Energy Flashcards
What is the rule of conservation of energy?
Total energy before a process = Total energy after a process
What is the unit of energy?
Energy is measured in joules (J)
What the main energy stores?
- kinetic store
- gravitational potential store
- chemical store
- elastic store
- thermal store
How can we tell if there is a change to the kinetic store?
If the object changes speed
How can we tell if there is a change to the gravitational potential store?
If the object ends up higher or lower than it started out
how can we tell if there is a change to the chemical store?
If a chemical reaction takes place e.g. fuel burns, so you have less fuel than when you started
How to tell if there is a change in the elastic store?
If an object changes its shape
How can we tell if there is a change in the thermal store?
If the temperature of the object changes
What are the main energy pathways?
- Mechanical working
- electrical working
- heating by particles
- heating by waves
- light
- sound
- electromagnetic radiation
What is the mechanical working pathway?
Energy transferred by a force of physical mechanism (e.g. a pulley)
What is the electrical working pathway?
Energy transferred by an electric current
What is the heating by particles pathway?
Energy transferred from a higher temperature region to a lower temperature by moving particles (conduction, convection)
What is the heating by waves pathway?
Energy transferred from a higher temperature region to a lower temperature region by the emission of infrared radiation
What is the light pathway?
Energy transferred as visible light
What is the sound pathway?
Energy transferred as a sound wave
What is the electromagnetic radiation pathway?
Energy transferred as an electromagnetic wave (radio, microwave, infrared, visible, ultraviolet, X ray, gamma)
What is the equation for work done?
Work done by a force (joules- J) = force (N) x distance moved in the direction of the force (m)
W=Fs
What is work done?
If a force acts on an object, and the object moves in the direction of the force, we say that work has been done by the force
Finish the sentence: When work is done by a force, ________
Energy is transferred between stores
What is the equation for gravitational potential energy?
Change in the gravitational potential energy store (J) = mass (in kg) x gravitational field strength (N/kg) x height (m)
GPE = mgh
What are the units for power?
Watts
What is the equation for power?
power (in watts) x time (in seconds) = energy transferred (in joules)/work done (in joules)
P x t = E
What is the definition of power?
Rate of energy transfer
Rate at which work is done
equation for efficiency
efficiency = (useful energy transferred / total energy input ) x 100
OR
efficiency = (useful power output/total power input) x 100