment and other applications, such as solar photovoltaic
systems.

Valence shell: The outermost ring of electrons that orbit the nucleus of an
atom.

Module 26103-23 – Introduction to Electrical Circuits

1.0.0 Section Review Question 1

1. A proton repels a(n) _____.

a. electron

b. proton

c. neutron

d. negative ion

Module 26103-23 – Introduction to Electrical Circuits

1.0.0 Section Review Question 1 Answer

1. A proton repels a(n) _____.

a. electron

b. proton

c. neutron

d. negative ion

Module 26103-23 – Introduction to Electrical Circuits

1.0.0 Section Review Question 2

2. An atom with seven valence electrons is most likely a(n) _____.

a. insulator

b. conductor

c. capacitor

d. semiconductor

Module 26103-23 – Introduction to Electrical Circuits

1.0.0 Section Review Question 2 Answer

2. An atom with seven valence electrons is most likely a(n) _____.

a. insulator

b. conductor

c. capacitor

d. semiconductor

Module 26103-23 – Introduction to Electrical Circuits

1.0.0 Section Review Question 3

3. Current flowing through a conductor coiled around an iron bar produces
a(n) _____.

a. insulator

b. capacitor

c. electromagnet

d. turbine

Module 26103-23 – Introduction to Electrical Circuits

1.0.0 Section Review Question 3 Answer

3. Current flowing through a conductor coiled around an iron bar produces
a(n) _____.

a. insulator

b. capacitor

c. electromagnet

d. turbine

Next…

2.0.0
Electrical Calculations

Read Sections 2.0.0 through 2.3.2. Complete the 2.0.0 Section
Review.

Electrical

Module 26103-23

Introduction to Electrical Circuits

Copyright © 2024 by NCCER, Alachua, FL 32615. Published by Pearson. All rights reserved.

2.0.0 Electrical Calculations

Module 26103-23 – Introduction to Electrical Circuits

Objective

2. Use equations to determine circuit values.

a. Define various circuit values.

b. Explain how to use Ohm’s law to solve for unknown circuit values.

c. Explain how to calculate electrical power.

Module 26103-23 – Introduction to Electrical Circuits

Performance Tasks

There are no Performance Tasks associated with this section.

Module 26103-23 – Introduction to Electrical Circuits

2.0.0–2.1.0 Electrical Calculations (1 of 2)

•

Voltage is the driving force that makes current flow in a circuit, often
represented by the letter E.

•

Current is the movement, or flow, of electrons in a circuit. Current or
intensity of flow (I) is measured in amperes (A).

•

Resistance is an electrical property that opposes the flow of current
through a circuit. Resistance is represented by the letter R and is
measured in ohms (Ω).

•

Power is the rate of doing work, or the rate at which energy is used or
dissipated. Electrical power is measured in watts (W).

Module 26103-23 – Introduction to Electrical Circuits

2.0.0–2.1.0 Electrical Calculations (2 of 2)

A basic electrical circuit has a voltage
source, a load, conductors, and a
switch.

Module 26103-23 – Introduction to Electrical Circuits

2.1.1 Voltage

•

Voltage is measured in volts.

•

One volt is the electromotive
force needed to push one
ampere of current through a
resistance of one ohm.

Module 26103-23 – Introduction to Electrical Circuits

2.1.2 Current

Current is the flow of electrons
along a conductor.
•

Measured in amps
•

Represented with the
letter I in equations

Module 26103-23 – Introduction to Electrical Circuits

2.1.3 Resistance

•

Resistance is the opposition
to current flow.
–

Measured in ohms
–

Represented by the
symbol R in equations

•

A resistor has a known,
specified resistance.

Module 26103-23 – Introduction to Electrical Circuits

2.2.0 Calculating Circuit Values Using Ohm’s Law

•

Ohm’s law states that the current in a circuit is directly proportional to the
voltage and inversely proportional to the resistance.

