JC Science - Energy

What is energy?

The ability to do work

What is the SI unit for energy?

Joules (J)

Earth's primary source of energy

sun

Two main groups of energy

1. Kinetic energy
2. Potential energy

Kinetic energy

The energy of movement

Potential energy

Stored energy

Motion (kinetic) energy

The energy of a moving object
E.g. moving car

Heat energy

Causes particles to vibrate. We feel this as a change in temperature
E.g. water heated

Electrical energy

The movement of electrons.
E.g. lamp

Sound energy

Energy caused by an object's vibrations
E.g. strumming a guitar

Light energy

-Energy in the form of moving waves of light
-Electromagnetic radiation
E.g. light emitted from a light bulb

Gravitational potential energy

The energy stored in raised objects
E.g. rollercoasters at the top of a hill

Elastic potential energy

The energy in stretched or squashed objects
E.g. a stretched bow

Chemical energy

Energy stored in the bonds of molecules
E.g. food, fossil fuels, batteries

Nuclear energy

The energy stored in the nucleus of an atom
E.g. nuclear power station

Forms of kinetic energy

-Motion energy
-Heat energy
-Electrical energy
-Sound energy
-Light energy

Forms of potential energy

-Gravitational
-Elastic
-Chemical
-Nuclear

The law of conservation of energy

Energy cannot be created or destroyed, but can convert from one form to another

Energy change/transfer

Energy changed from one form into another

Energy transfer of a lamp

Electrical -\> heat + light
Useful: light
Dissipated: heat

Energy transfer of a car

Chemical -\> kinetic, heat + sound
Useful: kinetic
Dissipated: heat, sound

Energy dissipation

When energy escapes while being changed from one form to another

Useful + wasted energy

Useful: the one we want
Wasted: the one we don't want

Efficiency

A measure of how much input energy is converted into useful output energy

Energy efficiency equation

useful energy output x100
\------------------------------
total energy input

Sankey diagrams

Sankey diagrams summarise the energy transfer occurring

Energy efficiency label

Why do machines waste energy?

-Friction between moving parts cause heat
-Sound created by machinery
-Heat lost to the surrounding air

How to improve efficiency of machines?

-Lubricate (oil) moving parts
-Cut out noise (tighten loose parts to reduce vibration)
-Add insulation around objects to prevent heat wasted

Ways to improve energy efficiency in your home

-Solar panels
-Walls, roof + floor insulation
-Turn down thermostat
-Use rugs/carpets
-Double/triple glaze windows
-Repair holes in roof
-Use curtains
-Close doors

Building Energy Rating certificate

Tells us how energy efficient a house is