P1 - Energy Stores✔️ Flashcards
Explain what a chemical energy store is? List some examples?
is the energy transferred during chemical reactions - stores include fuels, food or chemicals found in batteries
Explain what a kinetic energy store is?
Describes the energy an object has due to its movment
Explain what a gravitational potential energy store is?
used to describe the energy stored in an object because of its position such as an object above the ground
Explain what an elastic energy store is?
Describes the energy stored in a springy object when you stretch or squash it
Explain what a thermal energy store is?
Decribes the energy a substance has because of its temperature
Explain what happens when an electric kettle is used to boil water - refer to energy stores?
The current in the kettle’s heating element transfers energy to the thermal energy store of the water and kettle - which heats up the water
Explain what happens when a object is thrown into the air - refer to energy stores?
When an object is thrown into the air the object slows down as it goes up because energy is transferred from the objects kinetic energy store to its gravitational potential energy store and when the object starts to fall freely the force of gravity causes energy to be transferred from its gravitational potential store to its kinetic energy store
What is a closed system?
A system in which no energy transfers take place out of or into the energy stores of the system - energy can be transferred between energy stores within a closed system but the total energy of the system is always the same before and after such transfers
What does the conservation of energy state?
Energy cannot be created or destroyed
Can energy be transferred between stores within a close system?
Yes energy can be transferred between energy stores within a closed system but the total energy of the system is always the same before and after such transfers
Explain why the exmaple of a pendulum in a vacuum is a closed system?
Because there is no air resistance acting on it and so no energy would be transferred from any of its energy stores and it would keep swining for ever
Give 4 examples of energy transfers?
- waves
- heating
- electric current
- mechanical
What does energy transfer equal?
Energy transferred = work done
Equation for change of gravitational potential energy store?
Change of gravitational potential energy = mass x gravitational field strength x change of height
Define useful energy?
Is energy transferred to where it is wanted in the way that is wanted
Define wasted energy?
Is the energy that is not usefully transferred
What happens when energy is dissipated?
Whenever energy is transferred for a purpose in any system, some of the energy is transferred usefully and the rest may be stored in less useful ways - this is described as wasted energy
Explain how energy is dissipated when using a phone?
When you use the phone energy is transferred from the chemical energy store to the battery in the phone - but some of the energy is dissipated in this transfer to the thermal energy store which heats the phone up
Equation for efficiency?
Efficiency = useful ouput energy transferred / total input energy supplied
How can you improve efficiency of energy transferred?
By insulating objects, lubricating them and making them more streamlined
Why are electric heaters an exception and usually 100% efficient?
Usually all the energy in the electrostatic energy store is transferred to “usefull” thermal energy stores
Why is no device 100% efficient?
Wasted energy is usually transferred to useless thermal energy stores
Why do machines waste energy?
Due to friction between their moving parts, air resistance, electric resistance and noise
Relationship between power and an appliance?
The more powerful and appliance is, the faster the rate at which it transfers energy - power is measured in watts (W)
Value of 1 watt?
1 joule
