Topic 1 Energy Stores And Systems Flashcards
Why is energy never used up?
It is just transferred between different energy stores
E.g law of conservation of energy
Name all 8 energy stores
Thermal energy store (internal energy store)
Kinetic energy store
Gravitational potential energy store
Elastic potential energy store
Chemical energy store
Magnetic energy store
Electrostatic energy store
Nuclear energy store
How can energy be transferred?
Mechanically (by a force doing work)
Electrically (work done by moving charges)
Heating
Radiation (light or sound)
What is a system?
Single/group of objects you are interested in
What happens when a system changes
Energy is transferred it can be transferred into or away from the system between different objects in the system or between different types of energy stores
What are closed systems
Neither matter no energy can enter or leave the net change in the total energy of a close system is always zero
Example of energy being transferred by heating
Boiling water in a kettle
Water is the system
Energy is transferred to the water (from the kettles heating element) by heating into the waters thermal energy store causing the temperature to rise
Another way to think of energy being transferred by heating
Could think of kettles heating element and water as a two part system
Energy is transfer electrically to the thermal energy store of the kettles heating element and transfers energy by heat to the waters thermal energy store
What is work done another way of saying
Energy transferred
When can work be done
When a current flows (work is done against resistance in a circuit)
By a force moving an object
Example of doing work throwing a ball
Initial force exerted by a person to throw ball up does work,
Causes energy transfer from chemical energy store of persons arm to kinetic energy store of the ball and arm
Example of dropping a ball
Ball dropped from hieight is accelerated by gravity
Gravitational force does work
Energy transferred from balls gravitational potential energy store to its kinetic energy store
Example of friction
Friction between cars brakes and wheels does work as it slows down
Causes an energy transfer from the wheels kinetic energy store to the thermal energy store of the surroundings
Example of transfers in the collision of a car and a stationary object
Normal contact force between the car and the object does work.
Causes energy to be transferred from the cars kinetic energy store to other energy stores e.g electric potential and thermal energy stores
Some energy might also be transferred away by sound waves
