An ideal battery of 6 V and resistance R are connected in series in the primary circuit of a potentiometer of length 4 m and resistance 10 Ω. The value of R, to give a potential difference of 10 mV across 20 cm of potentiometer wire is:

390 Ω 395 Ω 290 Ω 310 Ω

290 Ω

The correct answer is Option (3) → 290 Ω