Magnetism

Question 1

what is a permanent magnet

Answer 1

always produce a magnetic field

Question 2

what is an induced magnet

Answer 2

become magnatised when in another magnet

Question 3

what metals can become magnatised

Answer 3

iron
colbolt
nickel

Question 4

what metals can not become magnatised

Answer 4

aluminium and copper

Question 5

what happens to a electric current flowing through a wire

Answer 5

will produce its own magnetic field

Question 6

what is the motor effect

Answer 6

when a current flowing wire is in another magnetic field it will experience a force

Question 7

how to calculate force f=bil

Answer 7

magnetic flux density(b - tesla) x current x length

Question 8

what will happen between the forces in an induced magnet and a permanent magnet

Answer 8

they will always be attracted

Question 9

what does being magnetically soft mean

Answer 9

lose their magnetism really quickly (nickel and iron)

Question 10

what does being magnetically hard mean

Answer 10

lose magnetism slowly (steel)

Question 11

what will the field lines look like in a wire that has a current flowing through it

Answer 11

circles closest together near to the wire as that is where the magnetic field is strongest

Question 12

what is the right hand rule

Answer 12

put right hand into fist where the thumb is pointing up to the current the other fingers will show the direction of the magnetic field

Question 13

what happens to the magnetic fields in a circular coil

Answer 13

they interact and become
stretched out to form ellipses
they then combine and form one magnetic field with a straight line in the middle

Question 14

what is a solenoid

Answer 14

wire coiled up into spiral shape

Question 15

what are the properties of a magnetic field in a solenoid

Answer 15

strong
uniform

Question 16

electromagnets are only magnetic when

Answer 16

current is flowing through a wire

Question 17

how can we reverse the direction of a electromagnet

Answer 17

reverse current

Question 18

what are 4 ways to increase the strength of an electromagnet

Answer 18

increase current
increase number of coils (length the same)
decrease length(coils the same)
add iron core to solenoid

Question 19

why does decreasing the length of a solenoid and increasing the number of coils increase the strength of a electromagnet

Answer 19

densely packed coils

Question 20

why does adding an iron core increase the strength of a electromagnet

Answer 20

as iron is an induced magnet it will increase the magnetic field strength

Question 21

to experience a full force the wire has to be

Answer 21

90 degrees to the magnetic field

Question 22

to experience a slight force the wire has to be

Answer 22

at an angle

Question 23

to experience no force the wire has to be

Answer 23

same direction as the magnetic field

Question 24

what happens to a coil in an electric motor

Answer 24

spin 180 and the positive and negative terminals will be switched and also the forces will be switched and the coil will flip back to where it has started

Question 25

what do we have to do to make sure an electric motor turns 360 degrees

Answer 25

change the direction of the current every half turn

Question 26

how do we make sure an electric motor turns 360 degrees

Answer 26

split ring commutator

Question 27

what does a split ring commutator do

Answer 27

swaps the positive and negative connections every half turn so the direction of current also swaps so forces acting on the coil will always be the same

Question 28

how can we increase the speed of rotations in an electric motor

Answer 28

current add more turns to coil increase magnetic flux density(adding stronger magnets)