P4

Question 1

Where is the force of magnetism strongest on a magnet?

Answer 1

The force of magnetism on a magnet is strongest at the north and south poles

Question 2

Which are the three magnetic materials

Answer 2

Iron, cobalt and nickel are the three magnetic materials

Question 3

Give the definition of a magnetic field

Answer 3

A magnetic field is the region around a magnet where another magnet/ magnetic material will experience a force

Question 4

Which way do field line arrows point?

Answer 4

Field line arrows always point north to south

Question 5

What happens when you place two permanent magnets with opposite poles next to each other

Answer 5

Two permanent magnets with opposite poles create a uniform field

Question 6

What are magnetic field lines used for?

Answer 6

Magnetic field lines are used to show the size and direction of a magnetic field

Question 7

What is the strength of a magnetic field called?

Answer 7

The strength of a magnetic field is called magnetic flux density and is measured in teslas (T)

Question 8

Finish the sentence

Like poles…

Answer 8

Like poles repel

Question 9

Finish the sentence

Opposite poles…

Answer 9

Opposite poles attract

Question 10

Finish the sentence

Both poles attract…

Answer 10

Both poles attract non magnetic materials

Question 11

What will happen to a magnetic material when brought near a permanent magnet?

Answer 11

The magnetic material will become an induced magnet. Most induced magnets will lose their magnetism when moved away

Question 12

Give two ways we can see magnetic field lines in the lab

Answer 12

One way we can see magnetic field lines in the lab is through putting the magnet under a piece of paper and scarring iron filings over which will align themselves with the field lines

Am alternative way of seeing field lines in using a compass. Put a compass next to a magnet and Mark either end of the needles. Move it to the tip and Mark the tip again and repeat to form field lines

Question 13

What is electromagnetism

Answer 13

Electromagnetism is the basis that when an electric current flows through a material and magnetic field is created around it

Question 14

What are the magnetic fields around a straight current carrying wire made up of?

Answer 14

The magnetic fields around a straight current carrying wire are concentric circles

Question 15

How can we find the direction of the magnetic field lines around a straight current carrying wire?

Answer 15

To find the direction of the field Lines around a straight current carrying wire we can use the right-hand rule

Question 16

How can we prove that current creates a magnetic field

Answer 16

We can prove the current creates a magnetic field by using a compass which will point North when turned off but will deflect when turned on

Question 17

What’s the magnetic fields around the flat circular current carrying coil made up of

Answer 17

The magnetic fields around a flat circular current carrying coils are made up of concentric elipses

Question 18

What is a solenoid

Answer 18

A solenoid is a coil of wire acting as a magnet when carrying a current-it is an electromagnet.

Question 19

How can we increase the magnetic effects of the north and south pole of a solenoid?

Answer 19

We can increase the magnetic effects of a solenoid north and South Pole by:

1) increasing the current
2) increasing the number of coils (but length stays the same)
3) decreasing length (but number of could stays the same)
4) decreasing cross sectional area
5) adding an iron core

Question 20

What is the motor effect

Answer 20

The motor effect is when a current carrying wire is put at 90 degrees between two magnetic poles the wire will experience a force

Question 21

How can you determine the direction of the force produced by the motor effect

Answer 21

To determine the direction of the force produced by the motor effect use Flemings left hand rule

1) put your first finger in the direction of the magnetic field
2) put your second finger in the direction of the current
3) your thumb will point in the direction of the force

Question 22

How does an electric motor work?

Answer 22

A loop of current carrying wire is put between two magnetic poles using Fleming‘s left-hand rule one side of the wire experience as an upward force and one side experiences a downwards so the loop rotate 90°. The split ring commutator switch is the direction of the current when the loop hits 90° To keep the loop rotating.

Question 23

How does a loudspeaker work?

Answer 23

1) A coil of wire is wrapped around the end of a cone
2) The coil is connected to an AC power supply
3) A permanent magnet is placed inside the coil
4) When turned on the current passing through the coil creates a magnetic field
5) The magnetic field interacts with the magnetic field of the magnet creating a force causing the cone to move
6) when the AC supply switches force moves in the opposite direction
7) The constant changing of the force causes the cone to vibrate creating sound waves

Question 24

Definition of electromagnetic induction

Answer 24

electromagnetic induction is the production of voltage across the conductor due to a change in its external magnetic field

Question 25

Explain using examples how the generator effect works

Answer 25

if we were to move a piece of wire through a magnetic field a potential difference will be induced along the ends of the wire we moved in the opposite direction the potential difference has reversed direction. If we were to move a complete circuit through a magnetic field we would induce current the direction of the current would also switch from the direction of movement switches

Question 26

What is an alternator

Answer 26

alternator is a coil of wire/magnet rotating magnetic field to produce an alternating-current based on the generator affect

Question 27

How does an alternate to produce an alternating-current ?

Answer 27

Alternator uses slip rings which don't swap every half turn this means that the potential difference is reversed every turn producing and alternating-current .

Question 28

What is the Dynamo ?

Answer 28

Dynamo is a coil of wire rotating in a magnetic field to produce a direct current based on the generator effects

Question 29

How does a Dynamo produce a direct current ?

Answer 29

Dynamo produces a direct current three using a split ring commutator which swaps the connection every half turn to keep the current flowing one way.

Question 30

Explain how the microphone works

Answer 30

The microphone consist of a magnet attached to a coil of wire which is attached to an alternating-current attached to a piece of plastic called the diaphragm. When soundwaves hit the diaphragm they cause it to vibrate this causes the wire to move in and out of the magnetic field this induces a potential difference across the ends of the wire and the potential difference is passed through an amplifier to loudspeaker.

Question 31

What is a transformer ?

Answer 31

Transformer is an appliance that changes the size of the potential difference of an alternating-current

Question 32

Explain what a step up transformer is

Answer 32

a step up transformer is appliance which increases the potential difference of alternating-current. And alternating-current is attached to a coil of wire wrapped around an iron core as a current flows through the primary coil it generates a changing magnetic field this magnetic field transmitted along the broken core and through to a secondary coil of wire which induces a potential difference of the secondary coil . The potential difference produced in the secondary coil is greater than a primary coil in a step up transformer because the number of turns in secondary coil is greater .

Question 33

Explain what is stepdown transformer is

Answer 33

A step down transformer is an appliance that decreases the potential difference of an alternating-current. A primary coil wrapped around an iron core is attached to alternating-current as the current flows to the primary call it generate the change in magnetic field this magnetic field is transmitted along the iron core to a secondary coil which induces a potential difference . The potential difference induce second coil is less then at the primary coil as there is less number of turns.

Question 34

Potential difference across primary coil /potential difference across secondary coil=

Answer 34

Number of turns in primary core/number of turns on secondary coil