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Paper 1
Energy
Conservation and dissipation of energy
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Cards (13)
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
State
two equations to calculate efficiency 

=
Useful output energy
transfer/total input energy transfer
=
useful power output
/total power output
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)
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