Apparatus: Fig. 2 shows the schematic diagram for your experiment.
The 33-ohm resistor used as a voltage divider allows you to vary the voltage applied to the circuit, and hence the sensitivity of the bridge. ( How do you define sensitivity and how does it change as the applied voltage changes?) Resistor Rp=1000 Ohms with tap switch in parallel is used to protect the galvanometer. You will have calibrated resistors 15 Ohms and 50 kOhms to use as Rs.