1.2 Conservation and Dissipation of Energy Flashcards
State the law of energy conservation.
Energy cannot be created or destroyed
(it can only be transferred into different forms).
State any changes in the total energy of
a ball that is kicked, assuming that no
external forces act.
The total energy of the system remains
constant due to the conservation of
energy
What is waste energy?
The energy that is not used by the device
for its desired purpose.
Describe the energy changes that occur
in a filament light-bulb
● Electrical energy is transferred into
light and heat energy
● Light is a useful energy form, heat is
waste energy
How can the efficiency of a system be increased?
- Reducing waste output
- Recycling waste output
how to reduce waste output
lubrication
insulation
how to recycle waste output
recycling
thermal waste energy as input energy
State the consequence for energy transfer of a material with a high thermal
conductivity.
The rate of energy transfer through the
material is higher than for a material with a lower thermal conductivity.
Do double-glazed windows have a
higher or lower thermal conductivity than single-glazed windows?
Lower, meaning less energy transfers
through them.
What key factors affect the rate of
cooling of a building?
● The thickness of the walls
● The thermal conductivity of the walls
State three methods of reducing heat
loss in a building.
- Double glazing
- Loft and wall insulation
- Thicker walls
How can the efficiency of a mechanical
machine with moving parts be improved?
Lubricate any moving parts to reduce the
friction and therefore energy loss due to
heating
How can the efficiency of a radiator be
improved?
Installing metal foil sheets behind the
radiator to reflect the heat back into the
room rather than it being absorbed into
the walls.
How can the efficiency of boiling water in a pan be
improved?
By placing a lid on the pan to reduce the
heat loss from the top.
