A potentiometer wire PQ of 1m length is connected to a standard cell E1. Another cell E2 of emf 1.02 V is connected with a resistance 'r' and switch S (as shown in figure). With switch S open, the null position is obtained at a distance of 49 cm from Q. The potential gradient in the potentiometer wire is :
(1) 0.01 V/cm
(2) 0.04 V/cm
(3) 0.03 V/cm
(4) 0.02 V/cm