P1 - Conservation and Dissipation of Energy Flashcards
What is conservation of energy?
energy cannot be created or destroyed
What is dissipated energy?
the energy that is not usefully transferred and stored in less useful ways
What is efficiency?
useful energy transferred by a device / total energy supplied to the device
What is elastic potential energy?
energy stored in an elastic object as a result of it being deformed. For example, a stretched spring
What is Hooke’s law?
the extension of a spring is directly proportional to the force applied, as long as its limit of proportionality is not exceeded
What is input energy?
energy supplied to a device
What is power?
the energy transformed or transferred per second. The unit of power is the watt (W)
What is spring constant?
force per unit extension of a spring
What is useful energy?
energy transferred to where it is wanted in the way that is wanted
What is wasted energy?
energy that is not usefully transferred
What is work?
the energy transferred by a force. Work done (joules, J) = force (newtons, N) x distance moved in the direction of the force (metres, m)
What are all the 7 energy stores?
Kinetic, Chemical, Gravitational, Elastic, Thermal, Magnetic, Nuclear
Where is a kinetic energy store?
In a moving object
Where is a chemical energy store?
Chemical energy is stored in the bonds that connect atoms with other atoms and molecules with other molecules
Where is a gravitational energy store?
an object above ground
Where is an elastic energy store?
a stretched or squashed object
What is a thermal energy store?
due to a substances temperature
What is a magnetic energy store?
The energy stored when repelling poles have been pushed closer together or when attracting poles have been pulled further apart
What is a nuclear store?
energy stored in the nucleus of an atom
What are all the energy transfer pathways?
Mechanically, Electrically, by Heating and by Radiation
What is mechanical energy transfer?
When a force acts and energy is transferred
What is electrical energy transfer?
When a current flows
What is energy transfer by heating?
Due to temperature difference
What is energy transfer by radiation?
A wave such as light, microwaves or sound
What is the equation for Gravitational Potential Energy?
ΔEp = mass (m) x gravitational field strength (g) x change in height (Δh)
What is the equation for kinetic energy?
Ek = 1/2 x mass (m) x velocity² (v²)
What is the law of conservation of energy?
Energy cannot be created or destroyed
What is an efficient lightbulb?
CFL bulb
What does CFL Bulb stand for?
Compact Fluorescent Light Bulb
What is an inneficient bulb?
A filament light bulb
What is useful energy?
energy transferred to where it is wanted and in the form it is wanted
What is wasted energy?
Energy that is not usefully transferred
What is the equation for efficiency?
Efficiency % = (Useful energy out/total energy in) x 100
What is the equation for Elastic Potential Energy?
Ee = 1/2 x spring constant (k) x extension² (e²)
What is the unit of measurement for Work Done?
Joules (J)
What is the equation for work done?
Work Done (J) = Force (N) x Distance (m)
What is a Watt?
a J/s
What is the unit for power?
A Watt
What is the equation for power?
Power (W) = Energy Transferred (J)/Time (s)
The power rating will be greater is work is done over a ………………… period of time
shorter
What is the origin of the word ‘Kinetic’?
The greek word ‘kinesis’
What happens to wasted energy?
wasted energy is dissipated to the surroundings
Why can no device be more efficient than 100%?
you can never get more energy from a machine than you put into it
What is one of the most efficient appliances?
A heater/radiator
How many watts is 1kW?
1000
The more powerful an appliance is the …………… the rate which it transfers energy
faster
Wasted energy is …………. to the surroundings
dissipated
What is a closed system?
An object or group of objects in which no energy transfers take place out of or into the energy stores of the system
What is energy?
Energy is the ability to do work
What is the unit of measurement for energy?
Joules (J)
What is a sankey diagram?
A diagram representing the amount of useful and wasted energy
What does the top path on a sankey diagram represent?
Useful energy
What does the bottom path on a sankey diagram represent?
Wasted energy
