Hope they're useful!

HideShow resource information

First 310 words of the document:

Amar Patel
Physics- Energy and Electricity
Heat energy is transferred from high to low temperature. Heat transfer takes place in
three ways:
1) Radiation is energy carried by electromagnetic waves
The sun gives out radiation in all parts of EM waves. Fortunately for us, the Earth's
atmosphere blocks most of the radiation such as UV rays. But it doesn't block thermal
radiation from the sun.
2) Conduction happens in solids, liquids and gases
Metals are good conductors of heats
Poor conductors such as wood and plastic are called thermal insulator.
Conduction in a metal is due to free electrons transferring energy inside the metal.
Materials such as fibreglass are good insulators because they contain pocket of trapped air.
3) Convection only happens in liquids and gases.
Heating a liquid or a gas makes it less dense.
Convection is due to a hot liquid or gas rising.
Convection currents are all about changes in density.
Why do fluids rise when heated?
Most fluids expand when heated. This is because the particles move about more, taking up
more space. Therefore the density decreases because the same mass of fluid occupies a
bigger volume. So heating part of a fluid makes it less dense and it therefore rises.
The thermos Flask
The glass bottle is double-walled with a vacuum between the two walls. This stops all
conduction and convection through the sides.
The walls either side of the vacuum are silvered to keep heat loss by radiation
The bottle is supported using insulating foam. This minimised heat conduction to and
from the outer glass bottle.
The stopper is made of plastic and filled with cork or foam to reduce any heat
conduction through it.

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Amar Patel
Energy Transfer
Energy exists in different forms
Energy can change from one form into another form
Energy cannot be created or destroyed
Nine types of Energy
Electrical Energy- whenever a current flows
Light energy- From the Sun, light bulbs, etc.…read more

Page 3

Preview of page 3

Here's a taster:

Amar Patel
1 kilowatts is equal to 1000 watts
Power (in watts) ­ rate of transfer of energy
A motor transfer 10000J of energy in 25s.…read more

Page 4

Preview of page 4

Here's a taster:

Amar Patel
The National Grid
The National Grid is a network of cables and transformers.
There are four main stages:
1. the fuel is burned to boil water to make
2. the steam makes a turbine spin
3. the spinning turbine turns a generator
which produces electricity
4. the electricity goes to the transformers to
produce the correct voltage
The energy needed to boil the water comes from fossil fuels or nuclear fuels.…read more

Page 5

Preview of page 5

Here's a taster:

Amar Patel
energy transfer diagram for the generation of electricity from a fossil fuel such as coal.
Disadvantages of using fossil fuels
Fossil fuels are non-renewable energy resources. Their supply is limited and they will
eventually run out. Fossil fuels do not renew themselves, while fuels such as wood can be
renewed endlessly.
Fossil fuels release carbon dioxide when they burn, which adds to the greenhouse effect
and increases global warming.…read more

Page 6

Preview of page 6

Here's a taster:

Amar Patel
A wave generator is a floating
generator turning by the waves
Hydroelectricity generators are turned
by water running downhill
A tidal power station traps each high
tide and uses it to turn generators
We can convert solar energy into
electricity using solar cells or use it to
heat water directly in solar heating
Geothermal energy comes from the
Energy released by radioactive
Substance deep inside the Earth
Electromagnetic Waves
Electromagnetic waves are electric and magnetic disturbances that transfer energy from
one place…read more

Page 7

Preview of page 7

Here's a taster:

Amar Patel
Wavelength is the distance
from one peak to the next.
Frequency is how many
complete waves. It's
measured in hertz. (1 Hz is 1
wave length). All
electromagnetic waves travel
through space at a speed of
300 million m/s. All the
different types of
electromagnetic wave travel at
the same speed in a vacuum.
EM waves with high
frequency have lower
wavelengths.…read more

Page 8

Preview of page 8

Here's a taster:

Amar Patel
Short-wave radio signals (TV and FM radio) can, like long waves, be received at long distance
from the Transmitter. That's because they are reflected from the ionosphere ­ an
electrically charged layer in the Earth's upper atmosphere.
Microwaves are used for satellite communication and heating food in microwaves oven.
Microwave radiation has lower frequencies and longer wavelengths than visible light.
Microwaves with certain wavelengths are absorbed by water molecules and can be used for
cooking.…read more

Page 9

Preview of page 9

Here's a taster:

Amar Patel
security pens
fluorescent lights
X-rays mostly pass through skin and soft tissue, but they do not easily pass through bone
or metal. Radiographers in hospitals take X-rays photographs to help doctors diagnose
broken bones, X-rays can cause mutation which lead to cancer. Low doses cause cell
mutation and cancerous growth. Radiographers wear lead aprons and stand behind a lead
screen or leave the room to minimise their exposure to X-rays. High doses kill living cells.…read more

Page 10

Preview of page 10

Here's a taster:

Amar Patel
Isotopes are atoms with different numbers of neutrons. E.g. The carbon-14 has two
more neutrons that `normal' carbon -12
Usually element only has one or two stable isotopes ­ like carbon -12. The other isotopes
tend to be radioactive- the nucleus is unstable, so it decays and emits radiation. Carbon-14 is
an unstable isotope of carbon.
A radioactive substance contains unstable
nuclei. An unstable nucleus becomes stable
by emitting radiation.…read more



Thank-you x

Similar Science resources:

See all Science resources »See all resources »