Electromagnetism

Question 1

what are some metals tat are magnetic

Answer 1

Metals that are magnetic are: Iron, nickel, cobalt and steel

Question 2

what are the poles on a magnet

Answer 2

The poles on a magnet are the strongest parts of a magnet

Question 3

what are permanent magnets

Answer 3

Permanent magnets are like the ones which are metal blocks used in school, made from metals like steel
It is called permanent, as they are magnetically hard, meaning once the material is magnetised, it cannot lose its magnetism

Question 4

what are magnetically soft materials mean

Answer 4

Magnetically soft materials are when once the material is magnetised, it will lose its magnetism.
An example of a magnetically soft material is iron - these materials are useful for temporary magnets

Question 5

what is a magnetic field

Answer 5

Magnetic field = volume of space around the magnet where we can detect magnetism

Question 6

where do magnetic fields go from

Answer 6

Magnetic field lines go from north to south,

Question 7

where are the magnetic fields strongest

Answer 7

and they are most dense at the poles since this is where the magnetism is strongest.

Question 8

what do magnetic fields show

Answer 8

The magnetic field lines:
show the shape of the magnetic field
direction - north to south
strength - strongest where the lines are closest together

Question 9

what does uniform magnetic field mean

Answer 9

Uniform magnetic field = (uniform means equal) - When the magnetic field lines are equally spaced, going in the same direction, meaning the magnetic field STRENGTH and DIRECTION is the same everywhere

Question 10

what can inducing magnetism only occur with

Answer 10

Inducing magnetism can only occur with magnetic materials

Question 11

what is induced magnetsm

Answer 11

it becomes a magnet itself - magnetism has been INDUCED in this magnetic material

Question 12

what happes to magneticaly soft/ hard matierals when induced

Answer 12

If a magnetically soft material is used, it will lose its magnetism after a set amount of time
If magnetism is induced in a magnetically hard material, it will retain some of its magnetism, even after the magnet is taken away (even after the magnetically hard material is taken out of the magnetically hard field)

Question 13

what does a uniform magnetic field look like

Answer 13

the lines will be evenly spaced and straight

Question 14

how can a uniform magnetic field be created

Answer 14

A uniform magnetic field can be created using U-shaped magnets

Question 15

what is electromagnetism

Answer 15

Electromagnetism = a magnetic field that is created around a wire, when there is a current running through it

Question 16

how to determine the direction of a magnetic field in a straight current

Answer 16

Use the right hand rule to determine the direction of the field around it

Question 17

how to use the right hand rule

Answer 17

The magnetic field around a wire is in circles, the way rings on your thumb are, with your thumb being the wire. The direction your thumb is pointing is the direction that the current is travelling in. The direction of the magnetic field, follows the path of your fingers when they curl into your palm.

Question 18

what do we call a coiled wire

Answer 18

A coil of wire is called a solenoid

Question 19

The strength of the magnetic field that is created around a current-carrying wire can be increased by: (3)

Answer 19

1. Adding an iron core
2. By increasing the number of coils in the solenoid
3. Increasing the size of the current running through the wire

Question 20

what shape are the magnetic fields of a solenoid relative to a bar magnet

Answer 20

The shape of the magentic field around a solenoid, is the same as that around a bar magnet

Question 21

what is the solenoid rule

Answer 21

The solenoid rule is OPPOSITE to the right hand rule
The way you use your hand is the same, but the role of your thumb, and fingers inverse
With the solenoid rule, your fingers follow the path of the current and your thumb points to north (you can use north to figure out the direction of the magnetic field)

Question 22

when do you use the solenoid rule and right hand rule

Answer 22

With a straight piece of wire, you use the right hand rule, as your thumb is straight, like the wire
With a coiled piece of wire (a solenoid), you use the solenoid rule, as your fingers curl in, like the wire’s coils curl

Question 23

what direction are the magnetic fields in a solenoid

Answer 23

The direction on the magnetic field on the curving magnetic field lines OUTSIDE the solenoid, are opposite to the direction of the straight magnetic field lines inside the solenoid

Question 24

what happens when a charged particle moves through a magnetic field

Answer 24

When a charged particle is moved through a magnetic field, it will experience a force
(If the motion is parallel to the field, then it won’t experience any force - force = 0

Question 25

what is the motor effect

Answer 25

The motor effect = the effect when a current carrying wire is placed in a magnetic field, and the interaction of the two magnetic fields exerts a force on the wire

Question 26

when are forces produced on a wire the greatest by another magnetic field

Answer 26

The force produced on the wire is greatest when the field and current are perpendicular to each other, and zero when they are parallel.

