Magnetism and Electromagnetism

Question 1

What do magnets do?

Answer 1

Magnets repel and attract other magnets and attract magnetic materials.

Question 2

What happens when like poles of magnets are brought together?

Answer 2

Like poles repel.

Question 3

What happens when opposite poles of magnets are brought together?

Answer 3

Opposite poles attract.

Question 4

Define non-magnetic materials.

Answer 4

Materials that are not attracted to magnets and cannot be magnetised (e.g. glass, plastic).

Question 5

Define magnetic materials.

Answer 5

Materials that are attracted to magnets and can be magnetised (e.g. iron, steel, cobalt, nickel).

Question 6

How can magnetism be induced in magnetic materials?

Answer 6

By placing them in a magnetic field.

Question 7

What are magnetically hard materials?

Answer 7

Magnetic materials that can be permanently magnetised (e.g. steel).

Question 8

What are magnetically soft materials?

Answer 8

Magnetic materials that are only temporarily magnetised (e.g. soft iron).

Question 9

What occurs in bulk material regarding magnetic domains?

Answer 9

The domains usually cancel, leaving the material unmagnetized.

Question 10

What do magnetic field lines represent?

Answer 10

The magnetic force on a north pole at a given point.

Question 11

What does the direction of a magnetic field line indicate?

Answer 11

The direction of the force.

Question 12

What does the spacing of magnetic field lines indicate?

Answer 12

The magnitude of the force.

Question 13

From where to where do field lines from magnets point?

Answer 13

From north to south.

Question 14

Describe the uniform magnetic field between two magnets.

Answer 14

Field lines move from the north pole of one straight towards the south pole of the other, are parallel and evenly spaced.

Question 15

What does an electric current passing through a conductor produce?

Answer 15

A magnetic field around it.

Question 16

What is the motor effect?

Answer 16

The phenomenon where the direction of force, field, and current determines movement.

Question 17

What happens if the current or magnetic field is reversed in a motor?

Answer 17

The force will be reversed.

Question 18

How does increasing the magnitude of the current or magnetic field affect the force?

Answer 18

The magnitude of the force will increase.

Question 19

What are the main components of a DC motor?

Answer 19

A coil of wire, two permanent magnets, and a split ring commutator.

Question 20

What does a DC motor do when direct current flows through the wire?

Answer 20

It experiences a turning effect due to forces exerted in the magnetic field.

Question 21

How can the turning effect in a DC motor be increased?

Answer 21

By:
* Increasing the current
* Using a stronger magnetic field
* Increasing the number of turns on the coil.

Question 22

What is the function of a split ring commutator in a DC motor?

Answer 22

To ensure that the direction of current flow in the coil reverses every half turn.

Question 23

How do loudspeakers produce sound?

Answer 23

By using a coil attached to a cone in a magnetic field with alternating current.

Question 24

What effect does changing the frequency of alternating current have on sound produced by a loudspeaker?

Answer 24

It alters the frequency and therefore pitch of the sound.

Question 25

What is electromagnetic induction?

Answer 25

The process where a voltage is induced due to relative movement between a conducting wire and a magnetic field.

Question 26

What is the generator effect?

Answer 26

The induction of voltage when a conducting wire moves across a magnetic field.

Question 27

How can induced voltage be increased in electromagnetic induction?

Answer 27

By:
* Moving the wire more quickly
* Using a stronger magnetic field
* Increasing the length of the wire inside the magnetic field.

Question 28

What occurs when a magnet is moved into a coil?

Answer 28

A voltage is induced in the coil.

Question 29

Fill in the blank: The more quickly the magnetic field changes, the greater the _______.

Answer 29

voltage

Question 30

What are two methods of generating electricity?

Answer 30

Rotating a magnet within a coil or rotating a coil in a magnetic field

These methods exploit electromagnetic induction.

Question 31

What happens as a magnet or coil rotates?

Answer 31

The magnetic field through the coil changes, inducing a voltage and current in the coil

This phenomenon is known as electromagnetic induction.

Question 32

What are three ways to increase the voltage generated in a coil?

Answer 32

• Increasing the length of wire inside the magnetic field
• Using a stronger magnet
• Increasing the speed of rotation

These factors enhance the electromagnetic induction process.

Question 33

Fill in the blank: Electricity can be generated by _______ a magnet within a coil.

Answer 33

rotating

This is a fundamental principle of electromagnetic induction.

Question 34

True or False: A longer wire inside the magnetic field decreases the voltage generated.

Answer 34

False

A longer wire increases the voltage due to more interaction with the magnetic field.

Question 35

What is the effect of using a stronger magnet on voltage generation?

Answer 35

It increases the voltage generated

Stronger magnets induce a greater magnetic field change.

Question 36

What role does the speed of rotation play in electricity generation?

Answer 36

Increasing the speed of rotation increases the voltage generated

Faster rotation results in a quicker change in the magnetic field.