 Maxwell bridge

A null electrical circuit for measuring a lossy inductor against a standard capacitor. If opposite arms are $R_x+i\omega L_x$ and $(1/R_1+i\omega C{)}^{-1}$, and the remaining arms are $R_2,R_3$, balance requires their products to agree. Consequently $R_x=R_2{R}_3/R_1$ and $L_x=C{R}_2{R}_3$. Two independent real adjustments are necessary; changing the source frequency does not change the ideal balance conditions.