Energy Transfers Flashcards
What are the energy stores?
- Chemical
- Kinetic
- Gravitational
- Elastic
- Thermal
- Magnetic
- Electrostatic
- Nuclear
What are the energy transfers?
- Mechanical
- Electrical
- By heating
- By radiation (light and sound)
What is the Principle of the Conservation of Energy?
Energy cannot be created or destroyed, it can only be transferred from one store to another
What is the Equation for Efficiency?
Efficiency = (Useful energy / Total energy) x 100
What is conduction
The transfer of heat from hot to cold through a solid material, by collisions of vibrating particles and free electrons in metals
What is convection
The transfer of thermal energy, by moving particles in a gas or liquid due to differences of density
What is the important information about infra-red?
All objects emit and absorb infra-red
Hotter the object the more it’ll emit per sec
Object will stay at a constant temp if it emits at the same rate as it absorbs
Absorbs more than emits -> gets hotter
Emits more than absorbs -> gets colder
Examples of convection in everyday life
Immersion heater - Water is heated from a coil
Water heats up and rises because it’s less dense
Fast-moving particles collide with slow-moving particles and they transfer energy
Water cools and becomes denser causing it to sink
How can reduce energy transfers in a system by conduction?
Using materials with a lower thermal conductivity
Insulation
Using an insulating material (materials that are poor conductors of heat) such as wool or cotton to trap air, reducing the rate at which heat is lost.
Unit of mass
Kilogram (Kg)
Unit of energy
Joule (J)
Unit of length
Metre (m)
Unit of velocity/speed
Metre/ second (m/s)
Unit of acceleration
Metre/ second^2(m/s^2)
