Conservation and Dissipation of Energy Flashcards
What is the unit of energy?
Joules (J)
What are the different types of energy stores?
Chemical, kinetic, gravitational potential, elastic potential and thermal
What is the Law of Conservation of Energy?
Energy cannot be created or destroyed
What is work?
Work is done on an object when a force causes the object to move
How does the energy transferred effect the work?
Energy transferred = Work done
What is the relationship between work and friction? Give some examples.
Work need to be done to overcome friction between objects. Examples are:
• Rubbing hands together
• Brake pads/discs
• Meteorites
How does a gravitational potential energy store work?
Increases as an object is moved higher, decreases as an object is moved lower.
What is a kinetic energy store?
The energy an object has because it is moving.
Faster = more KE
Heavier = more KE
What is the equation for work done?
Work Done = Force x Distance (W=Fxs)
What is the equation for gravitational potential energy?
GPE = Mass x Gravitational Field Strength x Height
Ep =mxgxΔh
What is the equation for kinetic energy?
KE = 0.5 x mass x speed2 (Ek =0.5xmxv2)
What is useful energy?
Where energy is transferred to where it is wanted in the way it is wanted
What is wasted energy?
Energy that is not usefully transferred
What is dissipation?
Wasted energy that is transferred to the internal energy of the surroundings and gets spread out.
What is efficiency?
How much of the energy transferred to a system is transferred usefully. Can be a decimal (e.g. 0.25) or a percentage (e.g. 25%).
What is an electrical appliance?
A device that transfers electrical energy into useful energy e.g. TV, toaster, motor, heater, kettle.
What is power (P)?
•How much energy is transferred per second.
•Measured in Watts, W.
•More powerful device = more energy transferred per second.
How can power be used to work out efficiency?
•Power can be used to work out efficiency because power is a rate of energy transfer.
•Useful Power output = useful energy transferred per second.
•Total power input = energy transferred per second.
•Can also be a decimal or a percentage.
What is the equation for wasted power?
Power wasted = total power in – useful power out.
What is the equation for efficiency?
Useful output energy ÷ Total input energy
What is the equation for power?
Power = Energy ÷ Time (P=E÷t)
What is another equation for efficiency?
Efficiency = Useful power out ÷ Total power in
