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    • Thread Starter

    A high resistance voltmeter records the potential difference across a battery which is connected to a variable resistor of resistance R,

    The reading on the voltmeter, V, takes the following values: V=V𝟢 when R=R𝟢 and V=V𝟣 when R=R𝟣,

    calculate the internal resistance r

    I presume you are being asked to derive the equation for internal resistance from V𝟢 R𝟢 V𝟣 R𝟣,
    Internal resistance of a battery is imagined as a resistor in series with the battery. So using Ohms law and equation for resistors in series, r can be calculated.
    • Thread Starter

    yes, but I cant seem to get the right answer when doing this

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