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    I have done the first one, can you do the 2nd: https://isaacphysics.org/questions/r...haracteristics

    I dont even know where to begin.

    could you answer part B please.

    thanks.
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    (Original post by YourGoddamnRight)
    I have done the first one, can you do the 2nd: https://isaacphysics.org/questions/r...haracteristics

    I dont even know where to begin.

    could you answer part B please.

    thanks.
    P = VI

    the current through both the resistor and LED is the same (because they're in series)

    ...so the ratio of powers is the same as the ratio of voltages.

    FWIW
    The real life application of this is that it's impractical to use resistors in series with LED's across high voltage supplies e.g. LED lightbulbs connected to 230V mains and you have to find some other way of limiting the current
 
 
 
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