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## Homework Statement

The slide wire of a simple potentiometer has a resistance of 5.0 ohm . The current source for the potentiometer is a cell of emf of 2.0V and of negligible internal resistance . Draw a labelled circuit diagram showing how the potentiometer might be used to measure an emf of up to about 2.5 mV from a copper-constantan thermocouple . Calculate a suitable value for the resistor which should be placed in series in the slide wire .

## Homework Equations

## The Attempt at a Solution

I have drawn a diagram (attached) . Let resistance of the resistor be R .

the pd across AJ = pd of thermocouple

[tex]\frac{2}{R+5}(R)=2.5\times 10^{-3}[/tex]

solving that doesn't lead me to the answer .

maybe i made a mistake in calculating the resistance of AJ , do i have to add the resistance of the wire as well , or the resistance is simply R .