Graph showing the variation of current versus voltage for a material Ga As is shown in the figure, Identify the region of:(i) negative resistance (ii) where Ohm's law is obeyed

By Ohm's law, V=IR or I=V/R Thus, the resistance is inverse of slope of graph I vs V. i) As the slope is negative for part DE so the resistance will be negative for part DE. ii) According to Ohm's law, current I is proportional to V so the part BC will obey Ohm's law.