. . . Mutual Inductance measurement by Heaviside Bridge . . This bridge (Fig.1) measures mutual inductance in terms of a known self-inductance. The same bridge, slightly modified, was used by Campbell to measure a self-inductance in terms of known mutual inductance.                                            Fig. 1. Heaviside mutual inductance bridge Let , M= unknown mutual Inductance , L1= self-inductance of secondary of mutual inductance , L2= known self-inductance  , R1, R2, R3, R4= non inductive resistors, At balance voltage drop between b and c must equal the voltage drop between d and c. Also the votage drop across a-b-c must equal the voltage drop across a-d-c. Thus we have the following equations at balance. $\dpi{100} \fn_jvn I_1R_3=I_2R_4$ and, $\dpi{100} \fn_jvn (I_1+I_2)jwM+I_1(R_1+R_3+jwL_1)=I_2(R_2+R_4+jwL_2)$ ..$\dpi{100} \fn_jvn \dpi{100} \fn_jvn (I_1+I_2)jwM+I_1(R_1+R_3+jwL_1)=I_2(R_2+R_4+jwL_2)\\ \therefore I_2(\frac{R_4}{R_3}+1)jwM+I_2\frac{R_4}{R_3 }(R_1+R_3+jwL_1)=I_2(R_2+R_4+jwL_2)\\ or, (\frac{R_4}{R_3}+1)jwM+\frac{R_4}{R_3 }(R_1+R_3+jwL_1)=(R_2+R_4+jwL_2)\\$ Thus,  $\dpi{100} \fn_jvn R_1=\frac{R_2}{R_3}{R_4} ..................................... (1)$ and, $\dpi{100} \fn_jvn M=\frac{L_2-L_1\frac{R_4}{R_3}}{\frac{R_4}{R_3}+1}$ $\dpi{100} \fn_jvn \therefore M=\frac{R_3L_2-R_4L_1}{R_3+R_4} ......................(2)$ It is clear from Eqn. (2), that L1, the self inductance of the secondary of the mutual inductor must be known in order that M be measured by this method. In case, R3=R4, we get,  $\dpi{100} \fn_jvn M=\frac{L_2-L_1}{2} ..............(3)\\ and, R_1=R_2......................(4)$  This method can be used for measurement of self-inductance.      Cite this Simulator:iitkgp.vlab.co.in,. (2015). Mutual Inductance measurement by Heaviside Bridge. Retrieved 27 May 2018, from iitkgp.vlab.co.in/?sub=39&brch=124&sim=1750&cnt=1 ..... ..... .....