Wh Y9 HT 1 Flashcards
Magnetic field
A region magnetic objects have around them where the magnetic force can be felt.
The 3 magnetic elements at room temperature:
Iron(Fe)
Nickel(Ni)
Cobalt(Co)
Steel is made of what
C + Fe
What does sulphur do when bound with iron
Removes its magnetism as it becomes iron sulphide
North Pole on a magnet:
North seeking
South Pole on a magnet:
South seeking
North and south poles can __________…
Interact with eachother or put force on eachother
Like poles
Repel
Unlike poles
Attract
The arrows on a magnetic field bar magnet diagram show what
The force feels if another North Pole was there
When two north poles are next to eachother in the centre is
A neutral point of no magnetic force due to the fields cancelling eachother out (destructive interference)
When a north and a South Pole are next to eachother
Lots of parallel lines of flux so high flux density so the field strength is strong. It is also constant
Why does the earth have its own magnetic field?
Because the core is made of iron
Where is the earths magnetic field weakest
Along the equator
The earths magnetic field does what to protect us from the sun
It deflects the suns’ rays
What can an EM do that a normal magnet can’t?
Have its magnetism switched on or off
How to make an EM
Soft magnetic core (soft iron/pure iron)
Wrapped in current carrying wire to create and EM
Another name for an EM
A solenoid
How to turn an EM on
Apply DC current through the coil. This aligns the domains
How to turn an EM off
You can’t just turn off the DC current as there will still be residual magnetism so we apply AC current to unaligned the domains and demagnetise it
How to increase an EM’s strength
More coils per unit length
Increase current input
Choose a core with a higher permeance
Permeance
The ability of an object to accept or amplify a magnetic field
How many times does AC current change direction from the plugs?
About 50 times per second, 50Hz
Uses of an EM
Electric doors Fire bells Train joins Hover boards MRI scans DC motors Generators Speakers Doorbells
Motors’ energy transfer:
El to ke
How does a DC motor work
See book for diagram etc.
How to reverse the spin of a DC motor
Make the current flow in the opposite direction round the circuit
Or reverse the permanent magnet
Graph- physics
Title- A graph showing the …
X axis- independent
Y axis- dependant
Increase the rate of spin for a DC motor
Increase the voltage which increases the current which increases the magnetic field which increases the forces and therefore makes it spin faster
Another name for a generator
A dynamo
Generator energy transfer
Ke to EL
Generator can be described as what
A motor in reverse
Electromagnetic induction
process of moving a magnet into a coil of wire to produce a volatage
Faraday’s law
States that potential difference is induced across a wire producing electric current when a coil of current carryon wire cuts through a magnetic field or a magnetic field is cut through a coil of wire
To increase induced voltage
Increase spin speed
Increase coils per unit length
Hydro
Situated in rivers. Water flows downstream pushed through the dam and spins turbines
maximises on GPE
GPE ke el
Tidal
Tidal barrage- Dam structure created sea tide passes under it and sound turbines
Gpe ke el
Wind
Onshore and offshore
Wind turns big turbine
Ke el
Nuclear
235 uranium or 239 plutonium nuclei absorb a neutron setting off a chain reaction of the nuclei splitting 3 neutrons being released and energy being released. The thermal energy heats up water and turns to gas which spins a turbine
Nu th ke el
Geo thermal
In volcanic active areas hot rocks under the crust. When they decay steam rises and spins turbines else water poured down and is heated and turned into steam
Th ke el
Wave
The movement of seawater in and out of a cavity on the shore compresses trapped air, driving a turbine.
Ke el
Biomass
Burning dead organic matter (wood, ethanol, plants etc.)
Th el
Solar
Photovoltaic cells light energy is absorbed by the pc cells. Uses difference in conductivity between the silicon in it to generate a voltage
Solar power tower- light and heat from the sun is reflected from the mirrors up to a solar collector. Heat boils water etc. Nuc th ke el
Sankey diagrams show what
Energy transfers useful and wasted energy
Sankey diagrams’ thickness shows
The amount of energy
Kettles waste little amounts of energy because
Insulated
Anchored base to stop movement
Energy =
kWh
Power x time
kW. Hrs
Cost of energy =
p
Energy used x cost per kWh
kWh. P/kWh
Filament lamp-
Creates light by pushing current through a wire which gets hot and glows releasing light
Filament
Wire of tungsten
Lamp in circuit
X in a circle
Variable supply (power)
Circle then arrow pointing diagonally up right then circle
Ammeter symbol
A in a circle
Voltmeter symbol
V in a circle
Ohms law
Resistance
Ohms
