Magnetism and the Electromagnetism

Question 1

what is a magnetic field

Answer 1

the region around a magnet where other magnets experience a non-contact force acting on them

Question 2

what do permanent magnets do

Answer 2

produce their own magnetic field all the time

Question 3

what do induced magnets do

Answer 3

they create a magnetic field when they’re in another external magnetic field

Question 4

what happens when an external field is removed

Answer 4

magnetism is mostly lost

Question 5

what are magnets made of

Answer 5

magnetic materials such as iron, nickel and cobalt

Question 6

what determines how quickly magnetism is lost

Answer 6

the ‘softness’ of the material

Question 7

why are permanent magnets made out of steel

Answer 7

they are magnetically ‘hard’ as they take long time to lose magnetism

Question 8

what is the needle in a compass

Answer 8

a small bar magnet which always points in the direction of the magnetic field it is in

Question 9

how do you find the shape of a magnetic field

Answer 9

1. Put the magnet on paper and draw around it
2. Put the compass near the magnet on paper and mark the direction of the compass with one dot at each end of the needle
3. Move the compass so the needle south is at north dot and then repeat step 2
4. Repeat step 3 all around the magnet and join the points

Question 10

what direction does a compass, when it is not near a magnet, point

Answer 10

North

Question 11

why does a compass, when it is not near a magnet, point North

Answer 11

because it is attracted to the magnetic field of the Earth

Question 12

what happens when a current flows through a conductor

Answer 12

a magnetic field is created around it in concentric circles perpendicular to the conductor

Question 13

what is the right hand thumb rule

Answer 13

point your right hands’ thumb in the direction of the current and curl your fingers. The direction of your fingers is the direction of the field

Question 14

what happens to the strength of the magnetic field when there is a larger current or its closer to the wire

Answer 14

stronger magnetic field

Question 15

what is a solenoid

Answer 15

a coil of wire used in the construction of electromagnets

Question 16

what happens to the field lines in solenoids

Answer 16

field lines around each loop of wire line up with each other

Question 17

what happens in solenoids when the wire’s wrapped into multiple loops

Answer 17

the field lines overlap and interact

Question 18

what happens inside solenoids

Answer 18

field lines point in the same direction and magnetic field lines are strong, almost uniform

Question 19

what happens outside solenoid

Answer 19

overlapping field lines cancel out, point in different directions so break apart from the ends of solenoid

Question 20

how do you increase the strength

Answer 20

more turns
add an iron core
increase the current

Question 21

what are magnets used for

Answer 21

the force of attraction between two magnets used to keep fridge doors closed

magnets are are used to make magnetic separators, used in recycling plants to sort metal items

Question 22

what is the motor effect

Answer 22

when interacting magnetic fields around two separate objects results in the movement of one of the objects

Question 23

how do you increase the force

Answer 23

increase the strength of magnetic field or use higher current

Question 24

force =

Answer 24

magnetic flux density x length of wire x current

Question 25

what is flemings left hand rule

Answer 25

current must be flowing perpendicular to magnetic field

thumb = direction of force
index finger = magnetic field direction
second finger = direction of current