That allows us to do the substitution in the second last equation to get the final equation solving for Lx, shown in the diagram. With this used for a Wheatstone bridge, we first have to balance ...

[Keri] selects them not with his golden ears, but by wiring both pots together as a Wheatstone bridge. A meter between the two wipers would detect any current due to a mismatch. A Wheatstone ...