Generators

Question 1

Define flux.

Answer 1

Magnetic material of force surrounding

Flux refers to the total magnetic field passing through a given area.

Question 2

Define flux density.

Answer 2

Number of magnetic lines of force per unit area

Flux density quantifies the strength of the magnetic field in a specific area.

Question 3

Define reluctance.

Answer 3

Opposition of a material to carry magnetic flux

Reluctance is analogous to electrical resistance in magnetic circuits.

Question 4

Define residual magnetism.

Answer 4

Magnetic effect that remains in a material after the magnetizing force is removed

Residual magnetism is often a result of hysteresis in magnetic materials.

Question 5

Define retentivity.

Answer 5

Level of ability of a material to retain residual magnetism

Retentivity is important for materials used in permanent magnets.

Question 6

Define permeability.

Answer 6

The ability of a material to concentrate magnetic flux compared to a vacuum

Higher permeability indicates a material can support a higher magnetic field.

Question 7

Define saturation.

Answer 7

Saturation is reached when any increase in magnetizing force will not produce an increase in magnetism within the material

At saturation, the material cannot be magnetized further regardless of the applied magnetic field.

Question 8

Describe electromagnets.

Answer 8

The magnetic property of a conductor when current flows through it

Electromagnets are created by winding a wire into a coil and passing an electric current through it, generating a magnetic field.

Question 9

What is a magnetic material?

Answer 9

Materials that are strongly attracted by magnets.

Question 10

What are the two classifications of magnets?

Answer 10

• Temporary
• Permanent

Question 11

What is a magnetic pole?

Answer 11

A region that attracts magnetic materials such as iron or steel.

Question 12

Describe the two behaviours of the lines of force of a magnet.

Answer 12

• Take the easiest path between opposite poles
• They do not cross each other

Question 13

Describe the two behaviours of magnetic poles when they are placed next to each other.

Answer 13

• Like poles repel each other
• Unlike poles attract each other

Question 14

In what direction do the imaginary magnetic lines of force of a closed loop flow?

Answer 14

• From the north pole to the south pole
• From the south pole to the north pole

Question 15

Which materials are strongly attracted by magnets?

Answer 15

Iron, nickel, cobalt

These are classified as ferromagnetic materials.

Question 16

Which materials are only slightly attracted by magnets?

Answer 16

Platinum, aluminum

These materials are not as magnetic as ferromagnetic materials.

Question 17

What are ferromagnetic materials?

Answer 17

Metals that are magnetized easily, such as iron, nickel, cobalt, manganese

Ferromagnetic materials exhibit strong magnetic properties.

Question 18

What are paramagnetic materials?

Answer 18

Metals that can be magnetized but not as easily, such as platinum, chromium

Paramagnetic materials have weaker magnetic properties compared to ferromagnetic materials.

Question 19

What are diamagnetic materials?

Answer 19

Metals and non-metals that cannot be magnetized, such as copper, brass, antimony

Diamagnetic materials repel magnetic fields.

Question 20

What is magnetism?

Answer 20

A measurable characteristic of a moving electrical charge

Magnetism is fundamental to electromagnetic theory.

Question 21

How are magnets classified?

Answer 21

1. Temporary
2. Permanent

This classification is based on their ability to retain magnetism.

Question 22

What effect does decreasing the current in a conductor have on the magnetic field around the conductor?

Answer 22

Magnetic field decreases

This indicates an inverse relationship between current and magnetic field strength.

Question 23

What happens to the magnetic field around the conductor if the current in a conductor is switched off?

Answer 23

Magnetic field around the conductor collapses

This indicates that the magnetic field is dependent on the presence of current.

Question 24

When using the left-hand rule for conductors, what does the thumb indicate?

Answer 24

The thumb points in the direction of the electron flow in the conductor

This rule is a mnemonic to determine the direction of force in electromagnetic contexts.

Question 25

If the electron flow is into the page, will the direction of the lines of force be clockwise or counterclockwise?

Answer 25

Counter clockwise ## Footnote The direction of the magnetic field can be visualized using the right-hand grip rule as well.

Question 26

What happens to the direction of the lines of force when the direction of the current flow is reversed?

Answer 26

The direction of the lines of force also reverses ## Footnote This shows the direct correlation between current direction and magnetic field direction.

Question 27

Indicate the north and south poles of the coils in Figure 24.

Answer 27

N ## Footnote The specific orientation of poles is crucial for understanding magnetic fields in coils.

Question 28

What three factors affect the strength of the magnetic field around a coil?

Answer 28

* Amount of current through the coil * The number of turns on the coil * The core material ## Footnote These factors collectively determine the intensity of the magnetic field generated by the coil.

Question 29

What effect does decreasing the current in a conductor have on the magnetic field around the conductor?

Answer 29

Magnetic field decreases ## Footnote This indicates an inverse relationship between current and magnetic field strength.

Question 30

What happens to the magnetic field around the conductor if the current in a conductor is switched off?

Answer 30

Magnetic field around the conductor collapses ## Footnote This indicates that the magnetic field is dependent on the presence of current.

Question 31

When using the left-hand rule for conductors, what does the thumb indicate?

Answer 31

The thumb points in the direction of the electron flow in the conductor ## Footnote This rule is a mnemonic to determine the direction of force in electromagnetic contexts.

Question 32

If the electron flow is into the page, will the direction of the lines of force be clockwise or counterclockwise?

Answer 32

Counter clockwise ## Footnote The direction of the magnetic field can be visualized using the right-hand grip rule as well.

Question 33

What happens to the direction of the lines of force when the direction of the current flow is reversed?

Answer 33

The direction of the lines of force also reverses ## Footnote This shows the direct correlation between current direction and magnetic field direction.

Question 34

Indicate the north and south poles of the coils in Figure 24.

Answer 34

N ## Footnote The specific orientation of poles is crucial for understanding magnetic fields in coils.

Question 35

What three factors affect the strength of the magnetic field around a coil?

Answer 35

* Amount of current through the coil * The number of turns on the coil * The core material ## Footnote These factors collectively determine the intensity of the magnetic field generated by the coil.

Question 36

What happens to the strength of the magnetic field when electricity is applied?

Answer 36

The strength of the magnetic field decreases ## Footnote This is based on the relationship between electric current and magnetic field strength.

Question 37

Why is silicon steel used to make cores for coils?

Answer 37

Cores made of silicon steel reduce hysteresis losses ## Footnote Silicon steel has properties that minimize energy loss during magnetization.

Question 38

Name two types of iron loss that can occur in the core of an electromagnet.

Answer 38

* Eddy currents * Hysteresis ## Footnote Eddy currents are loops of electric current induced within conductors by a changing magnetic field.

Question 39

Why are iron coil cores laminated?

Answer 39

To reduce eddy current losses ## Footnote Laminating the core helps to interrupt the paths for eddy currents.

Question 40

Define hysteresis.

Answer 40

The heat produced due to the lagging of magnetic domains in an iron core ## Footnote Hysteresis represents energy loss when the magnetization of a material lags behind the applied magnetic field.

Question 41

When are eddy currents produced?

Answer 41

When a magnetic core is subjected to a changing magnetic field ## Footnote This occurs due to Faraday's law of electromagnetic induction.

Question 42

When does the core of an electromagnet become saturated?

Answer 42

When an increase in current in the coil does not produce an increase in magnetism in the core ## Footnote Saturation occurs when all magnetic domains are aligned and cannot align further.

Question 43

What is faradays law of induction?

Answer 43

When there is change in a magnetic field within a closed loop it induces an EMF in the conductor