Why open loop transfer function ?

[reddvoid]

I don't understand why always we use open loop transfer function G(s)H(s) to draw the root locus.
can somebody please clarify my doubt.




Thanks in advance.

 

[dummie]

because G(s)H(s) is easily available in factor form as it is obtained by simply modelling the transfer functions of individual components and multiplying them . this helps in obtaining the poles and zeroes easily as opposed to closed loop transfer function whose roots are hard to find.