Topic 12 - Magnetism and the motor effect

Question 1

All magnets have two

Answer 1

Poles

Question 2

Two poles of magnets

Answer 2

Norht and south

Question 3

Magnets produce

Answer 3

Magnetic fields where other magnets or magnetic materials experience a force

Question 4

Unlike magnetic fields

Answer 4

Attract

Question 5

Like magnetic fields

Answer 5

Repel

Question 6

Magnetic fields can be shown by drawing

Answer 6

Field lines

Question 7

Magnetic field lines rules

Answer 7

Always north to south
Closer the lines, stronger the magnetic field

Question 8

The magnetic forces are strongest at the

Answer 8

Poles

Question 9

When a north and south pole are placed near eachother

Answer 9

A uniform field is created where the magnetic field strength is the same everywhere between the poles

Question 10

Compasses show magnetic field because

Answer 10

They have magnets inside that always line up with the magnetic field its in.
If the way the compass faces is plotted around a magnet, the magnetic field direction can be plotted

Question 11

When not near a magnet, compasses always

Answer 11

Point towards the earths north pole because the earth creates it own magentic field.(north poleis actually the magnetic south pole)

Question 12

Compasses show that the earths core is

Answer 12

Magnetic

Question 13

Main three magnetic elements are

Answer 13

Iron, nickel, cobalt

Question 14

The magnetic force between a magnet and magnetic material is

Answer 14

Always attractive

Question 15

Permanent magnets are

Answer 15

Objects that always produce their own magnetic field

Question 16

Induced magnets are

Answer 16

Objects that only produce a magnetic field when in another magnetic field

Question 17

Magnetically soft materials are

Answer 17

Induced magnets that lsoe their magnetism quickly after being out of a magnetic field

Question 18

Magnetically hard materials are

Answer 18

Objects tat lose their magnetism slowly

Question 19

When a current flows through a long straight conductor

Answer 19

A magnetic field is created around it

Question 20

The magnetic field induced by a current is

Answer 20

Made up of circles perpendicular to the wire

Question 21

Rule to fidn magentic field direction from current

Answer 21

Right hand thumb rule
Direction of current is direction of thumb
Fingers curled in magnetic field direction

Question 22

The strength of current induced magnetic field is dependant on

Answer 22

The current travelling through the wire, and the distance from wire

Question 23

A solenoid is

Answer 23

A long coil of wire with lots of loops

Question 24

The fields from individual coils in solenoids

Answer 24

Add together to form a very strong almost uniform field inside the solenoid
Cancel out to give a weaker field outside the solenoid

Question 25

A solenoid is an example of an

Answer 25

Electromagnet. because it forms a field similar to a bar magnet, and can be turned on and off with current

Question 26

When a current carrying conductor is placed near a magnet

Answer 26

It experiences a force and an equal and opposite force is exerted on the magnet

Question 27

For a wire to experience the full force in a magnetic field

Answer 27

It needs to be 90*

Question 28

The rule that shows current, magnetic field and force when a wire is interactign with a magnet

Answer 28

Flemings left hand rule Thumb facing up shows current direction Fisrt finger right shows magnetic field Second finger facing towards you shows force on current carrying conductor(eg wire)

Question 29

Force(N) =

Answer 29

Magnetic flux density x Current(A) x Length of wire(m)

Question 30

A simple dc motor works by

Answer 30

Having two magnetic poles and a coil fo wire between them. A force is exerted on the opposite side of coil so it spins A split ring commutator is used to ensure the coil keeps spinning, because if there wasnt a change in charge travelling through, the forces would keep swapping and it wouldnt spin