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Internal Resistance Graph

  • Thread starter Vaseline
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  • #1
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When taking internal resistance into account, voltage/current graph has negative gradient (i.e. internal resistance).?

My thoughts...

Because for ohmic resistors, graph has a positive gradient. Why does one say that when V=0, Current = max, whilst the other says that when V=0, Current = 0?
 

Answers and Replies

  • #3
459
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When taking internal resistance into account, voltage/current graph has negative gradient (i.e. internal resistance).?

My thoughts...

Because for ohmic resistors, graph has a positive gradient. Why does one say that when V=0, Current = max, whilst the other says that when V=0, Current = 0?
My question was answered in that thread, this is the result I got.

[itex] E = I(R+r) [/itex] where R is the total resistance in the circuit and r is the internal resistance of the cell or battery. From this we can see that,

[itex] E = V + Ir [/itex]

and,

[itex] V = E - Ir[/itex]

When plotting a graph of potential different against current it is clear that the current I has a negative co-efficient: -r. Hence -r is the gradient of the line, and E is the y intercept. y=mx +c (remember?) this is just V=-rI+E.
 

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