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What are the differences between positive and negative feedback loops? watch

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    What are the differences between positive and negative feedback loops?

    I keep on getting confused over them
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    (Original post by Blueray2)
    What are the differences between positive and negative feedback loops?

    I keep on getting confused over them
    I'm not definitely sure myself, but this is what I believe they are:
    An event occurs (such as more CO2 being in the air) > this results in another event (say Earth gets warmer because of the CO2) > this 2nd event increases/accelerates the first event (warmer Earth = more vegetation = more CO2 produced = Earth gets warmer = more vegetation etc.)
    So it is a positive feedback loop/cycle

    Negative feedback is the opposite.
    An event occurs (such as warming of the Earth) > this results in another event (such as the evaporation of water to form water vapour in the air) > this 2nd event decreases/reduces the effects of the first event (more water vapour in the air = more clouds = more of the Sun's rays are reflected back by the clouds so the Earth does not get warmer)

    Hope the analogies help ^^
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    Negative feedback tends to keep things constant. The level of one thing increases and is counteracted by another, bringing it back to it's normal level.

    Positive feedback usually occurs when something increased rapidly. This often happens when Thing A leads to an increase of Thing B and then Thing B causes A to increase, therefore causing B to increase, causing A to increase etc. It amplifies a change.
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    (Original post by PhysicsGal)
    I'm not definitely sure myself, but this is what I believe they are:
    An event occurs (such as more CO2 being in the air) > this results in another event (say Earth gets warmer because of the CO2) > this 2nd event increases/accelerates the first event (warmer Earth = more vegetation = more CO2 produced = Earth gets warmer = more vegetation etc.)
    So it is a positive feedback loop/cycle

    Negative feedback is the opposite.
    An event occurs (such as warming of the Earth) > this results in another event (such as the evaporation of water to form water vapour in the air) > this 2nd event decreases/reduces the effects of the first event (more water vapour in the air = more clouds = more of the Sun's rays are reflected back by the clouds so the Earth does not get warmer)

    Hope the analogies help ^^
    Hmm so a positive feedback is like
    1 effect leads to a another worse off effect (so its bad?)

    Negative feedback
    1 effect leads to an effect which lessens the impact of the effect (so its good?)
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    (Original post by luke2511)
    Negative feedback tends to keep things constant. The level of one thing increases and is counteracted by another, bringing it back to it's normal level.

    Positive feedback usually occurs when something increased rapidly. This often happens when Thing A leads to an increase of Thing B and then Thing B causes A to increase, therefore causing B to increase, causing A to increase etc. It amplifies a change.
    So my stuff above this is wrong?

    And well said
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    (Original post by Blueray2)
    Hmm so a positive feedback is like
    1 effect leads to a another worse off effect (so its bad?)

    Negative feedback
    1 effect leads to an effect which lessens the impact of the effect (so its good?)
    I know this is the geography forum but I don't do this subject (seen it in 'latest discussions')

    In Biology, an example of a positive feedback loop would be in the menstrual cycle; Oestrogen concentration increases to a high level, which means it stimulates the releases of the hormones FSH and LH. In turn, LH stimulates the ovaries to release more oestrogen – which causes the release of more LH. (This causes more oestrogen to be released, and so on). Therefore because Oestrogen has increased, the amount of LH has increased. Because there is more LH, more oestrogen is produced, which causes more LH to be produced -> So the amount of oestrogen is constantly increasing.

    Negative feedback is seen in the control of body temperature. When the temperature gets too high, thermo-receptors detect this and send electrical signals to the hypothalamus. This causes sweating and other measures to cool the body down so that it returns to it's normal level. Therefore negative feedback stops the temperature getting too high and brings it back to it's 'constant' state.

    Sorry I can't provide any geography-specific analogies!

    And unless it's different in geography, I'd say your wrong. I'm just presuming this is a general concept.
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    (Original post by Blueray2)
    Hmm so a positive feedback is like
    1 effect leads to a another worse off effect (so its bad?)

    Negative feedback
    1 effect leads to an effect which lessens the impact of the effect (so its good?)
    (Original post by Blueray2)
    So my stuff above this is wrong?

    And well said

    I think you've got it (re good = neg, & pos = bad) but I'm not too sure, but what the other poster said is an ace explanation ^^
 
 
 
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