Can be transferred by
conduction, convection,
or radiation
Infrared radiation
Electromagnetic waves
Dark matt surfaces absorb and emit information best
Shiny silver surfaces best reflect heat
All objects absorb
and emit radiation
Rate of heat transfer
depends on surface
area
Specific heat capacity
Energy (E in Joules)= Mass (M in kg) x Specific Heat
Capacity (J/kgC) x Temperature change (theta)
Types of energy
Electrical
Light Sound
Kinetic
Nuclear
Thermal
Gravitational
Elastic
Chemical
The last three
are forms of
stored energy
Conduction, Convection and Radiation
Conduction
Kinetic theory explains the 3 states of matter (solid, liquid, gas)
Solid- strong forces of attraction,
not much energy so can only vibrate
around fixed positions
Liquid- weaker forces of attraction,
mcan form irregular arrangements,
more energy so can move in random
directions at low speeds
Gases-No attraction between the particles, and the
most energy, and are free to move at high speeds
Mainly in solids.
Extra kinetic energy turns into heat
Best in metals because of free electrons
Convection
Liquids and gases only
Circle of heating, travelling then cooling
Heat radiation infrared energy
Bigger surface area, more infrared waves can be emmitted
Energy Transfer
Condensation and evaporation
When a gas cools and lose kinetic energy
If it gets close enough the gas becomes a liquid
Vice versa for evaporation
The rate of evaporation is best due to high temperatures,
low density, larger surface area, and high airflow
Electricity
Cost of Electricity
Energy= Power x time
kWh=Kilowatt-hours
Total energy from two metre
readings= subtract the smaller
from the end
Electrical Appliances
Which one is more cost
effective or uses less energy
Standard of living is affected by access to electricity
Energy and the Environment
Renewable energy
Wind power- turbines create no pollution, very
noisy, rely on wind, high initial cost but no
running costs and no permanent damage
Solar Cells- No pollution, but some to create them,
very reliable during the day in sunny countries, high
initial costs, Expensive to connect to the national grid
Hydroelectric is is used in dams and falling water- expensive and difficult to
build, reliable, cheap to connect to the national grid, loss of habitats
Pumped storage is used to save energy
Geothermal and biofuel use heat
Non renewable energy
Creates CO2 through combustion, sulphur
dioxide causing acid rain, nuclear waste is
dangerous
Comparisons
Initial costs, reliability
issues, environmental
issues, set
up/decommissioning
time, running costs,
location issues
National Grid
Current creates heat so a step
up/step down increases voltage to
decrease current and vice versa
How electricity is transferred
Waves
Basics
Waves have amplitude- height from the middle, wavelength,
which is from crest to crest, or frequency in Hz
Transverse waves have sideways vibrations
Longitudinal waves are along the same lines
Wave Speed (m/s)= Frequency (Hz) x Wavelength (m)
Refraction + Diffraction
Diffraction - waves spreading out.
When a gap is the same size as wavelength= maximum diffraction
Refraction- changing speed changes direction
Crossing a boundary between 2 substances EG glass to air