magnetic fields

Question 1

what is a magnetic field?

Answer 1

a region where other magnets or magnetic materials experience a force

Question 2

what is the relationship with the line and magnetic fields?

Answer 2

the closer together the lines are, the stronger the magnetic field

Question 3

where is the magnetic field strongest?

Answer 3

at the poles of a magnet

Question 4

how is a uniform field created?

Answer 4

when you place a north and south pole of two bar magnets near each other

Question 5

what do you need to draw a uniform field?

Answer 5

at least three field lines that are parallel to each other and are all the same distance

Question 6

when not near a magnet why do compasses point to the north?

Answer 6

because earth generates its own magnetic field so the core of the earth is magnetic

Question 7

what are the three main magnetic materials?

Answer 7

iron
nickel
cobalt

Question 8

why is steel magnetic?

Answer 8

because it contains iron

Question 9

what is the magnetic force between a magnet and magnetic material?

Answer 9

attractive

Question 10

what are permanent magnetics?

Answer 10

produce their own magnetic field

Question 11

what are induced magnets?

Answer 11

only produce a magnetic field while they are in another magnetic field

Question 12

why is a force between a magnet and a magnetic material always attractive?

Answer 12

because the south pole induces the north pole and vice versa

Question 13

magnetically soft materials

Answer 13

loose their magnetism very quickly

Question 14

magnetically hard materials

Answer 14

lose their magnetism more slowly

Question 15

uses of magnetic materials

Answer 15

fridge doors
cranes
doorbells
speakers

Question 16

how is a magnetic field created?

Answer 16

when a current flows through a long straight conductor

Question 17

what is the field made up of?

Answer 17

concentric circles

Question 18

what does changing the direction of the current effect?

Answer 18

the direction of the magnetic field

Question 19

what is the right hand thumb rule?

Answer 19

point your thumb in the direction of current and curl fingers

Question 20

what does the right hand thumb rule show?

Answer 20

the direction of the field where your finger is pointing

Question 21

what is the motor effect?

Answer 21

a current in a magnetic field experiences a force

Question 22

How is a force created on a wire?

Answer 22

when a current carrying conductor is put between magnetic poles and the fields interact

Question 23

how does the wire experience the full force?

Answer 23

if it is at 90 degrees to the magnetic field

Question 24

what is flemmings left hand rule used for?

Answer 24

find the direction of the force on a current carrying conductor

Question 25

what does your first finger do in the left hand rule?

Answer 25

points in the direction of the magnetic field

Question 26

what does your second finger show in the left hand rule?

Answer 26

the direction of the current

Question 27

what does your thumb show in the left hand rule?

Answer 27

point in the direction of the force

Question 28

how do you find the size of the force?

Answer 28

magnetic flux density * current * length

Question 29

what is magnetic flux density?

Answer 29

how many field flux lines there are in a region

Question 30

what does magnetic flux density show?

Answer 30

strength of the magnetic field

Question 31

when do you use the equation for force size?

Answer 31

when the current is at 90 degrees

Question 32

what is a solenoid?

Answer 32

a long coil of wire

Question 33

how to increase the strength of a magnetic field produced by a length of wire?

Answer 33

wrapping it into a long cool with lots of loops

Question 34

what is the magnetic field like in a solenoid?

Answer 34

strong and almost uniform as the lines are pointing in same direction

Question 35

what is the field like outside the solenoid?

Answer 35

week apart from at the ends as the lines cancel each other out

Question 36

what does the direction of the field depend on?

Answer 36

the direction of the current

Question 37

what is a solenoid an example of?

Answer 37

an electromagnet

Question 38

what is an electromagnet?

Answer 38

a magnet with a magnetic field that can be turned on and off using an electric current

Question 39

how can you increase the strength of a solenoid?

Answer 39

putting a block of iron in the centre of the coil

Question 40

how does iron increase the strength of a solenoid?

Answer 40

it acts as an induced magnet

Question 41

what does induce mean?

Answer 41

creates

Question 42

what is electromagnetic induction ?

Answer 42

the induction of a potential difference in a wire which is experiencing a change in magnetic field

Question 43

what are the two situations where you get an electromagnetic induction?

Answer 43

electrical conductor | magnetic field

Question 44

how do you produce an alternating current ?

Answer 44

if you keep the magnet moving backwards and forwards or keep it rotating in the same direction

Question 45

how do you reverse current?

Answer 45

if you move or rotate the magnet in the opposite direction

Question 46

how do you get an induced potential difference?

Answer 46

when a magnetic field through an electrical conductor changes

Question 47

How do you increase the size of the induced potential difference?

Answer 47

increase the strength of field increase speed of movement having more turns per unit length of coil

Question 48

what happens when a current is induced?

Answer 48

produced its own magnetic field that acts against the change trying to return things to what they were

Question 49

what do transformers do?

Answer 49

use induction to change the size of the potential difference of an alternating current

Question 50

what happens when an alternating p.d is applied across a primary coil?

Answer 50

it produces an alternating magnetic field

Question 51

what happens to the magnetisation in the core in the primary coil?

Answer 51

it also alternates as easily magnetised

Question 52

what is the result of the primary coil alternating?

Answer 52

the magnetic field inducing potential difference in a secondary coil changes

Question 53

step up transformers

Answer 53

step up the potential difference as have more turns on secondary coil then primary

Question 54

step down transformers

Answer 54

step down the potential difference as have more turns on primary coil then secondary

Question 55

what can you assume about the input and output power?

Answer 55

that they will be equal

Question 56

what do transformers in the national grid produce?

Answer 56

high potential difference and low current

Question 57

how can you make the national grid more efficient?

Answer 57

higher voltage low resistance cables transformers are used

Question 58

how are step down transformers used in the national grid?

Answer 58

bring down the p.d to safe usable levels for consumers