A potentiometer (with potential gradient ρ) is set up as shown. The ammeter reads 1.0 when the two way key is switched off. When the points 1, 2 of the key are connected the balance is obatined at x cm and when the points 1 and 3 are connected the balance is obatined at y cm of the potentiometer wire. Then the magnitude of the resistors R and Q are equals when respectively to ρ (y - x) and ρx.
