6- Magnetism + Electromagnetism

Question 1

What are properties of magnetically soft materials?

Answer 1

• easy to magnetise
• easily lose their magnetism
• temporarily magnetised

Question 2

What are some properties of magnetically hard materials?

Answer 2

• difficult to magnetise
• do not easily lose their magnetism
• permanently magnetised

Question 3

What are permanent magnets made out of?

Answer 3

Magnetically hard materials

Question 4

What are electromagnets made out of?

Answer 4

Magnetically soft materials

Question 5

What is a magnetic field?

Answer 5

The region around a magnet where a force acts on another magnet or on a magnetic material

Question 6

When is a uniform filed created?

Answer 6

when two opposite poles are held close together

Question 7

What are examples of magnetic materials?

Answer 7

Iron
Cobalt
Nickel
Steel

Question 8

What are properties of permanent magnets?

Answer 8

• do not lose their magnetism

- produce their own magnetic fields

Question 9

What is an induced magnet?

Answer 9

When a magnetic material is placed in a magnetic field - can lose magnetism quickly

Question 10

What is electromagnetism?

Answer 10

When a current flows through a conducting wire a magnetic field is produced around the wire

Question 11

How can you make the magnetic field stronger?

Answer 11

Increase current

More coils

Question 12

How does the motor effect occur?

Answer 12

When two magnetic fields interact to produce the force on the wire

Question 13

Explain the motor effect?

Answer 13

• when the two magnetic fields interact, each side of the coil feels a force in opposite directions
• the coil rotates
• the commutator changes direction of current in the coil every half turn
• current flows in same direction relative to permanent magnet

Question 14

How can the speed at which the coil rotates be increased by: (in motor)

Answer 14

• Increasing the current

- Increasing the strength of the magnetic field

Question 15

How can the direction of rotation of coil in the motor be changed by?

Answer 15

• Reversing the direction of the current

- Reversing the direction of the magnetic field by reversing the poles of the magnet

Question 16

How can the force supplied by the motor be increased by?

Answer 16

• Increasing the current in the coil
• Increasing the strength of the magnetic field
• Adding more turns to the coil

Question 17

What does a loudspeaker consist of?

Answer 17

a coil of wire which is wrapped around one pole of a permanent magnet

Question 18

How does a loudspeaker work?

Answer 18

• An ALTERNATING current passes through the coil creating CHANGING magnetic field around the coil
• current is constantly changing direction, + direction of the magnetic field,
• The magnetic field produced around the coil interacts with the field from the permanent magnet
• The interacting magnetic fields will exert a force on the coil
• the coil then oscillates, creating sound waves

Question 19

How can a wire experience full force?

Answer 19

The wire needs to be 90 degrees to the magnetic field

Question 20

How does the force on a wire act?

Answer 20

In the same direction relative to the magnetic field of the magnets and the direction of the current in the wire.

Question 21

The magnitude of the force increases with ….?

Answer 21

The strength of the magnetic field

Question 22

Reversing the current or the magnetic field also reverses the …?

Answer 22

Direction of the force

Question 23

The force increases with the…?

Answer 23

Amount of current passing through the conductor

Question 24

When will a charged particle not feel a force?

Answer 24

When the motion is parallel to the field

Question 25

Give examples of uses for electromagnets and electric motors?

Answer 25

Bells, loudspeakers + headphones

Question 26

What is Electromagnetic induction?

Answer 26

When a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it.

Question 27

How does the generator effect take place?

Answer 27

by the conductor or coil cutting through the magnetic field lines of the magnetic field

Question 28

When will a potential difference be induced in the conductor?

Answer 28

if there is relative movement between the conductor and the magnetic field

Question 29

If the conductor is part of a complete circuit then where is the current induced

Answer 29

In the conductor

Question 30

What is a simple alternator

Answer 30

a type of generator that converts mechanical energy to electrical energy in the form of alternating current

Question 31

What does a basic transformer consist of ?

Answer 31

A primary coil A secondary coil An iron core

Question 32

What does a transformer do ?

Answer 32

- An alternating current (which changes direction) supplied to the primary coil - the changing magnetic field passes through the iron core - there is now a changing magnetic field inside the secondary coil - changing field cuts through the secondary coil and induces a potential difference - If the secondary coil is part of a complete circuit it will cause an alternating current to flow

Question 33

What does a step up transformer have ?

Answer 33

More turns on the secondary coil than the primary coil

Question 34

What do step up transformers do to the voltage?

Answer 34

Increase the voltage

Question 35

What do step down transformers do to voltage ?

Answer 35

Decrease the voltage

Question 36

What does a step down transformer have?

Answer 36

More turns on the primary coil than the secondary

Question 37

What is a step up transformer used for across the country?

Answer 37

To boost the voltage before it is transmitted

Question 38

What is a step down transformer used for across the country?

Answer 38

To reduce the voltage so it is more useful and safer to use