Energy Resources and Energy Transfers

Eg. A 60W tungsten filament bulb uses 60J of energy every second. It is 5% efficient. How much of the total energy output per second is useful light energy?

-Efficiency= useful energy output/total energy output x 100% 5%= useful energy output/ 60J x 100% 5/100 = useful energy output/ 60J So useful (light) energy from bulb = 5 x 60J/ 100 = 3J each second

Consequences of Global Warming

1) Higher temperatures cause seawater to expand & ice to melt, thus increasing the sea level - if it rises too much, it can cause flooding & destroy habitats 2) Increasing temperatures & the amount of rainfall changes may change the distribution of wild animals & plant species - species needing warmer temperatures may become more widely distributed whilst species needing cooler temperature may have smaller ranges 3) Changes in migration patterns 4) Biodiversity could be reduced if some species are unable to survive a change in the climate, thus becoming extinct

Thermopile and Leslie's Cube

A Thermopile is a device used to detect infrared radiation, by converting the radiation, by falling into the cone of the device which is then turned into electrical energy. The more radiation the greater the production of electricity. Then it is measured using a sensitive 'spot galvanometer". Leslie's Cube Is a metal cube with 6 flat sides, 4 vertical faces are finished differently. The faces consist of Matt black, shiny white, polished metal and malt white. To use this, fill the cube with hot water so that we can see the face that emits Most radiation under the same circumstances.

Sankey Diagram

A diagram that represents energy transfers by arrows. The width of each arrow depends on the amount of energy it represents.

How weather is driven by convection currents?

Convection drives the circulation of air in the earth's atmosphere. Sun heats air near equator - becomes less dense and rise upwards. Air cools as it rises and becomes more dense than the air around it which then spreads out and descends towards the equator again.

Devices that illustrate infrared radiation

Different surfaces emit infrared radiation which can be illustrated extremely well using devices called Leslie's cube and Thermopile.

Equation for the efficiency of energy conversion system

Efficiency= useful energy output/total energy output x 100% Efficiency - no unit of measurement Total energy output - Joules (J)

Energy Transfers

Energy transfer is considered as the proportion of energy input that is wasted. When saying 'wasted' it means that energy is transferred Into stores other than the useful store required. Real Systems have unwanted Energy output, so it can never have 100% efficiency.

Global Warming

Global Warming occurs because the Sun emits infrared radiation that passes through the the vacuum of space freely, penetrates the Earths atmosphere all the way to the surface and heats the earth surface. Infrared Radiation is able to pass through space and penetrate the earth's atmosphere because the Sun originally emits extreme heat which has short waves. However, it does not heat the Earth to such extreme heat like the Sun.

Thermal Radiation - Hot and Cold bodies

Hot Bodies: -release energy, short waves, penetrating thermal radiation. Cold bodies: -release weak, longer waves, less energetic thermal radiation that is less penetrating. Important Info: -Air absorbs longer waves of infrared raditaion.

Metals conductivity

Metals are good conductors of electricity and heat well because particles are made up of easily lose electrons. The electrons randomly wander around the metal. However, since there are so many electrons wandering that they have no overall effect of movement. Particles do collide with each other and transfer kinetic energy(motion energy) with the other particles they collide with.

Greenhouse effect

Over the year's man kind burnt huge amounts of fossil fuels which are carbon base, creating carbon dioxide as waste. The carbon dioxide is called a greenhouse gas and it absorbs long waves of infrared radiation strongly. The Greenhouse effect is the trapping of the sun's warmth in a planet's lower atmosphere due to the greater transparency of the atmosphere to visible radiation from the sun than to infrared radiation emitted from the planet's surface.

Convection

Process by which, in a fluid being heated, the warmer part of the mass will rise and the cooler portions will sink. Fluids near the heat source gains energy, becomes less dense and rises, forms a conversation current and heat fluid completely.

Summary of 4 faces of Leslie's Cube

Shiny surfaces are good reflectors of Radiation but poor emitters of infrared radiation. Matt surfaces are poor reflectors but good absorbers of radiation because the radiation is absorbed which leads the surface to heat up. Matt surfaces also are good emitters of infrared radiation ( good at emitting infrared radiation).

Earth emits Infrared Raditaion

Since the surface of the earth is relatively cool it emits long waves of infrared radiation. However, It is unable to penetrate the earth's surface very far. The radiation is absorbed by the Earth's atmosphere and heats it up. Some would escape, otherwise the Earth would have been a Sauna. Without the effect, Earth would have been you cold to support life.

Stored/Conserved and transferred energy

Stored/Conserved- Thermal, chemical,Motion, Nuclear, Sound, Elastic, Gravitational, magnetic and kinetic energy Transferred energy- Light, Radient and Electrical energy

Conduction

The direct transfer of heat from one substance to another substance that it is touching. Meaning that heat travels from one place to another. The heat discussed, is mainly kinetic energy (molten energy). It is the particles (atoms and molecules) that vibrate to make up hot matter. The separation between particles in hot solids are greater than Colin solids - due to vibrating particles. Explains the expansion of objects when heating.

Thermal Radiation

Thermal Radiation or Infrared Radiation, is the thermal energy/ heat you feel from the Sun. Thermal Energy travels from the Sun to the Earth traveling in a straight line, passing space. It is a electromagnetic wave like light, because it casts a shadow Just like light but has a longer wavelength.

What are the 10 forms of energy?

Thermal, Light, Chemical, Motion, Nuclear, Sound, Electrical, Elastic, Radient, Gravitational (potential), Magnetic and Kinetic Energy

Example of Convection

When heating a kettle of water, water molecules near the heat source gains energy and heats up. Once the molecules are heated, they would start to faster and become less dense. Molecules then rise because its less dense. Cooler molecules replace heated molecules. This is a continuous circle.

Thermal Radiation - Absorb And Release

When objects are in contact with Thermal Radiation, it absorbs and heats the object. The colour black absorbs more heat than any other colour. All bodies also release Thermal Radiation. From things that are very cold (Space) to the hottest things (Sun). However, the hotter the body: -the more energy radiation it contains. -shorter wavelength of the radiation. -more penetrating the radiation.