Class Notes 1/27/09

Intro:

-batteries produce electrons

-electrochemical rxns=chem rxns that produce electrons

-two terminals, one positive the other negative

-electrons collect on negative side

-internal resistance=speed of electron production by chemical reaction

-internal resistance controls how many electrons can flow between terminals

-electron must flow from neg to pos for chem rxn to take place (occurs through a wire)

-batteries retain energy as long a wire is not connected

Battery History

-created by Alessandro Volta in 1800 by stacking alternating layers of zinc, blotting paper soaked in salt water, and silver-known as a voltaic pile

-top and bottom layers must be different metals

-voltage and current can be measured if you attach a wire to the top and bottom of the pile

-each layer increases the voltage by a fixed amount

-before the invention of the electrical generator, the Daniel cell (a wet cell consisting of copper and zinc plates and coper and zinc sulfates) was common of operating telegraphs and doorbells. 

-the Daniel cell is also known as crowfoot cell, gravity cell, wet cell

-it is made by placing a copper plate at the bottom of a glass jar and then pouring copper sulfate solution over the plate to half-fill the jar. 

Rechargeable Batteries

-lead acid cell is used in almost all rechargeable batteries

-reverses natural flow from negative to positive, reverses process

-usually requires adapter within built in batteries, nickel cadmium and nickel metal hydride-most commonly used today

-different rates of recharging-slow 14-16 hrs, quick 3-6 hrs , and fast less than 1 hr

-in cars the alternator, device used to convert to electrical energy and applies it to the battery

-memory effect-charge battery full because batteries have memory, battery could forget that it has the full capacity

-culprit of this=cadmium crystals

-can be avoided if you cycle through a full charge

-no battery is permanent

-rechargeable batteries postpone inevitable

Battery Rxns and Chemistry

-two different plates in acid that acts in solution called electrolyte

-lead combines with sulfuric acid, two different plates combine in electrolyte which end up producing extra electrons

-water builds up from the production of hydrogen

-if you apply current to the battery at the right voltage, the plates can reform again so the battery can be reused.

-used in cars

Battery Arrangement and Power

-arranged in serial or parallel arrangement

-serial voltage is added, parallel current is added

-batteries can produce a maximum current

- measured through 500 milliamps/hr 

Second Semester!

Hi Larry!

I think the presentations are a good idea to start off the class and break the ice. It also helps  combine the interdisciplinary aspects of the honors program. However, I do wish we could go up with our whole group...

I personally liked the use of the video clip in the beginning of Raj's groups presentation because it was able to catch everyones attention. 

It was cool to brainstorm with my own group about an article that I had such an interest in. I'm really into education and education reform. I myself struggle and have always struggled with understand the concepts of science. I can't just read through a textbook and understand photosynthesis or see the molecular structure of hydrogen. I need to be able to really see examples of these things. I need to be able to talk about out loud with other people to understand any of it. I always need to have some concepts explained to me over and over and over again in order to get it through my thick skull. 

The rubric for the class presentations seems fine to me. The only suggestion I had is that the "4" section seems very similar to the "5" section. I think that 4 section also demonstrates a nearly flawless presentation so maybe the standards to receive a "5" are a bit too high. 

**Notes from Class**

-~Energy Systems Cycle~-

find mine harvest->process refine convert->transport->operate maintain->decommission

Potential Side Effects of this cycle: 

~Find mine harvest-raise land, destroy natural habitat, use more energy than it would produce, increase they price to harvest it, decrease the supply, soil erosion, chemical run off

~Process Refine Convert-pollution from smoke stacks, global warming, health and safety, re-education of the work force, takes energy to refine

~Transportation-pollution, destruction of natural habitats, smog

~Operate Maintain-could take more energy to produce than it does to release, dangerous living conditions, dangerous jobs

~Decommission-pollute water, destroy land, radiation, infertile land, could have significant effect on animals, eye sores, decrease property values, in rivers flow is slowly so water doesn't naturally cleanse itself

lifetime of a blade-about ten years? but no way to recycle them...

Where do we put hazardous waste??