Not assigned ?s im just curious about them.

Discussion in 'General Electronics Chat' started by Windex, Feb 9, 2005.

  1. Windex

    Thread Starter Member

    Feb 2, 2005
    11
    0
    I was kind of curious about a few question in my book.

    It asked me What is used as a depolarizer in a flaslight cell?

    Well first i'd have to know which is being used for the cell. I mean, is it primary or secondary? And after I knew that, i'd have to figure out the company's secret formula. Of course there are some batteries listed in this book. Tell me, what do you think of this answer?

    7. Zinc, ammonium chloride, and manganese dioxide.


    Another book question which is truly important and the question wasn't very clear on it.

    Lead-acid batteries should be connected to the charger _______ the power is applied.

    For the blank I put: before.

    Is that right?

    Because there may be hydrogen gases coming out of the battery you aren't aware of and when you hook up the after the charger is on you could create a spark and BOOM!


    Another good question the book had was

    Which combination of cells should be used for a heavy load?
    a. series
    b. parallel.

    I said both. Mainly because if its heavy it will probably need lots of electrolyte from the battery and need to sustain a good current.

    Is that right?


    Also, something I've never understood being in this electronics class was how phonographs work. Seriously, this book tell me that mechanical energy added to a crystal flexes it.

    I'm thinking.. "wtf? I thought only electrical energy could distort the crystal, why is this book telling me mechanical can bend the crystal, thus having the crystal turn the mechanical energy into electrical."

    Pin going up and down creates mechanical force.
    Crystal bends from this mechanical force and in turn creates electrical energy.

    That doesn't sound right to me.

    Why would mechanical force distort the crystal? The book told me only electric could do that. Does someone think they could broaden on this?
     
  2. Nettron

    Member

    Jan 22, 2005
    29
    0
    Google for piezoelectric effect.
     
  3. vineethbs

    Well-Known Member

    Nov 14, 2004
    56
    0
    hmm i don't have an exact answer for the first question
    i think it may be some ions that are produced during the electrolytic reaction that may accumulate around the electrodes this wud reduce the reaction rate ,the depolariser wud react with this and remove it
     
  4. rukrazy?

    Member

    Mar 5, 2005
    21
    0
    What happens to the off the shelf zinc/carbon alkaline cell when it stops producing current? Is it dead? No, it is not really dead because it still has its fuel (zinc) intact. There is also plenty of plenty of potassium hydroxide left to carry out the cell reactions. So, why does the cell stop producing electrical current? Is it because the "depolarizer" gets used up? The depolarizers typically used in these cells have not changed much since the early 1900s. They are still using manganese dioxide. This is the compound that supplies the oxygen that unites with the hydrogen that results when the zinc is oxidized (burned). Without the depolarizer the carbon rod becomes coated with hydrogen gas and this puts an equal charge between the cathode (zinc) and anode (carbon). This prevents the cell from producing the reactions that generates its electrical current. Typically, manganese dioxide gets used up fairly quick in off the shelve batteries. Knowing this, all we need to do is to find a depolarizer that will last as long as the cells fuel source. Doing this we can manufacture super batteries. The industry does not do want this because it will lose money. In fact, we can build a better primary battery cell if we use a super depolarizer. The solution is quite simple. Use a dense element like lead as your oxygen carrier.

    Will oxidized lead work as a depolarizer? Yes, it will. In fact, it works so well that it was used in zinc cells around 1887 that powered electric trolley cars in New York City. Hmmm, Tesla invents his electric car ten years later powered by "special zinc batteries." Is there a connection here?



    Lead-acid batteries should be connected to the charger _______ the power is applied.

    For the blank I put: before.

    Is that right? YES

    Because there may be hydrogen gases coming out of the battery you aren't aware of and when you hook up the after the charger is on you could create a spark and BOOM!


    Another good question the book had was

    Which combination of cells should be used for a heavy load?
    a. series <------- High voltage lower current
    b. parallel. <------- Lower voltage but higher current
    I said both. Mainly because if its heavy it will probably need lots of electrolyte from the battery and need to sustain a good current.

    Is that right? not both answer is b. parallel
     
  5. pebe

    AAC Fanatic!

    Oct 11, 2004
    628
    3
    The question is ambiguous and both answers could be correct.

    If the question refers to an existing circuit and load, then you cannot connect the cells in series because the voltage would be too high for the load. So the answer would be b. parallel.

    If on the other hand, you were designing for a new application, then connecting cells in series would be the answer. That arrangement would require less current to the load with lighter connecting cables and switch. That is the reason why the battery voltage in cordless drills has gone up over the years from 6V initially, to around 18v now.
     
Loading...