Magnetism

Question 1

What is a permanent magnet?

Answer 1

A magnet that has its own magnetic field

Question 2

What is an induced magnet?

Answer 2

An object that can be magnetized by a magnetic field

Question 3

What materials can a magnet be made from?

Answer 3

iron, steel, cobalt, nickel

Question 4

What force does induced magnetism cause?

Answer 4

Attraction

Question 5

What happens to induced magnets after the magnetic field is removed?

Answer 5

Lose magnetism

Question 6

What is a magnetic field?

Answer 6

A region around a magnet where a force acts on other magnets / magnetic materials

Question 7

Further away from magnetic field = ?

Answer 7

Weaker force

Question 8

How can you find the direction of a magnetic field?

Answer 8

With a small compass

Question 9

How can we prove the earth’s core is magnetic?

Answer 9

Hold a compass away from other magnets - needle will point north / south.

Question 10

Current flowing though a wire produces a?

Answer 10

Magnetic field

Question 11

How can we prove current flowing through a wire produces a magnetic field?

Answer 11

By holding a small compass next to the wire and turn circuit on / off - needle will point towards the circuit

Question 12

What does magnetic field strength depend on in a wire?

Answer 12

• Current flowing through wire

Question 13

What is the right hand grip rule?

Answer 13

Place right hand in direction of current flow - fingers will curl in the direction of the magnetic field (in a coil)

Question 14

What is a coiled wire called?

Answer 14

Solenoid

Question 15

What type of magnetic field does a solenoid produce?

Answer 15

A strong, uniform magnetic field on the inside of the solenoid

Question 16

How can we improve the strength of a solenoid’s magnetic field?

Answer 16

Increase current
Increase amount of coils
Add an iron core

Question 17

How many circuits does a relay contain?

Answer 17

2

Question 18

What is the motor effect?

Answer 18

When a magnetic field of a wire interacts with the magnetic field of 2 other magnets, producing a force.`

Question 19

What is magnetic flux density?

Answer 19

Strength of the magnetic field

Question 20

What direction must be wire be at for the motor effect to work?

Answer 20

90deg to the direction of the magnetic field

Question 21

How do you determine for force’s direction in the motor effect?

Answer 21

Using the left hand rule

Question 22

What is the left hand rule?

Answer 22

Place thumb, 1st finger and 2nd finger at 90deg angles to each other.
Point 1st finger in the direction of the magnetic field (North - South)
Point 2nd finger in direction of current.
Thumb shows force direction

Question 23

What is a split - ring commutator?

Answer 23

A split metal ring in contact with 2 brushes

Question 24

What does the split - ring commutator do?

Answer 24

Changes the direction of current flow in a motor

Question 25

How does a moving - coil loudspeaker work?

Answer 25

A cone has a coil of wire wrapped around one end The coil is connected to an AC power supply Current flowing through the coil generates a magnetic field, interacting the the permanent magnet on the inside of the coil. Produces a resultant force which moves the cone

Question 26

What does increasing the current do to a speaker?`

Answer 26

It increases the amplitude of the coil's movements This means that the cone is moving more air, so the sound is louder.

Question 27

What is an alternator?

Answer 27

A coil of wire rotating in a magnetic field

Question 28

What is the coil connected to in an alternator?

Answer 28

2 metal commutators

Question 29

What is the role of a commutator?

Answer 29

To allow the current to pass out of a coil

Question 30

When do we see the maximum potential difference in an alternator / dynamo?

Answer 30

When the coil moves through the magnetic field (horizontal)

Question 31

When do we see no potential difference in an alternator / dynamo

Answer 31

When the coil isn't moving through the magnetic field (vertical)

Question 32

What causes the potential difference to reverse direction in an alternator?

Answer 32

When the coil starts moving in a different direction

Question 33

Why does an alternator produce alternating current?

Answer 33

Because the coil is connected to a split ring commutator

Question 34

How do we increase the size of an alternating current?

Answer 34

Increase magnetic field strength Increase coil turns Increase coil size

Question 35

What happens if rotation speed is increased in an alternator / dynamo?

Answer 35

Amplitude of the potential difference increases Frequency increases

Question 36

Why does a dynamo produce a direct current?

Answer 36

It uses a split - ring commutator instead of 2 separate ones - both ends of the coil are connected to the same commutator

Question 37

Sound waves hit a diaphragm, causing it to ___ ?

Answer 37

Vibrate

Question 38

What happens to the coiled wire as the diaphragm moves (microphone)

Answer 38

It moves in and out of the magnetic field, inducing potential difference across the ends of the wire

Question 39

What happens to the potential difference as the coil moves backwards / forwards?

Answer 39

It switches direction

Question 40

What is the frequency of the change in potential difference equal to (microphone)

Answer 40

Sound wave frequency

Question 41

How many coils in a transformer?

Answer 41

2

Question 42

The primary coil is connected to an ____ ?

Answer 42

Alternating current

Question 43

As the current flows through the primary coil, it generates a _____ .

Answer 43

Changing magnetic field

Question 44

The changing magnetic field passes along the _____ and through the _____.

Answer 44

Iron core, secondary coil

Question 45

Transformers only work with ______.

Answer 45

Alternating current

Question 46

Why do transformers not work with direct current?

Answer 46

They produce a constant magnetic field

Question 47

What is a step up transformer?

Answer 47

A transformer that increases voltage

Question 48

What is a step down transformer?

Answer 48

A transformer that decreases voltage

Question 49

In a transformer, power must be _____.

Answer 49

Conserved