Lesson 1 Notes

Lesson 1 Notes - Lesson 1 Articulating appliance selection...

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Lesson 1 Articulating appliance selection and their respective impacts on energy use Discussing various forms of energy, and describe how energy transformations occur Calculating the efficiencies of devices Devising conservation strategies Calculating energy costs and discuss various forms of energy (microwaves, etc) Devise electricity consumption reduction approaches. Conduction The electricity supplies a stream of electrons which whiz around in the coil at very high speed (close to the speed of light) until they encounter some resistance. Impeding the flow of electrons produces heat, and so the metal coil (on which the kettle sits) becomes hot. The first heat transfer mode to the kettle will be conduction. The metal of the kettle is in contact with the metal of the heating element and heat always “flows” from hot to cold so there is heat transfer. The atoms in the heating element behave a little like slam dancers (dancing in a single area of the floor) at a Green Day concert. They will pass on their energy to the surrounding people making them more active and in turn passing on their energy to another layer, and so on, until the whole concert is full of crazed slam dancers. The atoms will be fixed in their relative positions but as they heat up they will vibrate more and pass along some of that energy. Metals tend to be very good at passing heat and this is why the kettle is metal (so I can quickly heat it up). Radiation Radiative heat transfer is how the “warmth” of the sun is transferred to you when you're out or how you warm your hands in front of the fire. It is electromagnetic radiation and it does not need a medium to propagate. Thus, it can travel through space Convective The water molecules are free to roam about as they are not fixed in relative positions (unless frozen) like the metal atoms. So as a water molecule heats up it has more energy and travels further. The molecules moving around have lots of collisions (think bumper cars) but this molecular billiards occurs without energy loss and so imagine breaking at pool but the balls never stop, they will keep on colliding until there is a distribution of energy. This distribution will be a certain shape with a certain portion of the molecules having certain energy levels. As the water warms up this distribution will simply shift to the right into a higher energy level (temperature). Refridgerator At the back there is a heat exchanger, a coil where the heat from inside the refrigerator can be dissipated—yes this means that in the summer your refrigerator is pumping out heat which you are removing with the air conditioner (silly isn't it!) But as heat flows from hot to cold how did we manage to get it to flow the other way? We used a heat
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pump , which we give energy to so we can move heat; this is achieved because of the
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Lesson 1 Notes - Lesson 1 Articulating appliance selection...

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