Energy Flashcards
What are the eight energy stores?
thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear
How can energy be transferred?
mechanically, electrically, heating, radiation
Describe the energy transfers that occur when the wind causes a windmill to spin.
- energy transferred mechanically
- from kinetic energy store of wind
- to kinetic energy store of windmill
When is energy transferred away the kinetic energy store?
when an object slows down
What does kinetic energy depend on?
mass and speed
What is the formula for kinetic energy?
1/2 x mass x velocity squared
What is the formula for gravitational potential energy?
mass x gravitational field strength x height
What is the formula for elastic potential energy when the limit of proportionality hasn’t been exceeded?
1/2 x spring constant x extension squared
What is specific heat capacity?
amount of energy needed to heat 1kg of a substance by 1’C
What is the formula which includes specific heat capacity?
change in thermal energy = mass x specific heat capacity x temp. change
What is the Conservation of Energy Principal?
energy can be transferred usefully, stored or dissipated, but can never be created or destroyed
What is dissipated energy also known as?
wasted energy
What is power?
the rate of doing work
What is power measured in?
watts
From which equations can you calculate power?
power = energy transferred
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time
power = work done
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timeWhat is a powerful machine?
one which transfers a lot of energy in a short space of time
What is conduction?
vibrating particles transfer energy to neighbouring particles
What is thermal conductivity?
a measure of how quickly energy is transferred through a material by conduction
What is convection?
the energetic particles move away from hotter to cooler regions
How can a convection current be created?
if there is a constant heat source
Does warm air rise or sink?
rise
How can you reduce heat loss in homes?
- thick walls of a material with low thermal conductivity
- thermal insulation
What are the ways of thermally insulating your home?
- cavity walls which are inner and outer wall with air gap in the middle reducing conduction
- loft insulation reducing convection currents in lofts
- double glazed windows reducing conduction
- draught excluders (around doors and windows) reducing convection
How can you improve efficiency of objects?
insulation, lubrication, streamlining
What is the formula for efficiency?
total power input
Explain how a cavity wall insulation reduces the amount of energy transferred out of the house.
- reduces convection
- also reduces conduction
- insulating foam has low thermal conductivity so low rate of energy transfer
