Energy

Changes in energy stores

GEEKSLUNCH

Gravotational potential

Electric

Elastic Potential

Kinetic

Sound 

Light

U -

Nuclear

Chemical

Heat/thermal

Energy Transfers

- A system is an object or a group of objects.

- Doing 'work' is the scientific way of saying that energy had been transferred.

- Diagrams can be used to show how energy is transferred from one store to another. Two examples are the transfer diagram and the sankey diagram.

- In transfer diagrams the boxes show the energy stores and arrows show energy transfers.

- Sankey diagrams start off as one arrow that splits into two or more points. This shows how all of the energy in a system is transferred into different stores. Sometimes, the amount of energy is shown and the width of the arrow is drawn to scale.

Energy dissipation

- No system is perfect. When energy is transferred, some of that energy is dissipated (the spreading out of energy stores into less useful forms – wasted) into surroundings.

- In a mechanical system energy is dissipated through friction. Adding lubricant between surfaces reduces friction and so less heat is wasted.

Conservation of Energy

Energy can be transferred usefully, stored or dissipated but it can never be created nor destroyed.

Calculating energy changes

kinetic: Kinetic energy = 1/2 x mass x speed(squared)

elastic potential: Elastic potential = 1/2 x spring constant x entension(squared)

Work, power and efficiency

energy transferred = work done

- work done is measured in joules

- Work done = force x distance

Energy and Power

- Power is the rate at which energy is being transferred

- Power is measured in watts

- One watt = one joule per second

Efficiency

- Efficiency is how good a device is at tranferring energy input into useful energy output.

Efficiency = (useful energy input/total energy output) x 100

- It is not possible to have an efficinecy of 100% or greater. This would mean energy is being created which can't happen.

Electrical Appliances

Electrical kettle

Hair Dryer

Light Bulb

TV

Energy and Heating

Conduction

- All metals are good conductors. If one end of a metal…