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We have a simple circuit given, a resistor $R_x$ and a fixed current source with $I = 50 \, \mathrm{\mu A}$. Now over the resistor there is a currentmeter which has an internal resistance. In any case some of the current will go through the currentmeter and therefore the result will be slightly off.

The question asks us to rearrange that circuit so that no measurement error is made. We can use additional parts like a power source or a resistor with variable resistance or anything else.

Is there some way to do this other than using a currentmeter with a higher internal resistance?

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up vote 3 down vote accepted

Use Wheatstone bridge:

This is classical way of measuring resistivities with no error due to imperfectness of measurement instruments (e.g. galvanometer).

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Thanks, that is a sweet trick :-) – Martin Ueding May 20 '12 at 18:07

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