6.20 know and use the relationship: input power = output power

input power = output power
VP IP = VS IS

(primary voltage x primary current = secondary voltage x secondary current)

This is only true if we assume that something is 100% efficient and has lost no energy in other forms (like heat)

6.19 know and use the relationship between input (primary) and output (secondary) voltages and the turns ratio for a transformer

primary voltage/ secondary voltage = primary turns/ secondary turns

^Vp/_Vs = ^Np/_Ns

6.18 explain the use of step-up and step-down transformers in the largescale generation and transmission of electrical energy

In the national grid (the system which delivers electricity around the country) transformers are used. Because the wires are long there is more resistance, so a high current will cause a lot of heat; which is dangerous and looses a lot of energy. When electricity leaves a power plant, a step up transformer is used, this means the voltage is high, but the current is low. When electricity reaches a home or business it is stepped down to make it useful in appliances that we use, the wires are shorter so less of a danger is presented by this.

bpbtecscience

6.17 describe the structure of a transformer, and understand that a transformer changes the size of an alternating voltage by having different numbers of turns on the input and output sides

A transformer is used to change the current and voltage of electricity.

A current carrying wire is wrapped round one side of a transformer, another wire is wrapped round the other. There will be the same amount of power on both sides, but one will have a higher voltage and lower current the other a lower voltage and a higher current.

The transformer is made of iron, this is because it is a soft metal and can be turned on and off as a magnet: the current from the first wire induces a magnetic field in the transformer, this then induces a current in the second wire.

More coils causes more higher voltage (and lower current.) So if the second side has more turns of wire wrapped round the transformer it will step the voltage up (step up transformer.) If the second side has less turns, the voltage will be stepped down (step down transformer.)

scicenceaid

6.16 describe the generation of electricity by the rotation of a magnet within a coil of wire and of a coil of wire within a magnetic field and describe the factors which affect the size of the induced voltage

rotate a magnet in a coil of wire and there will be a current induced, the same is true for rotating a coil of wire in a magnetic field.

Factors that increase the electricity generated include: strength of magnetic field; number of coils in wire; speed of rotations.

6.15 understand that a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it and describe the factors which affect the size of the induced voltage

If you move a wire back and forth across a magnetic field a voltage will be induced.

If you move a magnet back and forth through a coil of wire a voltage will be induced.

If you increase the magnetic field strength, quicken the movement or increase the coils of wire you can increase the voltage induced!

6.14 describe how the force on a current-carrying conductor in a magnetic field increases with the strength of the field and with the current.

If you have a wire in a magnetic field, if you increase the current there will be more force on the wire; if you increase the strength of the magnetic field there will be more force on the wire.

6.13 use the left hand rule to predict the direction of the resulting force when a wire carries a current perpendicular to a magnetic field

wikipedia

The magnetic field finger is pointing south. The current finger is pointing negative.

6.12 understand that a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers

If there is a wire- with a current running through- in a magnetic field it will experience a force ie it will be pushed up or down.

In a DC motor, there is a wire in a magnetic field. The force it experiences turns it around, this turns a 'split ring commutator' this basically is where charge goes from 'brushes' into the wires. The best way to understand them is with an animation or picture:
http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

hades.mech.northwestern.edu

In a loud speaker, a coil is in a magnetic field. When a current is run through it the wire will experience a force that pushes it away from the field, this in turn pushes a cone which makes the sound. Whatever frequency the AC current is at, the coil will move at that frequency, making a note of a certain pitch.

www.nuffieldfoundation.org

6.11 understand that there is a force on a charged particle when it moves in a magnetic field as long as its motion is not parallel to the field

if something with a charge is moving across a magnetic field, it will experience a force from the field. Unless of course it is parallel in which case it wont need to as it is already in a place the field would want to move it to.

6.10 sketch and recognise magnetic field patterns for a straight wire, a flat circular coil and a solenoid when each is carrying a current

a field around a straight wire is simply a series of circles around the wire.



A field around a solanoid is similar to that of a bar magnet.




A field around a flat coil is basically like a single wire, but there are two.

6.9 describe the construction of electromagnets

A piece of wire is wrapped around a soft magnetic material. When there is a current in the wire, a magnetic field is induced in the metal.

6.8 understand that an electric current in a conductor produces a magnetic field round it

If you run an electric current through anything that conducts (e.g. a wire) a magnetic field will be produced around it!

6.7 describe how to use two permanent magnets to produce a uniform magnetic field pattern.

If you put two bar magnets together with their north and south touching, then they will form the same magnetic field as if there were one bar magnet.

'hold two opposite poles close to each other so that they attract as this makes a uniform magnetic field'

6.6 describe experiments to investigate the magnetic field pattern for a permanent bar magnet and that between two bar magnets

To track field lines you can use iron filings, which are magnetic materials, which will line up along the magnetic field. and you can use compasses which will show that the lines go from north to south. The following results will occur:

6.5 understand that magnetism is induced in some materials when they are placed in a magnetic field

Some materials that are not magnetic can become one when they are in a magnetic field. This is because the magnetic field encourages its electrons to align and form poles. This can happen in iron (and steel), cobalt and nickel.

6.4 understand the term ‘magnetic field line’

Magnetic field lines represent the shape and direction of a magnetic field.
Its important to realise that these lines only represent the field and that the spaces in-between the lines are not in fact spaces in the field, a field is also three dimensional, so the lines just give an idea.

6.3 describe the properties of magnetically hard and soft materials

A magnetically hard material retains its magnetic properties for a long period of time/ permanently  They are hard to demagnetise.

A magnetically soft material looses its magnetic properties almost as soon as it leaves a magnetic field.

6.2 understand that magnets repel and attract other magnets and attract magnetic substances

Opposite poles of magnets attract.
Like poles of magnets repel.
Magnetic substances can also be attracted by a magnet.

6.1 use the following units: ampere (A), volt (V), watt (W)

ampere (A)
volt (V)
watts (W)