Variation on the Van Der Pauw method

[evilmonkey820]

First time on this forum, hoping you can help clear something up for me.

I am using the Van der Pauw method to characterize the sheet resistance of a metal film. In the standard setup, current is pushed through two contacts and voltage is measured across the other two contacts. My colleagues are insisting that reversing this setup, pushing a voltage and measuring a current, will produce the same results. But they haven't been able to explain why. Wouldn't this create a current divider? The measured current wouldn't be the same as the current crossing the square.

I haven't been able to find any sources supporting this and they haven't been able to give me any. I'm also worried that since my films have a very low 2 pt probe resistance, the low impedance of the ammeter would add an error to the measurement.

Any help clearing this up would be appreciated.

 

[anorlunda]

Try https://en.wikipedia.org/wiki/Linear_motor

Specific questions such as "how strong should the magnet be" can not be answered unless you specify the requirements of the motor. How much liner force? How much power?

If you want only approxiate numbers, borrow them from ordinary electric motors. A linear motor is nothing more than a rotating motor flattened out. The basic electric and magnetic quantities don't change much by flattening.

 

[The Electrician]

Anorlunda seems to be responding to a different thread.

The behavior described by your colleagues is a consequence of the reciprocity theorem:

http://www.electrical4u.com/reciprocity-theorem/

http://electrical-engineering-portal.com/resources/knowledge/theorems-and-laws/reciprocity-theorem

Also look under the heading "Reciprocal Measurements" and "Reversed Polarity Measurements" here:

https://en.wikipedia.org/wiki/Van_der_Pauw_method