Magnetism and Electromagnetism

Question 1

What do magnetic field lines show us?

Answer 1

The general shape of the field
Direction of field lines, the arrows go from north to south
Strength of the field, closer the line stronger the field

Question 2

Explain what is meant by induced magnetism

Answer 2

An unmagnetised material piece/magnetic metal is placed within a magnetic field it will act as a magnet. But only whilst in the magnetic field.

Question 3

Is it possible for induced magnetism to produce repulsion? Explain why.

Answer 3

No because the induced poles are always in the same order as the first magnet. Hence it is not possible for like poles to be facing each other.

Question 4

What are the three magnetic metals?

Answer 4

Iron, cobalt and nickel

Question 5

What do we mean by magnetically hard and soft materials? Give examples of both.

Answer 5

When the domains are pointing in random direction each little magnetic field cancels out its neighbours and the metal will not be magnetic. When an external magnetic field is applied the domain line up and reinforce each other, meaning magnetism had been induced.
Substances that can be permanently magnetised are described as magnetically hard (steel)
Substances that can only be temporarily magnetised are described as magnetically soft (Iron)

Question 6

What is the motor effect?

Answer 6

When a current carrying wire is placed into a magnetic field in between two magnets , that wire will experience a force (movement), the wire can’t be parallel or no force will be applied

Question 7

FLEMING’S LEFT HAND RULE

Answer 7

A current carrying wire has a magnetic field around it. If this field interacts with an external magnetic field produced by a permanent magnet it will experience a force. The direction of the force is indicated by Fleming’s Left Hand Rule.

-First Finger Field
-seCond finger Current
-thuMb Movement (of force)

Question 8

magnetic force and current

Answer 8

-directly proportional

Question 9

The size of the magnetic force can be increased by doing the following:

Answer 9

-Have a stronger external magnetic field
-Increase the electric current
-Use more coils of wire (if you have a coil)

Question 10

straight wire

Answer 10

• The electric current would produce magnetic field around wire
• The field lines are concentric circles around wire
  -closest together near wire as magnetic field is the strongest
  -the direction of field depends on direction of current (right hand rule, turn hand into first and point your thumb in the direction of current, the direction your fingers are curling is the direction of field lines)

Question 11

flat circular coil

Answer 11

• the magnetic field that were concentric circles turn into elipses
  -also form a single magnetic field that runs straight in between the wire

Question 12

a solenoid

Answer 12

-magnetic field within (in the inside) the solenoid are strong and uniform
- the outside field lines go from the north to the south

Question 13

Electromagnets are only magnetic as long as we keep the current flowing.
True or False

Answer 13

True

Question 14

How to reverse direction of magnetic field in a electromagnet?

Answer 14

reverse the direction of the current

Question 15

How to increase an electromagnets strength?

Answer 15

-add iron core to the inside of the solenoid because iron is a soft material it becomes an induced magnet and strengthens the electromagnets magnetic field

Question 16

LOUDSPEAKER, MOTOR

Answer 16

-An alternating current is fed into a coil, generating an alternating electromagnetic field.
This produces a magnetic force which is continually changing direction
The coil is connected to a cone which will vibrate and produce a sound
-Loudspeakers take electrical signals and use the motor effect to convert them into vibrations, which then generate sound waves.

-temporary magnetic field of the wire interacts with the permanent magnetic field of magnet