Question 27

Explain flemmings left hand rule

Answer 27

With Fleming’s left hand rule, we can predict the direction of the motion of the wire Use Mama’s Fried Chicken to figure out the fingers: thumb = motion (Mama’s) index finger = field (Fried) middle finger = current (chicken)

Question 28

how does a moving coil loudspeaker work

Answer 28

Moving coil loudspeaker: This is designed to use the motor effect to transfer electrical energy into sound energy

Question 29

describe the flowchart of how a moving coil speaker works (5)

Answer 29

1. Electric currents pass through the coils of the speaker(ac) 2. These currents could be coming from a source, like a radio, and so the currents will represent sounds - this means they will be changing in size and direction (like vibrating sound waves) 3. The changing size and direction of the current, means that the magnetic field patterns will also be changing in size and direction 4. These fields will exert forces on the wire (the motor effect), which causes the speaker cone to vibrate 5. These vibrations create sound waves

Question 30

what is the use of a motor oeffect

Answer 30

A use of the motor effect is an electric motor

Question 31

how does the electric motor work

Answer 31

In our electric motor, there is a loop of wire - when current runs through this wire, one side would begin to feel an upwards force, one side would begin to feel a downwards force, causing the loop to start to turn

Question 32

how does a split ring commutator work

Answer 32

In this electric motor, there is a split-ring commutator, attached to the circuit by carbon brushes Each time the loop of wire turns past the vertical position, the connections change, the direction of the current changes, and the force experienced on each side of the loop changes - this allows our loop to rotate continuously

Question 33

how To increase the rate at which the motor turns (3)

Answer 33

1. increasing the strength of the magnetic field 2. increasing the current in the loop of wire 3. making a coil/increasing the number of loops/coil in a wire

Question 34

what is electromagnetic induction

Answer 34

Electromagnetic induction = using motion to generate electricity

Question 35

how can you generate electricity with a magnetic field

Answer 35

For the highest generation of electricity, the wire should be moved across a magnetic field at right angles OR a magnet moves through a solenoid

Question 36

how can The size of the voltage and current generated whe moving a wire through a magnetic field be increased (3)

Answer 36

1. moving the wire quicker 2. using a coil of wire so more of the wire ‘cuts’ through the magnetic field 3. increasing the strength of the magnetic field so that more field lines are ‘cut’

Question 37

how can The size of the voltage and current generated whe moving a magnet through a solendoid be increased (3)

Answer 37

1. moving the magnet faster 2. increasing strength of magnetic field/using a stronger magnet 3. using a coil with more turns The faster the field lines are cut, the higher the induced voltage/current

Question 38

how does a dynamo work (5)

Answer 38

the magnet is attacked to a poll, at the top of the rod is a round piece of metal acting like a cog the tyre when rotated moves the round peice of metal, rotating the magnet as the magnet rotaties, the magnetic field changes as the north and south polls switch, the magnetic field of the coil is cut, producing electricity this electricity powers the bike light, whenever the person pedals the bike, the light turns on

Question 39

wha affects the brightness of a light when using a dynamo and why

Answer 39

the brightness of the light depends on the amount of force being exerted on pedalling the bike this is due to the poles on the magnet, switching faster, cutting the magnetic field of the coil quicker, generating more power to the light

Question 40

what is a transformer

Answer 40

A transformer changes the size of an alternating voltage - by having a different number of turns on the primary and secondary coils

Question 41

what current can transformers only work with

Answer 41

Transformers only work with alternating currents and pd

Question 42

why does a transformer need the type of current it needs

Answer 42

This is because for our transformer to work, the magnetic field in our primary coil needs to be constantly changing

Question 43

how does the current in the primary coil induce the secondary coil (4)

Answer 43

When we pass a current/pd through our primary coil, this induces a magnetic field around it As the current we use is ac, our magnetic field is going to be constantly changing directions If a second coil is placed near the first, the changing magnetic field cuts through our secondary coil As it cuts through the wires of the secondary coil, a voltage/pd is induced in that coil

Question 44

how will the pd/current induced in the secondary coil change

Answer 44

The size and direction of the voltage induced in the secondary coil will change with any changes we make to the voltage/current supplied to the first coil

Question 45

what is the equation for transformers

Answer 45

Vp/Vs = Np/Ns V= voltage n = number of turns in the p = primary/s = secondary coil

Question 46

what can you do to make the transformer as efficient as possible (2)

Answer 46

1. Thick copper wires are used for the coils 2. The soft iron core is covered in a thin layer of plastic to connect the two coils

Question 47

what are national grids

Answer 47

National Grids = networks of wires and cables that carry electricty from power stations to consumers, like homes, schools, factories etc

Question 48

what is the flowchart of energy in a country

Answer 48

Power plant ⟶ step up transformer ⟶ national grid ⟶ step down transformer ⟶ homes/consumer

Question 49

what do step up transformers do

Answer 49

Step up transformers means that electricity is being transmitted is sent as low current, high voltage

Question 50

why do we use step up transformers

Answer 50

A high current in the wires will mean there is a high resistance, so the wires will heat up and lots of energy will be lost as heat energy So, to transmit electricity as efficiently as possible, current is lowered so that resistance in the wires is minimised

Question 51

why do we use step down transformers

Answer 51

Step down transformers are used to decrease the voltage and increase the current, as a high voltage is dangerous in homes When cables enter towns and cities, they are buried underground