NCCER 26404 BASIC ELECTRICAL THEORY EXAM – QUESTIONS AND ANSWERS | VERIFIED AND WELL DETAILED
ANSWERS | PLUS RATIONALES | GUARANTEED PASS | LATEST EXAM UPDATE
Core Domains
Fundamentals of Electricity
Ohm’s Law and Electrical Calculations
Series and Parallel Circuits
Semiconductor Theory and Devices
Electrical Measuring Instruments
Alternating Current (AC) Theory
Transformers and Power Distribution
National Electrical Code (NEC) Basics
Motor Theory and Applications
Electrical Safety and Lockout/Tagout
Introduction
The NCCER 26404 Basic Electrical Theory Exam is a comprehensive assessment designed to validate a candidate’s
foundational knowledge of electrical principles and their practical application within the construction and industrial
trades. This examination evaluates understanding of core concepts such as Ohm’s Law, circuit calculations, and the
behavior of various electrical components, including semiconductors. The assessment emphasizes not only theoretical
recall but also the application of knowledge to real-world troubleshooting and decision-making scenarios. A significant
portion of the test is dedicated to ensuring candidates can safely and effectively interpret electrical schematics and
apply basic electrical laws to solve practical problems on the job site.
Question 1
What is the fundamental difference between a conductor and an insulator in terms of electron behavior?
A. Conductors have tightly bound electrons; insulators have free electrons.
,B. Conductors have free electrons in their valence shell; insulators have tightly bound electrons.
C. Conductors have more protons than electrons; insulators have fewer protons.
D. Conductors resist the flow of current; insulators allow the flow of current.
🟢 Correct Answer: B. Conductors have free electrons in their valence shell; insulators have tightly bound electrons.
🔴 Explanation: Conductors, like copper, have atoms with loosely bound electrons in their outer shell that can easily
move to create an electric current. Insulators, like rubber, have tightly bound electrons that resist this movement.
Question 2
If a circuit has a resistance of 10 ohms and a voltage of 120 volts, what is the current flowing through the circuit?
A. 1200 amperes
B. 120 amperes
C. 12 amperes
D. 0.083 amperes
🟢 Correct Answer: C. 12 amperes
🔴 Explanation: Ohm’s Law states I = V/R. I = 120V / 10Ω = 12 amperes.
Question 3
An SCR is made from adjoining layers of semiconductor material in which of the following arrangements?
A. PNPN
B. NPNP
C. NPN
D. PNP
🟢 Correct Answer: A. PNPN
🔴 Explanation: A Silicon-Controlled Rectifier (SCR) is a four-layer solid-state device composed of alternating layers
of P-type and N-type material, arranged as PNPN .
Question 4
In the figure of a transistor, if the lead marked 'A' is the emitter, what is its primary function in a transistor circuit?
,A. To emit charge carriers into the base.
B. To collect charge carriers from the base.
C. To control the flow of current between the other two terminals.
D. To amplify the voltage signal from the base.
🟢 Correct Answer: A. To emit charge carriers into the base.
🔴 Explanation: The emitter is heavily doped and has the primary function of emitting or supplying a large number
of charge carriers (electrons or holes) into the base region .
Question 5
AC power can be converted to DC power using which of the following devices?
A. A transformer
B. A rectifier diode
C. An inductor
D. A capacitor
🟢 Correct Answer: B. A rectifier diode
🔴 Explanation: A rectifier diode allows current to flow in one direction only, effectively converting alternating
current (AC) into a pulsating direct current (DC) .
Question 6
A transistor is made by joining how many layers of semiconductor material?
A. One
B. Two
C. Three
D. Four
🟢 Correct Answer: C. Three
🔴 Explanation: A bipolar junction transistor (BJT) is a three-layer semiconductor device, constructed as either an
NPN or PNP sandwich .
, Question 7
What is the definition of electrical power?
A. The opposition to the flow of current.
B. The rate at which electrical energy is transferred by an electric circuit.
C. The force that causes current to flow.
D. The total amount of current in a circuit.
🟢 Correct Answer: B. The rate at which electrical energy is transferred by an electric circuit.
🔴 Explanation: Electrical power is measured in watts and is calculated as the product of voltage and current. It
represents the amount of work done or energy consumed per unit of time.
Question 8
An electric motor works on the principle of the attracting and repelling forces of what?
A. Electric charges
B. Magnetic fields
C. Gravitational fields
D. Thermal expansion
🟢 Correct Answer: B. Magnetic fields
🔴 Explanation: An electric motor converts electrical energy into mechanical energy by using the interaction of
magnetic fields. The magnetic field of the stator and rotor attract and repel each other, producing torque.
Question 9
Silicon is widely used as a semiconductor primarily because it:
A. Has an extremely low resistance.
B. Is the best conductor of heat.
C. Can withstand heat and is abundant.
D. Allows current to flow only in one direction.
🟢 Correct Answer: C. Can withstand heat and is abundant.
