LVL 1
________ is used to convert electrical energy to a rotating mechanical force on a motor's shaft.
Electromagnetism
A(n) ____ material is a material that can be very weakly magnetized in the opposite direction when a magnetic field is applied.
diamagnetic
The ability of a material to conduct magnetic flux is its ____.
permeability
The ability of a material to retain residual magnetism is called _____?
permanence
What is magnetic flux?
The invisible lines of force that make up the total quantity of a magnetic field.
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
Magnetic flux is densest and magnetic force is strongest at the ____ of the magent.
poles
A ____ is surrounded by a magnetic field that enters the south and exits the north pole.
bar magnet
_____ is the ability of an inductor (coil) in one circuit to induce a voltage in another circuit or conductor.
Mutual induction
What is a permanent magnet?
A magnet that can hold its magnetism together for a long period.
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
For an electromagnet, a more permeable core strengthens the _____.
concentration of magnetic flux.
The requirements for induction are: _____, a magnetic field, and relative motion between the conductor and the magnetic field.
a conductor
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
The theory that current flows from the negative terminal to the positive terminal is called ____ current flow.
electron
True or False:
Lenz’s Law states that the induced voltage in a circuit opposes the change that produced it.
True
True or False:
Magnetic flux density is highest at the center of a magnet.
False
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
Permeability is usually described relative to the permeability of what?
A perfect vacuum
Which rule is used to explain the relationship between current, magnetic field, and induced motion in a motor?
Right-hand motor rule
The relative permeability of air is ___.
1.0000004
What is the difference between magnetic flux and magnetic flux density?
Magnetic flux density is the amount of concentration of magnetic flux through a specific area.
____ 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.
What is the purpose of self-induction in a circuit?
Which theory suggests that current flows from positive to negative terminals?
conventional current flow theory