power + energy gcse physics

Energy

The ability to do work

A system

An object or a group of objects working together

Ten forms of energy

Magnetic, Internal (thermal), Chemical, Kinetic, Elastic potential, Electrostatic, (sound), Gravitational Potential and Nuclear

Magnetic

It is the energy stored when repelling poles have been pushed closer together or when attracting poles have been puller further apart

How do magnets work?

When two of the same poles are close together, they repel

When two different poles are close together, they attract

Internal/thermal energy

It is the total kinetic energy + potential energy of the particles of an object (mostly vibrations

What are the particles like in hotter objects?

the particles have more internal energy and vibrate faster.

Temperature

the measure of how hot an object is

Heat

Total kinetic energy of particles in an object

Conduction

The flow of thermal energy from a hotter object to a colder object without overall movement of the material itself

Thermal energy in solids

Atoms of a solid are held by chemical bonds but the atoms are free to vibrate.

When a part of the solid gains thermal energy, the atoms vibrate faster with more amplitude.

The vibrations pass through atom to atom

transferring thermal energy

Thermal energy in liquids

Since water is a bad conductor of heat, we use convection to heat it: that's why kettles and saucepans use heat at the bottom so the convection currents set up easily

Thermal energy in gases and non

metals

Metals

Good conductors

Chemical energy

Energy stored between chemical bonds

How does chemical energy work

Energy is absorbed to break bonds (an endothermic reaction)

Energy is released when new bonds are formed (an exothermic reaction)

transfers energy into the surroundings

Kinetic energy

The energy of a moving object

Why does a moving object have kinetic energy?

A moving object has kinetic energy because it has work done on it

What is kinetic energy equal to

work done

What happens when work is done

energy in one form is transferred to the kinetic energy of the moving object

How do you stop a moving object?

you have to put the same amount of energy to stop it (bring it back to rest)

Elastic potential energy

The energy stored when an object is stretched or squashed

When stretched, the elastic band gains elastic potential energy

Electrostatic/electrical energy

The energy stored when repelling charges have been moved closer together or when attracting charges have been pulled further apart

Can electrical energy be stored

can't be stored but it can be converted into other forms of energy and then stored

Gravitational potential energy (GPE)

The energy of an object at a height,when an object is lifted in a gravitational field, energy is transferred to a gravity store.

Calculation for GPE (j)

mass (kg) x height (m) x gravitational field strength (n/KM)

Nuclear energy

A form of energy that is released from the nucleus (the core atoms, made from protons and neutrons)

Two ways to produce nuclear energy

Fission and fusion

Fission

Nuclei of atoms split up into several parts, harnessed around the world today to produce electricity

Fusion

Nuclei of atoms fuse together

Energy pathways

Energy being carried from one place to another

Types of energy pathways

Mechanical work, Electrical work, Heating and Radiation

Mechanical work

when a force moves through a distance

ex

lifting an object, pedalling a bicycle

Electrical work

when a charge moves through a potential difference

ex

electrical devices

Heating

through a temperature difference

ex

heat being generated by rubbing stones together

Radiation

example

Where does energy transfer from

tends to be transferred from a concentrated store to a dispersed store, making it less useful for doing anything further

this energy ends up warming the environment

Efficiency

A system is more efficient if it can produce more output energy with less input

Calculation for efficiency

(useful energy output)/(total energy output) x 100

Example of efficiency

Some light bulbs are given a higher energy rating than others because less of the input energy is lost as thermal energy

Ways to increase efficiency

Thermal insulation, lubrication and streamlining

Thermal insulation

slows the conductive heat flow and convective heat flow)

Lubrication

reduces friction, typically in machinery

Streamlining

changing the shape of an object so it doesn't experience too much air resistance

Thermal conductivity

The ability to transfer or conduct heat

The higher the thermal conductivity…

The higher the thermal conductivity, the higher the rate of energy transfer by conduction across the material

The thicker the walls of a building…

the slower its rate of cooling

How do thicker walls have a slow rate of cooling

Thicker walls transfer heat by conduction more slowly than thinner walls. By adding a material of low thermal conductivity to the walls, reduces the heat loss because the lower the thermal conductivity, the slower heat passes through

Law of conservation energy

Energy cannot be created or destroyed

Formula for energy (j)

Power (w) x time(s)

What do sankey diagrams do and what do they look like

Represents energy transfers

The width represents the amount of energy

Width of the two arrows should add up to the width of the starting box

What is power

The rate of the transfer of energy

Formula for power

work/time or energy transferred/time

what does 1 watt equal

1 j/s (joule per sec)

formula for work done (j)

force(n) x distance moved in the direction of the force

Renewable energy sources

can be replenished (during the human life time) as it is used

Non

renewable energy sources

Coal

non

Adds to greenhouse gas pollution adds carcinogenic (potentially causing cancer) substances air, water and land

affecting health of the surrounding communities

Oil

non renewable resource Pollution

Gas

Non

Carbon emissions trap heat in the atmosphere

leading to climate change

Burning natural gases releases methane

Nuclear

Non

Biofuel

Renewable

Created from agricultural waste

low visual impact is very reliable

Reduces greenhouse gases

Can cause air water pollution and increases requirements

Wind

renewable Usually the turbines have to be in a windy/area and the natural environment has to be altered. Noise and visual pollution

Does not release carbon emissions

Hydroelectricity

Renewable Building it has environmental impacts

Geothermal

renewable They discharge sulphur, nickel, silica compounds, vanadium and arsenic

Tidal

Renewable Not reliable because the power generated is not at the required level. Tidal movements are constant.Changes in water and salt levels can harm local ecosystems

Solar

Renewable Not a huge environmental impact but very expensive to install and maintain

Waves

Renewable

Presence of wave

energy devices can disrupt marine habitat and disturb them