Topic 12: Magnetism and the Motor Effect

Question 1

At which part of a magnet are the magnetic forces strongest?

Answer 1

The poles of the magnet

Question 2

What happens when two magnets are brought close to each other?

Answer 2

The exert a force on each other

Question 3

What type of force is exerted if two like poles of a magnet are brought near each other?

Answer 3

A repulsive, non-contact force

Question 4

What type of force is exerted if two unlike poles of a magnet are brought near each other?

Answer 4

An attractive, non-contact force

Question 5

What is a magnetic field?

Answer 5

The region surrounding a magnetic where another magnet or magnetic material experiences a non-contact force

Question 6

What is the difference between a permanent magnetic and an induced magnet?

Answer 6

A permanent magnet produces its own whereas induced magnet becomes magnetic when placed in a magnetic field

Question 7

What type of force do induced magnets always cause?

Answer 7

A force of attraction

Question 8

What is the effect when an induced magnet is removed from a magnetic field?

Answer 8

The induced magnet loses most/all of its magnetism

Question 9

What are some examples of magnetic materials?

Answer 9

Iron, steel, cobalt and nickel

Question 10

What can always be said about the force between a magnet and a magnetic material?

Answer 10

Always attractive

Question 11

How does the strength of a magnetic field alter as you move further away from the magnet producing it?

Answer 11

The magnetic field strength decreases the further you move away

Question 12

In what direction does a magnetic field point?

Answer 12

In the direction of the force that a North Pole would experience if placed in the field (from the north seeking pole to the south seeking pole of a magnet)

Question 13

What does a magnetic compass contain?

Answer 13

A small bar magnet that points in the direction of the Earths magnetic field

Question 14

What is produced when current flows through a conducting wire?

Answer 14

A magnetic field is produced around the wire

Question 15

What determines the strength of the magnetic field around a current-carrying wire?

Answer 15

The magnet use of the current flowing through the wire

Question 16

Does a high concentration of field lines mean the field is strong or weak?

Answer 16

Strong

Question 17

How is a plotting compass used to map out a magnetic field?

Answer 17

Place a compass on a piece of paper near the field, draw an arrow in the direction the compass point, repeat at different points on the paper and join the arrows to make a complete field pattern

Question 18

What is a solenoid?

Answer 18

A coil of wire which when current passes through relates a strong magnetic field

Question 19

What is the magnetic field found inside a solenoid like?

Answer 19

Strong and unifirm

Question 20

Why is the field outside of a solenoid weak?

Answer 20

The fields from each coil cancel out making the outside fields weak

Question 21

What is an electromagnet?

Answer 21

A solenoid with an added iron core and adding the iron core increases the strength of the magnetic field

Question 22

What is the motor effect?

Answer 22

When a force is exerted between a magnetic field and a current-carrying conductor placed in that field

Question 23

What rule is used to determine the force produced by the motor effect?

Answer 23

Fleming’s Left-Hand Rule

Question 24

When using Flemings left hand rule what does the forefinger represent?

Answer 24

The forefinger points in the direction of the magnetic field

Question 25

When using Flemings left hand rule what does the second finger represent?

Answer 25

The second points in the direction of current flow in the conductor

Question 26

When using Flemings left hand rule what does the thumb represent?

Answer 26

The thumb points in the direction of the force produced by the motor effect

Question 27

What factors affect the size of the force on a current-carrying wire in a magnetic field?

Answer 27

The magnitude of the current flowing through the conductor and the strength of the magnetic field that the conductor is placed in

Question 28

If the direction of current in a current-carrying wire placed in an uniform magnetic field is reversed, what happens to the force?

Answer 28

The direction of the force is reversed

Question 29

If the strength of current in a current-carrying wire placed in an uniform magnetic field is increased, what happens to the force?

Answer 29

The strength of the force is increased

Question 30

What is the equation of force?

Answer 30

Force = magnetic flux density x current x length

Question 31

What criteria must be met for the equation linking force, magnetic flux density, current and length to hold?

Answer 31

The conductor must be at right-angles to the magnetic field it is placed in

Question 32

What is the unit used for magnetic flux density?

Answer 32

Tesla

Question 33

If the current and the magnetic field are parallel to each other, which direction would the force act in?

Answer 33

No force will act

Question 34

How does an electric motor work?

Answer 34

A coil of wire, carrying a current, is placed in a magnetic field, the forces on the two sides perpendicular to the field experience forces in opposite directions and causes a rotational effect

Question 35

How are electric motors kept rotating?

Answer 35

A split ring commutator is used, this switches the current direction every half turn, which ensures that the coil keeps spinning