Question 1

?   is used to convert electrical energy to a rotating mechanical force on a motor’s shaft

Accepted Answer

a. Electromagnetism

Question 2

true or false
Permanent magnets are used more often than electromagnets in motors, transformers, and solenoids.

Accepted Answer

False
The advantage of electromagnets is that they can be made stronger than permanent magnets and that magnetic strength can be easily controlled by regulating the electric current.

Question 3

Magnetic flux is densest and magnetic force is strongest at the   ?   of a magnet.

Accepted Answer

poles

Question 4

A   ?   is surrounded by a magnetic field that enters the south and exits the north pole.

Accepted Answer

bar magnet

Question 5

The molecular theory of magnetism states that   ?   materials are made up of a very large number of molecular domains that can be arranged in either a disorganized or organized manner.

Accepted Answer

ferromagnetic

Question 6

The relative permeability of air is   ?  .

Accepted Answer

1.0000004

Question 7

A(n)   ?   material is a material that can be very weakly magnetized in the opposite direction when a magnetic field is applied.

Accepted Answer

diamagnetic

Question 8

true or false
Electromagnetism is a permanent magnetic force.

Accepted Answer

False 
 Electromagnetism is a temporary magnetic force because the magnetic field is present only as long as current flows.

Question 9

true or false
Permanent magnets may be demagnetized by high temperatures.

Accepted Answer

true

Question 10

For an electromagnet, a more permeable core strengthens the   ?

Accepted Answer

concentration of magnetic flux

Question 11

?   is the condition where substantially all the magnetic domains in a magnetic core are aligned with the field and any increases in current no longer result in a stronger electromagnet.

Accepted Answer

Saturation

Question 12

true or false
With DC, both the current and magnetic field applied to a conductor start at zero and increase almost instantly to maximum value when a switch is closed; both drop to zero when the switch is opened.

Accepted Answer

True

Question 13

Every time the current passes the   ?   point of the AC sine wave, the direction of current flow and polarity of the magnetic field change.

Accepted Answer

zero

Question 14

The theory that current flows from the negative terminal to the positive terminal is called   ?   current flow.

Accepted Answer

electron

Question 15

The requirements for induction are:   ?  , a magnetic field, and relative motion between the conductor and the magnetic field.

Accepted Answer

a conductor

Question 16

?   in a circuit generates inductive reactance (XL), which is a counter voltage that opposes the source and resists change in the current flow.

Accepted Answer

Self-induction

Question 17

The   ?   rule is an explanation of the direction of a magnetic field around a coil relative to the direction of the current in the coil, where a left hand is used to illustrate the relationship.

Accepted Answer

left-hand coil

Question 18

true or false
The left-hand conductor rule describes the direction of a magnetic field around a conductor relative to the direction of the current in the conductor.

Accepted Answer

true

Question 19

t/f right-hand coil rule is an explanation of the relationship between the direction of the applied current in a conductor, the direction of the magnetic field around the conductor, and the direction of the induced motion of the conductor within a motor.

Accepted Answer

false

Question 20

?   is the ability of an inductor (coil) in one circuit to induce a voltage in another circuit or conductor.

Accepted Answer

Mutual induction

Question 21

With a DC motor, a   ?   is used to reverse the current direction, which keeps the current flowing in one direction (DC) through the windings to keep the polarity correct in order to interact with the main fields.

Accepted Answer

commutator
When this machine is used as a generator, the commutator provides the current flow in one direction to the load.

Question 22

?   law states that the polarity of induced voltage is such that it produces a current whose magnetic field opposes the change that produced it.

Accepted Answer

Lenz's

Question 23

The ability of a material to conduct magnetic flux is its   ?

Accepted Answer

permeability

Question 24

Mutual induction is the ability of an inductor (coil) in one circuit to   ?   a voltage in another circuit or conductor.

Accepted Answer

induce

Question 25

true or false
In the illustration, current flow is positive to negative. This means the illustration shows electron current flow.

Accepted Answer

false
conventional current flow is current flow from positive to negative.  Electron current flow is current flow from negative to positive.

Question 26

In the illustration, a magnetic field in the primary induces a voltage in the secondary. This means that the illustration shows   ?   induction.