•

If both voltage and resistance are known, you can solve for current:

Current 𝐼 =
Voltage (𝐸)
Resistance (𝑅)

Module 26103-23 – Introduction to Electrical Circuits

2.2.1–2.2.2 Rearranging Ohm’s Law

•

When current and resistance are
known, you can solve for voltage:

𝐸 = 𝐼 × 𝑅

•

When voltage and current are known,
you can solve for resistance.

𝑅 = 𝐸
𝐼

Module 26103-23 – Introduction to Electrical Circuits

2.3.0 Calculating Electrical Power

•

Power is the rate of doing work
and is measured in watts (W).

Watts = volts × amperes

•

A kilowatt (kW) is 1,000 watts.

•

A megawatt (MW) is 1 million
watts.

Module 26103-23 – Introduction to Electrical Circuits

2.3.1 Power Equation

•

When you know current and
voltage, you can find the power in
watts.

•

Similar to Ohm’s law, it can be
rearranged to find current and
voltage.

Module 26103-23 – Introduction to Electrical Circuits

2.3.2 Power Rating of Resistors

•

Too much current flowing through a resistor will generate heat that can
damage or destroy the resistor.

•

Resistors have a power rating to show the maximum current it can carry.

•

Maximum current can be calculated with the follow formula:

𝐼 =

𝑃/𝑅

I = current in amperes

P = power in watts

R = resistance

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (1 of 5)

Ampere (A): The basic unit of measurement for electrical current,
represented by the letter A.

Coulomb (C): A unit of electrical charge equal to 6.24 × 1018 electrons (or
6.24 quintillion electrons). A coulomb is the common unit of quantity used for
specifying the size of a given charge.

Current: The movement, or flow, of electrons in a circuit. Current or intensity
of flow (I) is measured in amperes (A).

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (2 of 5)

Joule (J): A unit of energy measurement for doing work, represented by the
letter J. One joule is equal to one newton-meter (Nm).

Kilo: A prefix used to indicate one thousand; for example, one kilowatt is
equal to one thousand watts.

Mega: A prefix used to indicate one million; for example, one megawatt is
equal to one million watts.

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (3 of 5)

Ohm (Ω): The basic unit of measurement for resistance, represented by the
symbol Ω.

Ohm’s law: A rule stating that the current in a circuit is directly proportional
to the voltage and inversely proportional to the resistance. Stated
mathematically as current (I) equals voltage (E) divided by resistance (R).

Power: The rate of doing work, or the rate at which energy is used or
dissipated. Electrical power is measured in watts (W).

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (4 of 5)

Resistance: An electrical property that opposes the flow of current through a
circuit. Resistance is represented by the letter R and is measured in ohms
(Ω).

Resistor: A device in a circuit that restricts or opposes the flow of electrons.

Volt (V): The unit of measurement for voltage, represented by the letter V.
One volt is the electromotive force needed to push one ampere of current
through a resistance of one ohm.

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (5 of 5)

Voltage: The driving force that makes current flow in a circuit. Voltage, often
represented by the letter E, is also referred to as electromotive force (emf),
potential difference, or electrical pressure.

Watt (W): The basic unit of measurement for electrical power, represented by
the letter W.

