P1 Flashcards
What are the 8 different energy stores
Thermal, kinetic, gravitational potential, elastic potential, chemical, magentic, electrostatic, nuclear
What are the 4 ways energy is transfered
Mechanically, electrically, heating or radiation
What is a system
A single object or a group of objects
What happens when a system is changed
Energy is transfered. Into or away from the system
What are closed systems
Systems where neither matter nor energy can enter of leave the system
Whats another way of saying energy transfered
Work done
Example of how energy can be transfered through heat
Boiling water in a kettle . Water is system and energy id transfered to the water by heating into the waters thermal energy store.
Example of a frictional cause of transfer of energy
Friction between car’s brake and its wheels does the work as it slows down. It causes an energy transfer from wheel’s kinetic energy store to the thermal energy store of the surroundings
What is the conservation of energy principle
Energy can be transfered usefully, stored or dissipated, but can never be created or destroyed
What is dissipated energy
Wasted energy because the energy is being store in an unuseful way
Example of dissipated energy
A mobile phone is a system, when you use your phone, energy is usefully transfered from the chemical energy store of the battery in the phone. But some of the energy is dissipated and this dissipated energy is transfered to the thermal energy store of the phone
What is power in physics
Rate of energy transfered or rate of doing work
What is power measured in
Watts
Equations to calculate power
Power = energy transfered/time
Power = work done/time
What does lifting an object in a gravitational field require and what does this cause
Work and this causes a transfer in energy to the gravitational potential energy store of the raised object. The higher the object is lifted, the most energy is transfered to this store
Gpe
Gravitational potential energy store
What does the amount of energy in a gpe store depend on
Mass height and strength of gravitational field strength
Equation for change in energy in an objects gravitational potential energy store
E=mgh - mass x gravitational field strength x height
E= gpe (J)
M=mass kg
G= gravitational field strenfth (N/kg)
H=heght (m)
Elastic potential energy equation
E=1/2 Ke^2
E= elastic potential energy (J)
K= spring constant (N/m)
E= entension (m)^2
How do you know if something has a kinetic energy store
Anything that is moving has energy in it’s kinetic energy store
When does energy travel to and from the kinetic energy store
When an object speeds up, energy is transfered to this store. When an object slows down, energy is transfered away from this store
What does energy in the kinetic energy store depend on
The objects mass and speed. The greater mass, the faster the object travels, the more energy there will be in its kinetic energy store
Equation for kinetic energy
E= 1/2mv^2
E= kinetic energy (J)
M= mass (kg)
V = speed (m/s)^2
Why are useful devices useful
Because they can transfer energy from one store to another
How can you improve the effiency of energy transfers
Insulating objects, lubricating them or making them more streamlined
Energy effiency equation
Useful power output/total power output
Equation for useful energy transfer
Useful output energy transfer / total input energy transfer
What is one thing that is 100% energy efficient and why
Electric heaters because in the electrostatic energy store is transfered to ‘useful’ thermal energy stores
Ultimetely, all energy ends up transfered to
Thermal energy stores
Energy is transfered between stores electrically by…
Electrical appliances
Why does moving charge transfers energy
Because it does work against the resistance of the circuit
What are electical appliances designed to do
Transfer energy to componants in the circuit when a current flows
What does it mean if the current is higher
The more energy is transfered to the thermal energy stores of the componants
What is the power of an applience
The energy that it transfers per second. So the more energy it transfers in a given time, the higher it’s power
Equation for energy transfered
Energy transfered (J) = power (W) x Time (S)
What are appliances often given
Power rating -
What does a power rating tell you
The maximum amount of energy transfered between stores per second when the appliance is in hse
What does a lower power rating mean
Less power rating means less electricity an appliance uses in a given time and so the cheaper it is to run
