Check that the meter bridge wire is connected. If not, just connect both ends of the wire tightly. The apparatus has 5 places for the connections. All gaps for connections are found above the meter bridge wire; two on either sides and one in the middle.
Imagine 5 dots plotted on a paper which are coplanar also imagine a line below it which is a little longer than the line which we can get if we join the points. The above connection is similar to this.
Connect a known resistance on one side and unknown resistance on the other this fills 4/5 gaps left for connections. In the remaining gap, connect a galvanometer, high resistance and jockey all in series.
Slide the jockey over the meter bridge wire and note down the reading for which you get zero deflection in galvanometer.
Let it be R1 now put R2=100-R1.
Similarly, calculate another reading by interchanging the known and unknown resistances in the above circuit.
Let the new readings be R3 and R4 where R3 is the length obtained for zero deflection and R4=100-R3.
Add R1 and R3 and divide it by two. note it down as L. calculate the average for R2 and R4 too let it be M.
Repeat the above for various known resistance values. Each time you can calculate the unknown resistance using the formula:unknown resistance(a)=known resistance(b)*L/M. The value is found to be the same for all values of known resistance.
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