 #1
 438
 0
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 copperconstantan 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 .
Attachments

175 KB Views: 491