Module 26103-23 – Introduction to Electrical Circuits

2.0.0 Section Review Question 1

1. Which of the following does not affect wire resistance?

a. Wire size

b. Type of power

c. Wire length

d. Material

Module 26103-23 – Introduction to Electrical Circuits

2.0.0 Section Review Question 1 Answer

1. Which of the following does not affect wire resistance?

a. Wire size

b. Type of power

c. Wire length

d. Material

Module 26103-23 – Introduction to Electrical Circuits

2.0.0 Section Review Question 2

2. Find the applied voltage when the current is 30A and the resistance is 4Ω.

a. 30V

b. 60V

c. 120V

d. 180V

Module 26103-23 – Introduction to Electrical Circuits

2.0.0 Section Review Question 2 Answer

2. Find the applied voltage when the current is 30A and the resistance is 4Ω.

a. 30V

b. 60V

c. 120V

d. 180V

Module 26103-23 – Introduction to Electrical Circuits

2.0.0 Section Review Question 3

3. Calculate the power in a circuit where the source of 240V produces 10A.

a. 12W

b. 240W

c. 1,200W

d. 2,400W

Module 26103-23 – Introduction to Electrical Circuits

2.0.0 Section Review Question 3 Answer

3. Calculate the power in a circuit where the source of 240V produces 10A.

a. 12W

b. 240W

c. 1,200W

d. 2,400W

Next…

3.0.0
Reading Schematic Diagrams

Read Sections 3.0.0 through 3.3.3. Complete the 3.0.0 Section
Review.

Electrical

Module 26103-23

Introduction to Electrical Circuits

Copyright © 2024 by NCCER, Alachua, FL 32615. Published by Pearson. All rights reserved.

3.0.0 Reading Schematic Diagrams

Module 26103-23 – Introduction to Electrical Circuits

Objective

3. Read simple schematic diagrams.

a. Identify the symbol for a resistor and determine its value based on
color codes.

b. Distinguish between series and parallel circuits.

c. Identify the instruments used to measure circuit values.

Module 26103-23 – Introduction to Electrical Circuits

Performance Tasks

There are no Performance Tasks associated with this section.

Module 26103-23 – Introduction to Electrical Circuits

3.0.0–3.1.0 Reading Schematic Diagrams (1 of 2)

•

In schematic diagrams, symbols
are used to represent the
components of a circuit.

•

Standard graphic symbols are
used for common electrical and
electronic components.

Module 26103-23 – Introduction to Electrical Circuits

3.0.0–3.1.0 Reading Schematic Diagrams (2 of 2)

•

The two most common types of
resisters are:
–

Wire-wound
–

Carbon composition

•

Most resistors are fixed with
standard values.

•

For small carbon composition
resistors, they are printed with a
color code to identify the
resistance value and tolerance.

Module 26103-23 – Introduction to Electrical Circuits

3.2.0 Series versus Parallel Circuits

•

A series circuit is a circuit with only one path for current flow.

•

A parallel circuit is a circuit in which each load is connected directly to the
voltage source.

Module 26103-23 – Introduction to Electrical Circuits

3.2.1 Working with Series Circuits

•

The total resistance of a series circuit
equals the sum of the individual
resistances.

Total resistance 𝑅! = 𝑅" + 𝑅#

•

Voltage drop is measured across a load
and depends on the resistance.

𝐸 = 𝐼 × 𝑅

Module 26103-23 – Introduction to Electrical Circuits

3.2.2 Working with Parallel Circuits (1 of 2)

•

In parallel circuits, each load is
connected directly to the voltage source.

•

Parallel circuits are the most common
way to wire circuits.

•

First, calculate total current:

𝐼 = 𝐸
𝑅
•

Then, calculate total resistance:

𝑅 = 𝐸
𝐼

Module 26103-23 – Introduction to Electrical Circuits

3.2.2 Working with Parallel Circuits (2 of 2)

•

For two resistances:
𝑅! = 𝑅"× 𝑅#
𝑅" + 𝑅#

•

For three or more resistances:

𝑅! =
1

1
𝑅"+ 1
𝑅#+ 1
𝑅$

•

For any number of equal resistances:

𝑅! = resistance of one resistor
total number of resistors

Module 26103-23 – Introduction to Electrical Circuits

3.2.3 Working with Series-Parallel Circuits

•

Loads are rarely connected in a
series-parallel circuit.

•

Parallel loads are first converted
to their equivalent series
resistances.

•

Then load resistances are added
to find the total resistance.

Module 26103-23 – Introduction to Electrical Circuits

3.2.4 Identifying Circuits

•

Loads are rarely
connected in series or in
series-parallel.

