1
GATE EE 1998
MCQ (Single Correct Answer)
+2
-0.6
A 50 Hz transformer having equal hysteresis and eddy current losses at rated excitation is operated at 45 Hz at 90% of its rated voltage. Compared to rated operating point, the core losses under this condition:
A
reduce by 10%
B
reduce by 19%
C
reduce by 14.5%
D
remain unchanged
2
GATE EE 1998
MCQ (Single Correct Answer)
+1
-0.3
The efficiency of a 100 kVA transform is 0.98 at full as well as at half load. For this transformer at full load the copper loss.
A
is less than core loss
B
is equal to core loss
C
is more than core loss
D
none of the above
3
GATE EE 1998
MCQ (Single Correct Answer)
+2
-0.6
A 240 V d.c. shunt motor with an armature resistance of 0.5 $$\Omega$$ has a full load current of 40 A. Find the ratio of the stalling torque to the full load torque when a resistance of 1 $$\Omega$$ is connected in series with the armature?
A
4
B
12
C
6
D
None of the above
4
GATE EE 1998
MCQ (Single Correct Answer)
+1
-0.3
The laws of electromagnetic induction (Faraday's and Lenz's law) are summarized in the following equation:
A
e = iR
B
$$\mathrm e\;=\;\mathrm L\frac{\operatorname d\mathrm i}{\operatorname d\mathrm t}$$
C
$$\mathrm e\;=\;-\frac{\operatorname d\mathrm\psi}{\operatorname d\mathrm t}$$
D
none of these