magngetism & electromagnetic induction

Question 1

what is a magnet ?

Answer 1

magnet is any object that produces a magnetic field

Question 2

in a magnetic field diagram, what do denser lines represent?

Answer 2

The density of the lines represent the magnetic field strength. The dense of the lines, the stronger than magnetic field.

Question 3

Explain the core practical of drawing a magnetic field

Answer 3

A compass always lines up with a magnetic field. When a compass is put near a bar magnet the needle in the compass lines up with its magnetic field, the student then draws a dot where the needle points and moves the magnet to that point. the student then repeats this until they have drawn a magnetic field diagram of the magnetic field, going from the north pole to the south pole.

Question 4

why when you put North Pole and a north pole together do they repel?

Answer 4

Since the magnetic field always goes from the north pole to the south pole, when a north pole and north pole is put together, the magnetic field collides and causes repulsion of
either magnet.

Question 5

What is a magnetic material?

Answer 5

Magnetic material is any object that can be influenced by magnetic fields and has the potential to become a magnet

Question 6

what are four common magnetic elements

Answer 6

Nickel
Iron
Cobalt
Steel

Question 7

what is a permanent magnet?

Answer 7

A permanent magnet is a object that has a magnetic field at all times

Question 8

Give two examples of a permanent magnet

Answer 8

The Earth
A bar magnet.

Question 9

What is an induced magnet?

Answer 9

An induced magnet only has a magnetic field temporarily

Question 10

When is an induced magnet formed?

Answer 10

When put in the presence of a permanent magnet

Question 11

what is the relationship between a permanent magnet and an induced magnet?

Answer 11

They always have a force of attraction between them no matter what

Question 12

what is a magnetically soft material?

Answer 12

A material that loses its magnetism quickly

Question 13

What is a magnetically hard material?

Answer 13

A material that loses its magnetism slowly

Question 14

what is an electromagnetism?

Answer 14

The phenomenon whereby an electric current produces their own magnetic field

Question 15

Describe the right hand rule for current direction and magnetic field direction

Answer 15

The right hand rule where forming a thumbs up, represents the direction of magnetic field and current. The thumb represents the direction of the current and the curvature of the fingers represents the magnetic field. To find the direction of the magnetic field. You simply point your thumb in the direction of the current.

Question 16

in a circular coil ellipsis occurs. What is this?

Answer 16

in a circular coil, the two magnetic fields going around the coil join together to form another magnetic field going directly down the middle. This is called ellipsis.

Question 17

What is a solenoid?

Answer 17

A solenoid is a wire formed into multiple circular coils

Question 18

Why is a solenoid an electromagnet?

Answer 18

A solenoids and an electromagnet, because the magnetic field is the same as that of a bar magnet. It has a north pole and a south pole and the direction of the magnetic field goes from north to south.

Question 19

What are the four ways of increasing the electromagnetic strength in a solenoid?

Answer 19

1. increased current
   2.increased number of coils
2. decreased length, but the same number of coils
3. Adding an iron core (induced magnet).

Question 20

what is the motor effect?

Answer 20

A current carrying wire in the presence of a magnetic field, will experience a force

Question 21

when does the wire with a magnetic field experience full force when in the presence of another magnetic field?

Answer 21

When at 90° angle to the magnetic field

Question 22

when will the wire with a magnetic field experience no force when in the presence of another magnetic field.

Answer 22

When the wire is going in the same direction as the magnetic field

Question 23

describe Flemings, left-hand rule

Answer 23

flemings left-hand rule, describes the force and the direction of the force in which an object is pushed when, in the presence of a magnetic field, whilst that object has a magnetic field of its own. In Flemmings left-hand roll, the thumb is facing upward. The index finger is facing in an adjacent angle to the thumb and the middle finger is facing towards you. The thumb represents the direction of the force. The index finger represents the direction of the magnetic field. The middle finger represents the direction of the current.

Question 24

What is the equation to work out The strength of the force applied to an object due to the motor effect

Answer 24

Force = magnetic flux density x current x length of wire

Question 25

What is the units for magnetic flux density?

Answer 25

Tesla

Question 26

what are the units for current?

Answer 26

Amps

Question 27

What is the unit for the length of the wire?

Answer 27

Metres

Question 28

because of Flemmings, left-hand rule, when two wires are connected together, what happens to the wire in a magnetic field?

Answer 28

The wire turns 180° and the direction of the forces swap

Question 29

how do you turn The joint wire in a magnetic field 360°

Answer 29

To turn the joint wire, 360°. You have to add a split ring commutator.

Question 30

what is the role of a split ring commutator?

Answer 30

The split ring commutator swaps the positive and negative connections every half turn which changes the direction of current every half turn.
this allows the joint wire to spin 360° over and over until the current is taken away

Question 31

What ways can we increase the speed of the joint wires in a magnetic field?

Answer 31

. Increase the speed.
. Add more turns to the coils.
. Use a stronger magnet.

Question 32

What is electromagnetic induction?

Answer 32

electromagnetic induction is moving, a coil up and down when wrapped around a magnetic field to induce a potential difference (voltage)

Question 33

what in terms of potential difference happens when a change in direction occurs between a magnetic field?

Answer 33

When the direction is changed, the potential difference swaps. if the coil is closed and makes a circuit, then the current created changes direction.

Question 34

What three ways are there to change the size of the induced potential difference or current?

Answer 34

. Change strength in magnet
. Move the wire quicker
. Create more turns on the coil.

Question 35

why in electromagnetic induction does the potential difference disappear when the wire stops moving?

Answer 35

Because the potential difference occurs when a change in magnetic field occurs. Therefore, when the wire stops moving there is no change in magnetic fields and therefore no potential difference and therefore no current

Question 36

what is a transformer?

Answer 36

A transformer is used to increase or decrease a potential difference

Question 37

explain the process of how a transformer works

Answer 37

An alternating potential difference passes through the primary coil. Since this is a closed circuit, this potential difference causes a current to flow which is also alternating and therefore causes an alternating magnetic field around the primary coil. Since the iron core is a magnetic material, the magnetic field around the coil causes this iron to become an induced magnet. Because of the magnetic field around the iron core, the secondary coil induces a potential difference and causes a current to flow.

Question 38

what is a step up transformer?

Answer 38

A step up transformer has more coils on its secondary coil to increases the input potential difference

Question 39

what is a step down transformer

Answer 39

A step down transformer has less coils on the secondary coil to decrease the input potential difference

Question 40

State the two equations used to work out the final potential difference or current on the secondary coil.

Answer 40

Vp / Vs = Np / Ns
Vp x Ip = Vs x Is