GATE 2021 EE question paper PDF and answer key

The vertical stroke of the K lies left of the fold, while both arms cross it. Folding the right half over the left mirrors the parts of the arms beyond the fold. Each arm now meets the fold line at a point and goes back to the left twice: once to the stroke (original part) and once outward (mirrored part). This gives the two right-pointing wedges touching the fold, as in (C).

The passage says lack of sleep hurts recall, so cutting sleep is counterproductive: adequate sleep must be part of the preparation (D). The other options go beyond or against the passage.

Open circuit: no current flows in the 2 Ω, so $i_1 = 5$ A and the 10 Ω carries 50 V. Adding the dependent source $3i_1 = 15$ V gives $V_{th} = 50 + 15 = 65$ V.

Test source: with the 5 A source removed, inject $I$ at a. Then $i_1 = I$ and $V = 2I + 3I + 10I = 15I$, so $R_{th} = 15\ \Omega$.

• Damper bars are used in synchronous machines against hunting (P-U-X).
• Skewed rotor slots are used in induction motors against magnetic locking (cogging) (Q-S-Y).
• Compensating windings are used in DC machines to neutralise armature reaction (R-V-Z).

$I = 0$ needs the load after the series $10\ \Omega + j5\ \Omega$ to be an open circuit. So the shunt $j5\ \Omega$ must be in parallel resonance with the branch $j5 - jX_C$:

$j5 + j5 - jX_C = 0$, so $X_C = 10\ \Omega$ and $C = \frac{1}{5000 \times 10} = 20\ \mu F$.