Conservation and dissipation of energy

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 the 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 lightbulb

• Electrical energy is transferred into light and a heat energy

• Light is useful energy form heat is waste energy

State two equation to calculate efficiency

= useful output energy transfer divided by total input energy transfer

= useful output energy divided by total power input

How can efficiency of system be increased?

• reducing waste output  (by lubrication thermal insulation, etc)

• recycling waste output (e.g. recycling thermal waste energy as input energy)

state a consequence for energy transfer of a material with high thermal conductivity

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

do double glaze windows have higher or lower thermal conductivity than single glazed windows

Lower meaning less energy transferred through them

What key factor affects cooling of a building rate

• The thickness of the walls

• The thermal conductivity of the walls

State three methods of reducing heat loss in buildings?

double glazing loft and wall insulation and thicker walls