Physics energy stores and transfers

what is a system

a system is an object or group of objects. A system could be large or small, incorporating just one object, or a whole group of objects and their surroundings

Table of Energy stores

• Kinetic

• Gravitational

• Elastic

• Magnetic

• Electrostatic

• Chemical

• Nuclear

• Thermal

Kinetic

Moving objects have energy in their kinetic store

Gravitational

Objects gain energy in their GPE when lifted

Elastic

Objects have energy in their elastic potential store if they are stretched, squashed or bent

Magnetic

Magnetic materials interacting with each other have energy in their magnetic store

Electrostatic

Objects with charge interacting with one another have energy in their electrostatic store

Chemical

chemical reactions transfer energy into or away from a substance’s chemical store

Nuclear

Atomic nuclei release energy from their nuclear store during nuclear reactions

Thermal

All objects have energy in their thermal store. the hotter the object is, the more energy it has in its store.

Energy transfers

• Mechanical

• Electrical

• Heating

• Radiation

Mechanical

When force acts on an object like pulling, pushing, stretching, squashing.

Electrical

A charge moving

Radiation

energy transferred by electromagnetic waves

Describe the energy transfer:
A battery powering a torch

It is transferred Electrically from the Chemical store to the Thermal store of the bulb

Describe the energy transfer:
A falling object

Energy is transferred from the gravitational store to the kinetic store through a mechanical transfer

conservation of energy states:

Energy cannot be created or destroyed, it can only be transferred from one store to another. It can however be spread out / dissipated

e.g:

A bat hitting a ball

The moving bat has energy in its kinetic store, some of that energy is transferred to the thermal store of the ball mechanically. This energy transfer is wasted, it is not useful.
Since the rest of the kinetic energy gets dissipated and not fully into the ball.

e.g:

Trampoline

When jumping, The person has energy in their kinetic store. when the person lands on the trampoline, most of that energy is transferred to the elastic potential store of the trampoline. The energy is transferred usefully back to the kinetic store of the person.

Efficiency

If a system has high efficiency, then most of the energy transferred is useful.
If a system has low efficiency, then most of the energy transferred is wasted

Efficiency formula

Efficiency is represented as a percentage.

Useful energy output Over Total energy output x 100%

Conduction

A material is a good conductor if it transfers energy by heating. Metals are extremely good thermal conductors because they have delocalized atoms that help pass the energy through atoms.

Insulators

Insulators are bad at transferring energy. Non-metals are Insulators, as well as liquid and gases. this is why rugs are used to warm your feet, since it cannot transfer the heat anywhere because it is an insulator

Convection

Convection is the main way that thermal energy is transferred through liquids and gases. it cannot occur in solids.

Thermal radiation

All bodies(objects), no matter what temperature, emit infrared radiation.

The hotter object, the more infrared radiation it radiates. infrared radiation can be detected using special camera.

Shiny objects are the worst at emitting and absorbing thermal radiation, whilst Black objects are the best.