Well *externally* distinguishing a Medha & Bombardier is out of my knowledge. Anyways we have an "assumption". To understand,read as follows
ЁЯФ╕Kolkata EMUs operate in Howrah div,Sealdah div & Kharagpur div only. All these divisions have received 3PH EMU Rake. HWH & KGP div only operate Medha 3PH EMUs while SDAH div has complete Bombardier stock.
ЁЯФШLets come to externally distinguishing feature ASSUMED by us
.......
more... According to observations,
ЁЯФ╕Bombardier EMUs make no rythimic sound during accleration/deceleration (Video No.1,listen from 01:30 to 01:50)
ЁЯФ╕Medha EMUs make a rythimic sound (Video No.2 , carefully listen from 01:18 to 01:23)
.
ЁЯФШAgain,this is just an assumption ... Others may highlight if knwon.