Magnetism & Electromagnets

Question 1

Magnetic moments align to form …

Answer 1

Domains

Question 2

What type of magnet do speakers use?

Answer 2

A permanent magnet

Question 3

A point on a magnet where the force of attraction is strongest?

Answer 3

A Pole

Question 4

The magnetic effect of a material is caused by this atomic particle?

Answer 4

An electron

Question 5

Lines of magnetic force around a magnet are called…

Answer 5

Flux

Question 6

Lines of flux flow from which pole?

Answer 6

The North Pole

Question 7

What is magnetite?

Answer 7

A naturally occurring magnetic material.

Question 8

Magnetic flux is symbolized by what Greek letter?

Answer 8

Phi

Question 9

Which pole do magnetic lines of flux flow into?

Answer 9

The South Pole

Question 10

What is reluctance?

Answer 10

The opposition to magnetic flux

Question 11

What is saturation?

Answer 11

When the maximum magnetism of a material is reached.

Question 12

List three factors that affect the strength of an electromagnet.

Answer 12

1. The amount of current in the coil.
2. The number of turns on the coil.
3. The type of core that is part of the magnetic field.

Question 13

Define hysteresis losses

Answer 13

It is the undesired heat production from the flip-flopping of the magnetic domains.

Question 14

The heat produced by circulating currents in the core caused by the changing magnetic field are called?

Answer 14

Eddy currents.

Question 15

What are two methods that are used to reduce the effects of hysteresis losses and eddy currents?

Answer 15

Silicon steel and laminations between sheets in the core.

Question 16

What is the symbol for Inductance and what is its unit of measurement?

Answer 16

“L” and the unit of measurement is henry (H)

Question 17

Creating a voltage on a different circuit from the source when they share the same core is called?

Answer 17

Mutual inductance

Question 18

Using the left hand rule for COILS, the fingertips point in the direction of _________ and the thumb indicates __________.

Answer 18

1. Electron Flow

2. North Pole

Question 19

What is Lenz’s Law defined as…

Answer 19

Induced voltage opposes the cause that produced it.

Question 20

What is a magnet that’s created by energizing a coil of wire?

Answer 20

An electromagnet

Question 21

Define retentivity

Answer 21

It is the ability of a material to retain magnetism

Question 22

What is permeability

Answer 22

It is a material property that determines the ease with which magnetic flux magnetizes that material.

Question 23

Materials used to make permanent magnets are?

Answer 23

Cobalt
Molybdenum
Chrome-tungsten and
Alnico - which is the most common

Question 24

What are permanent magnets used for?

Answer 24

Permanent magnet motors
Magnetos
Megohmmeters 
Speakers and
Analog meters

Question 25

Temporary magnets are used for

Answer 25

Door chimes
Relays
Contactors and
Motors