Electric Motors Test 1 magnetism and induction Flashcards
Magnetism is used to produce most of the electricity consumed, develop rotary motion in motors, and develop linear motion in solenoids
T
Three common naturally occuring magnetic metals are iron, nickel and cobalt
T
Common temporary magnets are horseshoe magnets, compasses and bar magnets
F
A more concentrated, or denser, magnetic flux makes a weaker magnetic force
F
All magnets have a north and south pole
T
A material is nonmagnetic if it has disorganized molecular domains so that the individual fields cancel each other
T
Any permanent magnet can be demagnetized by a sharp blow or by heat that causes the molecular arrangement to become disorganized.
T
A common ferromagnetic material is copper.
F
The magnetic field around a straight conductor is relatively weak and must be concentrated use in an electric motor
T
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
T
When using the left hand generator rule, it is assumed that the magnetic field is moving and the conductor is initially stationary
F
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.
F
A(n) _______ is a force produced by a magnet that exerts a force on moving electric charges or on other magnets.
magnetic field
A __________ magnet is a magnet that can hold its magnetism for a long period.
permanent
____________ is a measure of the ability of a magnet to retain magnetism after the magnetizing force has been removed.
Retentivity
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.
magnetism
The ______ of a bar magnet can be determined by suspending it from a point overhead and allowing it to turn freely
polarity
A _______ material is a material that can be weakly magnetized in the same direction as the applied magnetic field
paramagnetic
_____ is the temporary magnetic field produced when electricity passes through a conductor.
electromagnetism
______ 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.
electron
________ is the property of a device or circuit that causes it to store energy in an electromagnetic field.
Resistance
________ is the ability of an inductor in a circuit to generate inductive reactance, which opposes the change in current.
Self-induction
______ 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.
Lenz’s
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.
left-hand coil
___________ is a measure of the ability of a material to conduct magnetic flux.
permeability
A(n) _____________ material is a material that is easily magnetized and has high permeability.
ferro-magnetic
________ 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
saturation
_________ is a description of current flow as the flow of positive charges from the positive terminal to the negative terminal of a power source
conventional
_________ is the ability of an inductor(coil) in one circuit to induce a voltage in another circuit or conductor.
mutual induction
____ current applied to a conductor starts at zero and goes to its maximum value almost instantly when a switch is closed.
direct
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.
left-hand conductor
In order to create the continuous motion needed in a motor, the direction of the current must be _____________
alternating
The direction of an electromagnetic field is determined by the direction of the __________________ flowing through the conductor.
current
The current and the strength of the magnetic field decrease if the resistance of the circuit
increase
The three requirements for induction are a conductor, a magnetic field, and ___________ between the conductor and the magnetic field.
motion
__________ is a force by which materials exert an attraction or repulsion on other materials
magnetism
