A Wheatstone bridge is a cirCuit used for precisely measuring resistances. it consists of a voltage source. a galvanometer (used for precisely measuring small currents), three known resistors. and one unknown resistor which is to be measured. The drawing below shows a circuit diagram of a Wheatstone bridge: R1 b R2 W V\\/\\/\\/' a C Rx R3 \\A/VV' W (I Resistors R1. R2. and R3 have known values, and resistor Rx is an unknown. The G in the middle stands for galvanometer, a device used for sensitive measurement of current. The bridge is said to be balanced when the galvanometer reading is zero. When this is the case, there is no current owing through the galvanometer, and so points b and cl must be at the same potential. 1) If we let I1 be the current in the top branch of the circuit (passing through resistors 1 & 2), and la be the current in the bottom branch (passing through resistors 3 & x), show mathematically that when the bridge is balanced, Kirchoff's loop rule results in the following two equations: l'lR1 = lst and |1R2 = 13R3 2) Now show that after a little algebra. this becomes Rx/R3=R1/R2