he unknown resistance S = R will be equal to the third arm resistance. If the deflection is not made zero, then due to the two successive resistances the deflection will be opposite. In this situation, the value of the unknown resistance S is between these values.
(iv) Now in arm P instead of 10 ohms, 100-ohm resistances are inserted. As before the resistance of the second arm, Q is kept at 10 ohms. So Q/P ratio will be 1/10, hence in balanced condition R = 10 S. Now as before resistance plugs from the third arm R are withdrawn so that galvanometer deflection becomes zero. In this situation, unknown resistance S = R/10.
(v) Similarly, 1000 ohm resistance is inserted in arm P and in Q arm 10-ohm resistance is inserted and the experiment is performed as before.