P1- Conservation and dissipation of energy Flashcards
8 energy stores
Kinetic
Heat/thermal
Magnetic
Gravitational potential
Chemical
Elastic potential
Electrostatic
Nuclear
4 ways of energy transfer
Mechanical
Electrical
Heating
Radiation
How do Sankey diagrams work?
One arrow then splits into two or more points, showing transfer of energy to dif stores
Closed system definition
No energy is dissipated into the surroundings
Conservation of energy definition
Energy can be stored and transferred but never created or destroyed
Pendulums
Movement and energy stores?
Constant speed?
In vacuum?
-Moves towards middle, gravity changes store from GPE to KE
-Moves away from middle, KE to GPE
-Air resistance slows it down, thermal energy to surroundings
-If in vacuum, no air resistance,swing forever
Bungee jumping
High GPE to KE to EPE
Comes to stop with all energy as EPE
EPE to KE to GPE
Lower height as energy transferred to surroundings
Work definition
Energy transfer when a force moves an object through a distance
What does energy transferred equal?
Work done
Amount of work done depends on 2 things?
Size of force acting
Distance the objects moves
Work done to overcome friction is transferred to…?
Thermal energy store
What happens when you rub your hands together?
Muscles do work to overcome the friction. Work is transferred as thermal energy to hands.
Energy needed for an object to be raised depends on 2 things?
How far it is raised
The weight
Kinetic energy definition
Energy an object has due to it’s motion
Elastic energy definition
Energy stored in an elastic object when stretched
Spring constant
A measure of the stiffness of a spring
Useful energy
Energy transferred to where it’s wanted in the way it’s wanted
Wasted energy
Energy that isn’t usefully transferred
Friction
What happens when two surfaces rub together?
How to reduce friction?
Effect on surroundings?
Friction causes them to heat up
Lubricant, less heat wasted
Wasted energy transferred to surroundings, become warmer
Dissipation effect on energy
As energy spreads out it becomes less useful
Efficiency
Definition
How can it be written?
Key point?
Proportion of energy transferred usefully
Percentage or decimal number
Can’t be greater than 100%
Input energy
Energy supplied to a device
4 key ways to improve efficiency
Lubricate moving parts to reduce friction
Use low resistance wires
Cut out noise
Streamline objects
Useful and wasted energy for a light bulb, kettle and hairdryer
Light bulb U-light emitted W-heat emitted
Kettle U-energy heating water W-energy heating kettle
Hairdryer U-energy to blow air W-sound of motor
Power
Rate of energy transfer or energy per second
How does the power an appliance has affect its energy?
More powerful appliance, faster rate it transfers energy