•

This circuit has only two
loads and is a parallel
circuit.

Module 26103-23 – Introduction to Electrical Circuits

3.3.0 Electrical Meters

•

The most common test meter is
volt-ohm-milliammeter (VOM) or
multimeter.

•

Used to measure:
–

AC and DC voltage
–

DC current
–

Resistance

Module 26103-23 – Introduction to Electrical Circuits

3.3.1 Measuring Current

•

For larger currents, a clamp-on
ammeter is used.

•

Always wear all required PPE
when using any meter.

•

Handle meters carefully to avoid
damage.

•

For analog meters, start at the
highest range and work down.

Module 26103-23 – Introduction to Electrical Circuits

3.3.2 Measuring Voltage

•

A voltmeter determines if the
correct voltage is available.

•

It is connected in parallel with the
circuit to be tested.

Module 26103-23 – Introduction to Electrical Circuits

3.3.3 Measuring Resistance

•

Make resistance measurement
with the system power off.

•

The ohmmeter has an internal
battery as a voltage source.
–

Measures resistance in a load
–

Measures continuity

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (1 of 3)

Ammeter: An instrument for measuring electrical current.

Ohmmeter: An instrument for measuring resistance.

Parallel circuit: A circuit in which each load is connected directly to the
voltage source; therefore, the voltage drop through each of the loads is the
same, and the current is divided between the loads.

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (2 of 3)

Schematic diagram: A type of drawing in which symbols are used to
represent the components in a system. Also referred to simply as a
schematic.

Series circuit: A circuit with only one path for current flow.

Module 26103-23 – Introduction to Electrical Circuits

Trade Terms (3 of 3)

Voltage drop: The change in voltage across a component that is caused by
the current flowing through it and the amount of resistance opposing it.

Voltmeter: An instrument for measuring voltage. The resistance of a
voltmeter is fixed. When a voltmeter is connected to a circuit, the current
passing through the meter will be directly proportional to the voltage at the
connection points.

Module 26103-23 – Introduction to Electrical Circuits

3.0.0 Section Review Question 1

1. A resistor with a gold band in the fourth position has a tolerance of _____.

a. ±1%

b. ±5%

c. ±10%

d. ±20%

Module 26103-23 – Introduction to Electrical Circuits

3.0.0 Section Review Question 1 Answer

1. A resistor with a gold band in the fourth position has a tolerance of _____.

a. ±1%

b. ±5%

c. ±10%

d. ±20%

Module 26103-23 – Introduction to Electrical Circuits

3.0.0 Section Review Question 2

2. The total resistance in a 120V series circuit with three 10Ω resistors is
_____.

a. 1.2Ω

b. 12Ω

c. 30Ω

d. 120Ω

Module 26103-23 – Introduction to Electrical Circuits

3.0.0 Section Review Question 2 Answer

2. The total resistance in a 120V series circuit with three 10Ω resistors is
_____.

a. 1.2Ω

b. 12Ω

c. 30Ω

d. 120Ω

Module 26103-23 – Introduction to Electrical Circuits

3.0.0 Section Review Question 3

3. Which of the following is true regarding the use of a clamp-on ammeter?

a. Place the jaws around a single conductor at a time.

b. Place the jaws around an even number of conductors only.

c. Start at the lowest meter range and work up.

d. Misaligned meter jaws can be corrected by tapping them with a
hammer.

Module 26103-23 – Introduction to Electrical Circuits

3.0.0 Section Review Question 3 Answer

3. Which of the following is true regarding the use of a clamp-on ammeter?

a. Place the jaws around a single conductor at a time.

b. Place the jaws around an even number of conductors only.

c. Start at the lowest meter range and work up.

d. Misaligned meter jaws can be corrected by tapping them with a
hammer.

Next…

Review for Module Testing

Complete the Review Questions at the end of the module and prepare
for the Module Test.