P2 - Sustainable Energy Flashcards
In which different forms can energy be
stored?
Chemical, nuclear, kinetic, gravitational,
elastic, thermal, electrostatic and
electromagnetic.
How is energy transferred from one form
to another?
By working or heating.
What form of energy is stored in
batteries?
Chemical energy.
How are electrical appliances supplied
with energy?
Chemical potential in batteries or fuels is transferred to electrical energy (producing electrical current) in wires, which do work on devices such as motors and heaters.
Why is electricity a convenient way to
transfer energy?
It is easily transmitted across large
distances, and can be used to do work in
a variety of ways
What is the principle of conservation of
energy?
Energy cannot be created or destroyed;
it can only be transferred from one form
into another.
How and why is energy wasted?
When energy is used to do work, energy is
dissipated into forms other than the desired
outcome. For example, light bulbs sometimes
emit heat energy. It is dissipated into the
surroundings, into inaccessible thermal stores.
What is the power of an appliance?
A measure of the amount of energy it
transfers per second (i.e. its rate of
energy transfer).
What is the unit of power?
Watt (W)
This is equivalent to 1 Joule per second
(J/s).
What is the equation for power?
Power = energy ÷ time
What is a system?
An object or group of objects.
What is a closed system?
A closed system is one in which no
energy is transferred into or out of the
system. There is no net change to the
energy of the system.
How can “wasted” (thermal) energy be
reduced?
Thermal insulation prevents thermal
energy from being lost from a system.
An example of this is double glazing in
houses, to conserve energy produced by
heating appliances.
How can “wasted” energy in a motor be
reduced?
Lubrication; applying oil to a motor
reduces friction so less energy is lost
overcoming friction.
What is thermal conductivity?
A measure of a material/object’s ability to
conduct heat.
What does a high thermal conductivity
mean?
The higher the thermal conductivity, the more easily heat is transmitted through the material. This results in a higher rate of energy transfer via conduction across the material.
How does thermal conductivity apply to
buildings?
The lower the thermal conductivity of the walls, the less easily heat is lost. Insulating materials are useful as they have a low thermal conductivity, so they retain heat and therefore conserve
energy.
What is efficiency?
The ratio of useful work done to energy supplied. It is often given as a percentage, i.e. the percentage of energy which is converted to a useful form.
Give the equation for efficiency
Efficiency =
Useful energy output / Total energy input
You can convert this to a percentage by
multiplying the answer by 100
How can the efficiency of a system be
increased?
- Reducing waste output (by lubrication,
thermal insulation etc). - Recycling waste output (eg. recycling
thermal waste energy as input energy).
Name a diagram used to illustrate
energy transfers
Sankey diagram
What does a Sankey diagram show?
All of the energy transfers in a system,
including energy wasted/dissipated to
surroundings.
How is a Sankey diagram useful?
It can be used to calculate the efficiency
of energy transfers.
Describe the features of a Sankey
diagram
● Arrows point in the direction of transfer of energy. ● The width of lines/arrows is proportional to the amount of energy transferred.
