Topic 1 - Energy - 1.2-Conservation and Dissipation of Energy

Question 1

State the law of energy conservation.

Answer 1

Energy cannot be created or destroyed
(it can only be transferred into different
forms).

Question 2

State any changes in the total energy of
a ball that is kicked, assuming that no
external forces act.

Answer 2

The total energy of the system remains
constant due to the conservation of
energy.

Question 3

What is waste energy?

Answer 3

The energy that is not used by the device
for its desired purpose.

Question 4

Describe the energy changes that occur
in a filament light-bulb.

Answer 4

●Electrical energy is transferred into
light and heat energy
●Light is a useful energy form, heat is
waste energy

Question 5

State two equations to calculate
efficiency.

Answer 5

=Useful Output Energy Transfer/Total
Input Energy Transfer
=Useful Power Output/Total Power
Output

Question 6

How can the efficiency of a system be
increased?

Answer 6

1. Reducing waste output (by
   lubrication, thermal insulation etc.)
2. Recycling waste output (eg. recycling
   thermal waste energy as input energy)

Question 7

State the consequence for energy
transfer of a material with a high thermal
conductivity.

Answer 7

The rate of energy transfer through the
material is higher than for a material with
a lower thermal conductivity.

Question 8

Do double-glazed windows have a
higher or lower thermal conductivity than
single-glazed windows?

Answer 8

Lower, meaning less energy transfers
through them.

Question 9

What key factors affect the rate of
cooling of a building?

Answer 9

●The thickness of the walls

●The thermal conductivity of the walls

Question 10

State three methods of reducing heat
loss in a building.

Answer 10

1. Double glazing
2. Loft and wall insulation
3. Thicker walls