Electric Motors Test 1 magnetism and induction

Question 1

Magnetism is used to produce most of the electricity consumed, develop rotary motion in motors, and develop linear motion in solenoids

Answer 1

T

Question 2

Three common naturally occuring magnetic metals are iron, nickel and cobalt

Answer 2

T

Question 3

Common temporary magnets are horseshoe magnets, compasses and bar magnets

Answer 3

F

Question 4

A more concentrated, or denser, magnetic flux makes a weaker magnetic force

Answer 4

F

Question 5

All magnets have a north and south pole

Answer 5

T

Question 6

A material is nonmagnetic if it has disorganized molecular domains so that the individual fields cancel each other

Answer 6

T

Question 7

Any permanent magnet can be demagnetized by a sharp blow or by heat that causes the molecular arrangement to become disorganized.

Answer 7

T

Question 8

A common ferromagnetic material is copper.

Answer 8

F

Question 9

The magnetic field around a straight conductor is relatively weak and must be concentrated use in an electric motor

Answer 9

T

Question 10

The strength of a magnetic field is directly proportional to the number of turns in the coil and the amount of current flowing through the conductor

Answer 10

T

Question 11

When using the left hand generator rule, it is assumed that the magnetic field is moving and the conductor is initially stationary

Answer 11

F

Question 12

The right hand motor rule states that with the thumb, index finger, and middle finger of the right hand set at right angles to each other, the index finger points in the direction of the magnetic field, the thumb points in the direction of the motion of the conductor, and the middle finger points in the direction of the induced current.

Answer 12

F

Question 13

A(n) _______ is a force produced by a magnet that exerts a force on moving electric charges or on other magnets.

Answer 13

magnetic field

Question 14

A __________ magnet is a magnet that can hold its magnetism for a long period.

Answer 14

permanent

Question 15

____________ is a measure of the ability of a magnet to retain magnetism after the magnetizing force has been removed.

Answer 15

Retentivity

Question 16

The basic law of ____ states that unlike magnetic poles (N and S) attract each other and like magnetic poles (N and N and S and S) repel each other.

Answer 16

magnetism

Question 17

The ______ of a bar magnet can be determined by suspending it from a point overhead and allowing it to turn freely

Answer 17

polarity

Question 18

A _______ material is a material that can be weakly magnetized in the same direction as the applied magnetic field

Answer 18

paramagnetic

Question 19

_____ is the temporary magnetic field produced when electricity passes through a conductor.

Answer 19

electromagnetism

Question 20

______ current flow is a description of current flow as the flow of electrons from the negative terminal to the positive terminal of a power source.

Answer 20

electron

Question 21

________ is the property of a device or circuit that causes it to store energy in an electromagnetic field.

Answer 21

Resistance

Question 22

________ is the ability of an inductor in a circuit to generate inductive reactance, which opposes the change in current.

Answer 22

Self-induction

Question 23

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

Answer 23

Lenz’s

Question 24

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

Answer 24

left-hand coil

Question 25

___________ is a measure of the ability of a material to conduct magnetic flux.

Answer 25

permeability

Question 26

A(n) _____________ material is a material that is easily magnetized and has high permeability.

Answer 26

ferro-magnetic

Question 27

________ is the condition where a magnetic core has substantially all the magnetic domains aligned with the field and any increases in current no longer result in a stronger elctromagnet

Answer 27

saturation

Question 28

_________ is a description of current flow as the flow of positive charges from the positive terminal to the negative terminal of a power source

Answer 28

conventional

Question 29

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

Answer 29

mutual induction

Question 30

____ current applied to a conductor starts at zero and goes to its maximum value almost instantly when a switch is closed.

Answer 30

direct

Question 31

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

Answer 31

left-hand conductor

Question 32

In order to create the continuous motion needed in a motor, the direction of the current must be _____________

Answer 32

alternating

Question 33

The direction of an electromagnetic field is determined by the direction of the __________________ flowing through the conductor.

Answer 33

current

Question 34

The current and the strength of the magnetic field decrease if the resistance of the circuit

Answer 34

increase

Question 35

The three requirements for induction are a conductor, a magnetic field, and ___________ between the conductor and the magnetic field.

Answer 35

motion

Question 36

__________ is a force by which materials exert an attraction or repulsion on other materials

Answer 36

magnetism