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Really confused about Physics paper question (OCR) Watch

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    In this paper, Q2 (a) (ii):

    http://www.ocr.org.uk/images/58130-q...nd-photons.pdf


    Surely the answer is that negative ions move to the positive terminal of the battery?

    The mark scheme and examiner report both say that it is positive ions.
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    Inside the battery, the positive terminal is positive because positive charges are being pushed onto it. The negative terminal, similarly, is negative because negative charge is being deposited there by the chemical reactions taking place in the electrolyte. This is how a battery works.

    You are thinking about what happens outside in the circuit.
    Outside, the negative charges that have been deposited and have collected on the negative terminal flow around to the positive terminal if there is a circuit connection that lets them.

    So the system is
    -charges inside get pushed onto the terminals (energy provided by the battery)
    -charges flow from terminals around the circuit back to the battery where they get pushed back onto the opposite terminal to go round again.
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    Okay thank you.

    It's just very confusing because my notes and book say in electrolytes the charge carriers are ions. Positive ions are attracted to the negative electrode and negative ions to the positive electrode, and this is all it has about electrolytes and ions.

    So I don't know how we are expected to know that it works like this in a battery?
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    (Original post by Mule)
    Okay thank you.

    It's just very confusing because my notes and book say in electrolytes the charge carriers are ions. Positive ions are attracted to the negative electrode and negative ions to the positive electrode, and this is all it has about electrolytes and ions.

    So I don't know how we are expected to know that it works like this in a battery?
    Well that's true.

    Whatever chemical reactions take place, the general principle of electrons going around the outer circuit and ions flowing in the opposite direction through the electrolyte happens in all batteries.

    Have a look at this. explains it in clear and concise terms:

    http://www.explainthatstuff.com/batteries.html
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    (Original post by Mule)
    Okay thank you.

    It's just very confusing because my notes and book say in electrolytes the charge carriers are ions. Positive ions are attracted to the negative electrode and negative ions to the positive electrode, and this is all it has about electrolytes and ions.

    So I don't know how we are expected to know that it works like this in a battery?
    You are confusing two different situations.

    The case where "positive ions are attracted to the negative electrode" is for when you apply an external pd to the solution. Eg connect an external battery across a copper sulphate solution. This is not a battery.

    The case of a battery is totally different. Here, the chemical reactions inside the battery (in the solution) move charges to the terminals. The terminals become "charged" as a result.
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    ITS always from positive to negative
 
 
 
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