Physics: Energy and Power

TOPIC: ENERGY & POWER

TOPIC: ENERGY & POWER

What are the 10 forms of energy (Most Kids Hate Learning GCSE Energy Stores)

Magnetic

Kinetic

Heat

Light

Gravitational Potential

Chemical

Sound

Elastic

Electrical

Nuclear

What are the 8 energy stores

Kinetic

Gravitational Potential

Chemical

Elastic Potential

Nuclear

Electrostatic

Magnetic

Thermal

Definition of energy

The ability to do work

Definition of a system

An object or group of objects working together

What are the 4 energy pathways

Mechanical - (when a force moves through a distance)

Electrical - (when a charge moves through a potential difference)

Heating - (because of a temperature difference)

Radiation - (e.g light, microwaves, sound)

Where does energy tend to be transferred?

From a more concentrated store to a mire dispersed store - this make it less useful for doing anything further

Energy often ends up warming the enviornement

Definition of efficiency systems

A system if more efficient it can produce the same output energy with less input energy.

Why are some light bulbs given a higher energy rating?

Less input energy becomes heat

How can we make a light bulb more efficient?

Take less energy to do the same job in this case brightness

Why are some washing machines given a higher energy rating than others?

They are using less energy but give you the same output

How can we make a washing machines more efficient?

Reduce friction, use less water or shorter programs

Why are the breaks of a car so hot?

You use a lot of friction to slow down the car

Definition of the law of conservation of energy

Energy cannot be created or destroyed, only transformed or transferred from one form to another

What diagram can you use to represent energy transfers and calculate efficiency?

Sankey diagrams

What does FIFA stand for?

F write out the Formula you are going to use

I Insert the values that you have been given

F Fine tune (rearrange and calculate)

A write Answer and UNIT

Definition if power

The time rate at which work is done or energy is transferred - (if someone does the same amount of work as another, but does it more quickly, they are said to be more powerful)

What is work done, time & power measured in?

Work done - joules (J)

Time - seconds (s)

Power - watts (W)

Fossil fuels (coal, oil, gas)

• All non renewable

• Coal - electricity & heating - CO² - global warming

• Oil - transport, electricity, heating - mining damage

• Gas - transport, electricity, heating - oil spills

Nuclear

• Renewable

• Used for: electricity

• Environmental impact: nuclear waste, mining damage

Bio-fuel

• Renewable

• Used for: transport, electricity, heating

• Environmental impact: land used is unavailable for agriculture

Wind

• Renewable

• Used for: transport, electricity

• Environmental impact: visual impacts, noise pollution

Hydro-elctricity

• Renewable

• Used for: electricity

• Environmental impact: visual impact, land flooded

Geothermal

• Renewable

• Used for: electricity, heating (locally)

• Environmental impact: visual impact

Tidal

• Renewable

• Used for: electricity

• Environmental impact: tidal barrage can affect wildlife adapted to tidal patterns

Sun

• Renewable

• Used for: electricity, heating (direct)

• Environmental impact: visual impact

Waves

• Renewable

• Used for: electricity

• Environmental impact: marine habitats, noise pollution

What are the 4 common HUGE prefixes

Kilo, k - (10³)

Mega, M - (10^6)

Giga, G - (10^9)

Terra, T - (10^12)

TOPIC: THERMAL ENERGY

TOPIC: THERMAL ENERGY

Which regions are thermal energy transmitted from and to?

From hotter regions to colder regions.

When two regions or objects are the same temperature there is no overall transfer of thermal energy - they are in thermal equilibrium

What are the three ways thermal energy may be transmitted?

Conduction

Convection

Radiation

Definition of conduction

The movement of heat through a substance by the collision of particles.

Definition of convection

When warmer fluids (liquids & gases) rise up through cooler fluids because that are less dense than the cooler surroundings

Definition of radiation

Warm objects emit radiation infrared rays in all directions. These rays travel at the speed of light.

What are good conductors of heat but poor insulators?

Metals (e.g copper, aluminium)

What are good insulators but poor conductors of heat?

Non-metals (wood, plastic, glass, air)

Why is air a bad conductor of heat?

Since conduction involves collision of particles, it takes longer to pass on energy in air (a gas) as the particles are further apart

Definition of thermal conductivity

A measure of how well a material conducts thermal energy when it is heated

Definition of U-values

They measure the rate of heat transfer through a given area of a material or structure

What is the difference between thermal conductivity and U-values?

Thermal conductivity just measures how easily heat travels through a material. It doesn’t take into account of thickness or complex structure.

Thermal conductivity

For Heat Transfer: A higher number is better. A higher thermal conductivity means the material moves heat faster and more efficiently.

For Insulation: A lower number is better. A lower thermal conductivity means less heat energy escapes, resulting in better insulation

How do you know if the material is a better insulator and what are the methods?

If the U-value is lower. Cavity wall insulation, double glazing and loft insulation are all methods of lowering U-values

Definition of Infrared Radiation

An electromagnetic wave we cannot see but feel as heat. Any hot object will emit infrared radiation including humans

Definition of a ‘black body’

An object which is a perfect absorber of electromagnetic radiation (including invisible light). Any radiation that hits it is neither reflected nor transmitted(passed through) but absorbed

How can you recognise a ‘black body’?

By the radiation they emit - examples our the sun & a filament lamp

If the Leslie cube in the previous question had surfaces covered in different materials

Which material would emit be the best and emit the highest intensity of infrared radiation?

Black matt - best absorber & emitter due to biggest change in temperature

Shiny Silver - worst absorber & emitter due to smallest temperature change

Definition of payback time

The time taken to recover the cost of an investment due to the savings it gives

Formula for calculating payback

payback = the initial investment / annual cash inflow