magnetism

Question 1

Magnetic field

Answer 1

A region where other magnets or magnetic materials experience a force

Question 2

What are the four magnetic materials?

Answer 2

=> Iron
=> Steel
=> Nickel
=> Cobalt

Question 3

In which direction do magnetic field lines go?

Answer 3

From north to south pole

Question 4

What do close together magnetic field lines mean?

Answer 4

Stronger

Question 5

Where is the magnetic field the strongest?

Answer 5

Poles

Question 6

What is the force between magnet and magnetic material always?

Answer 6

Attractive, no matter the pole

Question 7

What will happen to like poles?

Answer 7

Repel

Question 8

What will happen to different poles?

Answer 8

Attract

Question 9

What do compasses show and why?

Answer 9

Direction of magnetic fields, since there is a bar magnet inside

Question 10

Permanent magnets

Answer 10

Produce their own magnetic field

Question 11

Induced magnets

Answer 11

Magnetic materials that turn into a magnet when they are put into a magnetic field

Question 12

What does a moving charge create?

Answer 12

A magnetic field which is made up of concentric circles

Question 13

How do you work out the magnetic field direction of a wire with moving charge?

Answer 13

Right-hand grip

Question 14

How to change the strength of magnetic field in a wire?

Answer 14

Changes in current and distance from the wire

Question 15

What is a solenoid?

Answer 15

A coil of wire

Question 16

What does the loop of wire, which line up with each other, result in?

Answer 16

Field lines pointing in the same direction that are very close to each other

Question 17

What are magnetic field lines inside a solenoid like?

Answer 17

Strong and uniform (it has the same strength and direction at every point in that region)

https://physics.stackexchange.com/questions/323326/why-do-magnetic-field-lines-point-towards-the-north-pole-on-the-inside-of-a-sole

Question 18

How can you increase the magnetic field in a solenoid?

Answer 18

Putting a block of iron in the centre of the coil

Question 19

Electromagnet

Answer 19

A type of magnet in which the magnetic field is produced by an electric current.

Question 20

What are the two uses of electromagnets?-

Answer 20

=> Scrap yards, to pick up stuff
=> Used within other circuits to act as switches:
- attracts iron contact on the rocker
- rocker pivots and closes the contacts, completing circuit two, and turning on the motor

Question 21

Motor Effect

Answer 21

A wire carrying a current creates a magnetic field. This can interact with another magnetic field, causing a force that pushes the wire at right angles. This is called the motor effect.

Question 22

In what position does the wire has to be for it to experience the full force?

Answer 22

90°

Question 23

What is the equation to find the force acting on a conductor in a magnetic field?

Answer 23

F= B (magnetic flux density (T, tesla)) x I (current (A)) x l (Length (m))

Question 24

Fleming’s left-hand rule

Answer 24

First finger => Field
Second finger => Current
Thumb => Force (Motion)

Question 25

How can the direction of the motor be reversed?

Answer 25

Swapping polarity of the dc supply or swapping the magnetic poles over

Question 26

What do loudspeakers and headphones use?

Answer 26

Electromagnets

Question 27

Loudspeakers

Answer 27

1. a current in the coil creates a magnetic field 2. the magnetic field interacts with the permanent magnet generating a force, which pushes the cone outwards 3. the current is made to flow in the opposite direction 4. the direction of the magnetic field reverses 5. the force on the cone now pulls it back in 6. repeatedly alternating the current direction makes the cone vibrate in and out 7. the cone vibrations cause pressure variations in the air - which are sound waves

Question 28

Generator Effect

Answer 28

When motion between a conductor and a magnetic field creates electricity, ie a magnet is moved into a coil of wire.

Question 29

How can you produce the generator effect?

Answer 29

Moving a magnet in a coil of wire OR moving a conductor in a magnetic field (cutting magnetic field lines)

Question 30

What will happen if you move the magnet in the opposite direction in the generator effect?

Answer 30

The potential difference/current will be reversed

Question 31

How do you produce an alternating current by the generator effect?

Answer 31

Keep the magnet moving backwards and forwards, which produces a potential difference that keeps swapping direction

Question 32

What does the magnetic field created by an induced current always do?

Answer 32

Acts against the change that made it (wether that is the movement of a wire or a change in the field it is in)

Question 33

How can you increase induced potential difference by doing two things?

Answer 33

=> Increasing the speed of the movement - cutting more magnetic field lines in a given time => Increasing the strength of the magnetic field

Question 34

What do alternators generate?

Answer 34

An alternating current

Question 35

What do alternators use so the contacts do not swap every half term?

Answer 35

Slip rings and brushes

Question 36

What does the alternator produce?

Answer 36

An alternating potential difference

Question 37

What do dynamos generator?

Answer 37

A direct current

Question 38

What do dynamos use so the connections are swapped every half turn to keep the current flowing in the same direction?

Answer 38

Split-ring commutators

Question 39

What can you use to see the generated potential difference?

Answer 39

An oscilloscope

Question 40

Microphone

Answer 40

1) Sound waves hit a flexible diaphragm that is attached to a coil of wire, wrapped around a magnet 2) This causes the coil of wire to move in the magnetic field, which generates a current 3) The movement of the coil (and so the generated current) depends on the properties of the sound wave (louder sounds make the diaphragm move further) 4) This is how microphones can convert the pressure variations of a sound wave into variations in current in an electric circuit

Question 41

What do transformers change the pd for?

Answer 41

Only for alternating current

Question 42

Step-down transformers

Answer 42

Step the PD down. They have more turns on the primary coil than the secondary coil

Question 43

Why does the national grid uses low currents?

Answer 43

Less energy is wasted heating the wires and the surroundings