A/C, D/C, and Magnetism - Part 1

Earth contains magnetic poles.

True

_______________ materials are either metal or nonmetal materials that cannot be magnetized.

diamagnetic

_______________ materials are metals that are easily magnetized.

ferromagnetic

When a conductor cuts magnetic lines of force, a voltage is induced into the conductor. This principle is called _____.

Electromagnetic induction

When using the left-hand generator rule, the thumb points to the direction of _____.

Thrust

The horsepower rating of three-phase motors and the kilovolt-ampere rating of three-phase transformers are about _____ greater than for single-phase motors or transformers with a similar frame size.

150%

A basic law of magnetism states that unlike poles _____ and like poles _____.

Attract, repel.

Electrons can form spin patterns that _____ the magnetic field of the material.

Cancel

The angular difference between true north and magnetic north is known as the angle of _____.

Declination

If an object is placed in the field of an strong electromagnet connected to an AC line, the object will be _____.

Demagnetized

The direction of induced current can be determined by using the _____ left-hand generator rule.

Fleming

A magnet that produces a magnetic field as long as current is flowing is called a(n) _____ magnet.

Electromagnets

Magnetism can be explained in terms of _____ spin patterns.

Electrons

In three-phase power systems, the delivered power _____.

Never falls to zero

_____ do not require any power of force to maintain their field.

Permanent magnets

Magnetic lines of force are called _____.

Flux

The three substances that form natural magnets are _____.

Iron, nickel, and cobalt.

If current is flowing in a circuit containing an inductor and the power switch is opened, the magnetic filed surrounding the inductor collapses and induces voltage into the inductor, resulting in a voltage spike.

True

Man-made permanent magnets retain their magnetism _____ than natural magnets.

Longer

Lodestone is a name for a naturally occurring magnetic material that is also called _____.

Magnetite

The measure of a material's ability to be magnetized is called _____.

Permeability

The time required for current in an inductor to reach its full Ohm's law value is called the _____ time constant.

R-L

The measure of a material's resistance to magnetism is _____.

Reluctance

The north magnetic pole of a compass needle is attracted to the _____ magnetic pole of the earth.

South

The amount of voltage induced into a conductor depends on the turns of wire, the strength of the magnetic field, and the speed of cutting action.

True

In the English system of measure, magnetic strength is measured in a term called _____."

Flux density

When a magnetic materials molecules are all lined up, and increases in current flow no longer cause increases in magnetic field strength, the material has reached _____.

Saturation

The north pole of a compass needle points in the direction of the south geographic pole.

True

To locate the north pole of an electromagnet, use the _____ hand rule.

left

The amount of magnetism left in a material after the magnetizing force has stopped is called _____.

residual magnetism

If a voltage is being induced into a conductor by electromagnetic induction, reversing the direction of motion of the conductor will _____.

reverse the polarity of the induced voltage

The strength of an electromagnet is primarily proportional to its _____.

ampere-turns

When using the left-hand generator rule, the center finger points to the direction of _____.

Flux

A way of determining the relationships of the motion of the conductor, the magnetic field direction, and the direction of the induced current is by using the _____.

Left-hand generator rule