A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A from 220V supply. The speed of the machine as a motor will be

A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A from 220V supply. The speed of the machine as a motor will be

(A) 800 rpm.
(B) more than 800 rpm.
(C) less than 800 rpm. 
(D) both higher or lower than 800 rpm.

Explanatory answer:

In generator

Ng= Eg (60A / FPZ) 

Eg = V + Ia Ra 

In motor

Nm= Eb (60A / FPZ) 

Eb = V - Ia Ra 

Eg > E b for same terminal voltage 

Therefore, Ng > N m

Less than 800 rpm.