ANSWERS | PLUS RATIONALES | GUARANTEED PASS | LATEST EXAM UPDATE
Core Domains
Fundamentals of Electricity
Ohm’s Law and Electrical Calculations
Series and Parallel Circuits
Semiconductor Theory and Devices
Electrical Measuring Instruments
Alternating Current (AC) Theory
Transformers and Power Distribution
National Electrical Code (NEC) Basics
Motor Theory and Applications
Electrical Safety and Lockout/Tagout
Introduction
The NCCER 26404 Basic Electrical Theory Exam is a comprehensive assessment designed to validate a candidate’s
foundational knowledge of electrical principles and their practical application within the construction and industrial
trades. This examination evaluates understanding of core concepts such as Ohm’s Law, circuit calculations, and the
behavior of various electrical components, including semiconductors. The assessment emphasizes not only theoretical
recall but also the application of knowledge to real-world troubleshooting and decision-making scenarios. A significant
portion of the test is dedicated to ensuring candidates can safely and effectively interpret electrical schematics and
apply basic electrical laws to solve practical problems on the job site.
Question 1
What is the fundamental difference between a conductor and an insulator in terms of electron behavior?
A. Conductors have tightly bound electrons; insulators have free electrons.
,B. Conductors have free electrons in their valence shell; insulators have tightly bound electrons.
C. Conductors have more protons than electrons; insulators have fewer protons.
D. Conductors resist the flow of current; insulators allow the flow of current.
🟢 Correct Answer: B. Conductors have free electrons in their valence shell; insulators have tightly bound electrons.
🔴 Explanation: Conductors, like copper, have atoms with loosely bound electrons in their outer shell that can easily
move to create an electric current. Insulators, like rubber, have tightly bound electrons that resist this movement.
Question 2
If a circuit has a resistance of 10 ohms and a voltage of 120 volts, what is the current flowing through the circuit?
A. 1200 amperes
B. 120 amperes
C. 12 amperes
D. 0.083 amperes
🟢 Correct Answer: C. 12 amperes
🔴 Explanation: Ohm’s Law states I = V/R. I = 120V / 10Ω = 12 amperes.
Question 3
An SCR is made from adjoining layers of semiconductor material in which of the following arrangements?
A. PNPN
B. NPNP
C. NPN
D. PNP
🟢 Correct Answer: A. PNPN
🔴 Explanation: A Silicon-Controlled Rectifier (SCR) is a four-layer solid-state device composed of alternating layers
of P-type and N-type material, arranged as PNPN .
Question 4
In the figure of a transistor, if the lead marked 'A' is the emitter, what is its primary function in a transistor circuit?
,A. To emit charge carriers into the base.
B. To collect charge carriers from the base.
C. To control the flow of current between the other two terminals.
D. To amplify the voltage signal from the base.
🟢 Correct Answer: A. To emit charge carriers into the base.
🔴 Explanation: The emitter is heavily doped and has the primary function of emitting or supplying a large number
of charge carriers (electrons or holes) into the base region .
Question 5
AC power can be converted to DC power using which of the following devices?
A. A transformer
B. A rectifier diode
C. An inductor
D. A capacitor
🟢 Correct Answer: B. A rectifier diode
🔴 Explanation: A rectifier diode allows current to flow in one direction only, effectively converting alternating
current (AC) into a pulsating direct current (DC) .
Question 6
A transistor is made by joining how many layers of semiconductor material?
A. One
B. Two
C. Three
D. Four
🟢 Correct Answer: C. Three
🔴 Explanation: A bipolar junction transistor (BJT) is a three-layer semiconductor device, constructed as either an
NPN or PNP sandwich .
, Question 7
What is the definition of electrical power?
A. The opposition to the flow of current.
B. The rate at which electrical energy is transferred by an electric circuit.
C. The force that causes current to flow.
D. The total amount of current in a circuit.
🟢 Correct Answer: B. The rate at which electrical energy is transferred by an electric circuit.
🔴 Explanation: Electrical power is measured in watts and is calculated as the product of voltage and current. It
represents the amount of work done or energy consumed per unit of time.
Question 8
An electric motor works on the principle of the attracting and repelling forces of what?
A. Electric charges
B. Magnetic fields
C. Gravitational fields
D. Thermal expansion
🟢 Correct Answer: B. Magnetic fields
🔴 Explanation: An electric motor converts electrical energy into mechanical energy by using the interaction of
magnetic fields. The magnetic field of the stator and rotor attract and repel each other, producing torque.
Question 9
Silicon is widely used as a semiconductor primarily because it:
A. Has an extremely low resistance.
B. Is the best conductor of heat.
C. Can withstand heat and is abundant.
D. Allows current to flow only in one direction.
🟢 Correct Answer: C. Can withstand heat and is abundant.
