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    I've been reading about Kirchhoff's laws and had a little trouble with this problem:

    I cant seem to get a coherent set of equations.
    any help would be much appreciated
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    you can calculate the PD across the 7 ohm external resistor in both cases...

    cells in series
    2E=2.331 + 2*r*0.311 [1]

    cells in parallel
    E=2.625 + 0.5*r*0.375 [2]

    solve as simultaneous equations to get a value for r then sub back into either [1] or [2]
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    (Original post by 123Master321)
    I've been reading about Kirchhoff's laws and had a little trouble with this problem:

    I cant seem to get a coherent set of equations.
    any help would be much appreciated
    Kirchhoff's laws might not be necessary in this question.
    For series,
    2E = I ( 2r + 7 )

    For parallel,
    E = I ( r/2 + 7)
    Note: effective emf for parallel batteries will be just emf of one battery.
 
 
 
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