OK, little bit understanding. Even there is no physical connection there is electrical connection. Now from the standard text book I took the sign convention of transistor here the assumption is made that all the currents flowing into the transistor are considered positive that is ok for me but regarding the voltage drops VEB, VCB, VCE. From what i understand Emitter voltage is higher than Base, but in reality if you see Base is at higher voltage than emitter by around 0.6V and sometimes 0 in cutoff which are fixed. Then why the book considers Emitter at higher voltage than base. I am not sure i am clear in my question but somehow i want to know the sign notation of voltage drops in transistors that is which terminal voltage is at which level compared to others.