Accepted Answer

mutual

Question 27

true or false
To maintain continuous rotation in an AC motor, a commutator is used to reverse the direction of the current.

Accepted Answer

false
A commutator is used to reverse the direction of the current in a DC motor. With an AC motor, the current automatically reverses direction because of the alternating current source.

Question 28

What is the approximate operating time for a Size-1 motor starter?

Accepted Answer

26 ms

Question 29

The ability of a material to retain residual magnetism is called   ?  .

Accepted Answer

permanence

Question	Answer
? is used to convert electrical energy to a rotating mechanical force on a motor’s shaft	a. Electromagnetism
true or false Permanent magnets are used more often than electromagnets in motors, transformers, and solenoids.	False The advantage of electromagnets is that they can be made stronger than permanent magnets and that magnetic strength can be easily controlled by regulating the electric current.
Magnetic flux is densest and magnetic force is strongest at the ? of a magnet.	poles
A ? is surrounded by a magnetic field that enters the south and exits the north pole.	bar magnet
The molecular theory of magnetism states that ? materials are made up of a very large number of molecular domains that can be arranged in either a disorganized or organized manner.	ferromagnetic
The relative permeability of air is ? .	1.0000004
A(n) ? material is a material that can be very weakly magnetized in the opposite direction when a magnetic field is applied.	diamagnetic
true or false Electromagnetism is a permanent magnetic force.	False Electromagnetism is a temporary magnetic force because the magnetic field is present only as long as current flows.
true or false Permanent magnets may be demagnetized by high temperatures.	true
For an electromagnet, a more permeable core strengthens the ?	concentration of magnetic flux
? is the condition where substantially all the magnetic domains in a magnetic core are aligned with the field and any increases in current no longer result in a stronger electromagnet.	Saturation
true or false With DC, both the current and magnetic field applied to a conductor start at zero and increase almost instantly to maximum value when a switch is closed; both drop to zero when the switch is opened.	True
Every time the current passes the ? point of the AC sine wave, the direction of current flow and polarity of the magnetic field change.	zero
The theory that current flows from the negative terminal to the positive terminal is called ? current flow.	electron
The requirements for induction are: ? , a magnetic field, and relative motion between the conductor and the magnetic field.	a conductor
? in a circuit generates inductive reactance (XL), which is a counter voltage that opposes the source and resists change in the current flow.	Self-induction
The ? rule is an explanation of the direction of a magnetic field around a coil relative to the direction of the current in the coil, where a left hand is used to illustrate the relationship.	left-hand coil
true or false The left-hand conductor rule describes the direction of a magnetic field around a conductor relative to the direction of the current in the conductor.	true
t/f right-hand coil rule is an explanation of the relationship between the direction of the applied current in a conductor, the direction of the magnetic field around the conductor, and the direction of the induced motion of the conductor within a motor.	false
? is the ability of an inductor (coil) in one circuit to induce a voltage in another circuit or conductor.	Mutual induction
With a DC motor, a ? is used to reverse the current direction, which keeps the current flowing in one direction (DC) through the windings to keep the polarity correct in order to interact with the main fields.	commutator When this machine is used as a generator, the commutator provides the current flow in one direction to the load.
? law states that the polarity of induced voltage is such that it produces a current whose magnetic field opposes the change that produced it.	Lenz's
The ability of a material to conduct magnetic flux is its ?	permeability
Mutual induction is the ability of an inductor (coil) in one circuit to ? a voltage in another circuit or conductor.	induce
true or false In the illustration, current flow is positive to negative. This means the illustration shows electron current flow.	false conventional current flow is current flow from positive to negative. Electron current flow is current flow from negative to positive.
In the illustration, a magnetic field in the primary induces a voltage in the secondary. This means that the illustration shows ? induction.	mutual
true or false To maintain continuous rotation in an AC motor, a commutator is used to reverse the direction of the current.	false A commutator is used to reverse the direction of the current in a DC motor. With an AC motor, the current automatically reverses direction because of the alternating current source.
What is the approximate operating time for a Size-1 motor starter?	26 ms
The ability of a material to retain residual magnetism is called ? .	permanence

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lesson 1 magnetism & induction