Lesson 3: Introduction to Transformers
questions with correct answers 2025.
True or False: The current and the magnetic field in an AC circuit reverse direction twice
in each cycle. - ANSWER: True
This means that the north and south poles interchange twice in every cycle, or 120
times per second. in a 60 hertz system.
Ohm's Law cannot be used directly on AC circuits because ? .
a. of alternating current
b. of alternating voltage
c. of line loss and heat created by current flow
d. reactance and resistance oppose current flow - ANSWER: d. reactance and
resistance oppose current flow
In AC circuits, reactance (the opposition to the flow of current, due to induction and
capacitance) as well as resistance oppose current flow. The combination of reactance
and resistance is impedance (Z), and is also measured in ohms. Because of reactance,
Ohm's law cannot be used directly in alternating current.
True or False: Impedance is the combination of resistance and current. - ANSWER:
False
The combination of reactance and resistance is impedance (Z), and is also measured in
ohms.
All transformer connections, whether single or 3-phase, are based on the voltage and
current rules for ? and ? circuits.
a. AC / DC
b. resistance / reactance
c. series / parallel
d. transformers / resistance - ANSWER: c. series / parallel
, AC at 60 hertz per second increases and decreases in value ? times per second.
a. 60
b. 120
c. 180
d. 200 - ANSWER: b. 120
The current also reverses its direction 120 times per second
True or False: The magnetic field surrounding a coil rises and falls in unison with the
current. - ANSWER: True
In a 60 cycle system this occurs 120 times per second
True or False: As the magnetic field in the primary coil increases in strength, the current
in the secondary increases. - ANSWER: True
As the field in the primary coil increases in strength, the field increasingly cuts into the
turns of the secondary coil, making current in the secondary coil increase.
To obtain maximum induction, the coils must be ? and ? so the field is able to cut across
the conductors of the other.
a. parallel / at a right angle
b. parallel / sufficiently close
c. parallel / touching
d. the same size / at a right angle - ANSWER: b. parallel / sufficiently close
Lines of force surround an energized conductor throughout its length, but are highly
concentrated where the conductor is formed into a coil
The lines of force must be ? in order to induce a voltage and cause a current to flow in
the circuit.
a. expanding
b. in motion
c. sufficiently close
d. sufficiently strong - ANSWER: b. in motion
Movement of the lines of force or movement of the conductor is necessary in order to
induce a voltage into the conductor.
True or False: In order for current to flow, the conductor must be a closed circuit. -
ANSWER: True
When current flows through a conductor, a magnetic field is produced around the
conductor.
The ? concentrates and directs the magnetic field and makes transformers possible.
questions with correct answers 2025.
True or False: The current and the magnetic field in an AC circuit reverse direction twice
in each cycle. - ANSWER: True
This means that the north and south poles interchange twice in every cycle, or 120
times per second. in a 60 hertz system.
Ohm's Law cannot be used directly on AC circuits because ? .
a. of alternating current
b. of alternating voltage
c. of line loss and heat created by current flow
d. reactance and resistance oppose current flow - ANSWER: d. reactance and
resistance oppose current flow
In AC circuits, reactance (the opposition to the flow of current, due to induction and
capacitance) as well as resistance oppose current flow. The combination of reactance
and resistance is impedance (Z), and is also measured in ohms. Because of reactance,
Ohm's law cannot be used directly in alternating current.
True or False: Impedance is the combination of resistance and current. - ANSWER:
False
The combination of reactance and resistance is impedance (Z), and is also measured in
ohms.
All transformer connections, whether single or 3-phase, are based on the voltage and
current rules for ? and ? circuits.
a. AC / DC
b. resistance / reactance
c. series / parallel
d. transformers / resistance - ANSWER: c. series / parallel
, AC at 60 hertz per second increases and decreases in value ? times per second.
a. 60
b. 120
c. 180
d. 200 - ANSWER: b. 120
The current also reverses its direction 120 times per second
True or False: The magnetic field surrounding a coil rises and falls in unison with the
current. - ANSWER: True
In a 60 cycle system this occurs 120 times per second
True or False: As the magnetic field in the primary coil increases in strength, the current
in the secondary increases. - ANSWER: True
As the field in the primary coil increases in strength, the field increasingly cuts into the
turns of the secondary coil, making current in the secondary coil increase.
To obtain maximum induction, the coils must be ? and ? so the field is able to cut across
the conductors of the other.
a. parallel / at a right angle
b. parallel / sufficiently close
c. parallel / touching
d. the same size / at a right angle - ANSWER: b. parallel / sufficiently close
Lines of force surround an energized conductor throughout its length, but are highly
concentrated where the conductor is formed into a coil
The lines of force must be ? in order to induce a voltage and cause a current to flow in
the circuit.
a. expanding
b. in motion
c. sufficiently close
d. sufficiently strong - ANSWER: b. in motion
Movement of the lines of force or movement of the conductor is necessary in order to
induce a voltage into the conductor.
True or False: In order for current to flow, the conductor must be a closed circuit. -
ANSWER: True
When current flows through a conductor, a magnetic field is produced around the
conductor.
The ? concentrates and directs the magnetic field and makes transformers possible.
