Correct Answer:- Option-C

Question21:-The maximum efficiency occurs in a separately excited generator when
the terminal voltage is 220 V and the induced EMF is 240 V. The armature
resistance is 2 ohm. The stray losses of the machine is

A:-100 W
B:-200 W
C:-244 W
D:-188 W
Correct Answer:- Option-B

Question22:-The full load copper loss and iron loss of a transformer are 6400 W and
5000 W respectively. The copper loss and iron loss at half load will be, respectively

A:-1600 W and 5000 W
B:-3200 W and 2500 W
C:-1600 W and 1250 W
D:-3200 W and 5000 W
Correct Answer:- Option-A

Question23:-What is the frequency of rotor current of a 50 Hz induction motor
operating at 2% slip?

A:-50 Hz

B:-25 Hz

C:-2 Hz

D:-1 Hz

Correct Answer:- Option-D
Question24:-The condition for maximum efficiency of a DC Machine

A:-Core loss = Copper loss

B:-Constant loss = Variable loss

C:-Rotational losses = Copper loss

D:-Core loss = Half of Copper loss

Correct Answer:- Option-B

Question25:-A 200 V DC shunt motor develops a torque of 54 N-m at an armature
current of 10A. The torque produced when armature current is 20 A, is

A:-108 N-m

B:-54 N-m

C:-216 N-m

D:-27 N-m

Correct Answer:- Option-A

Question26:-A 400/200V, 5 KVA transformer has a core loss of 200 W and a full load
copper loss of 800 W. The load at which maximum efficiency occurs is