Electrical Engineering questions for GATE, PSU recruitment and SSC JE draw from network theory, electrical machines, power systems, control systems, measurements and instrumentation, analog and digital electronics, and electromagnetic fields. Numerical answers include the formula used and the unit at each stage, which is where marks are commonly lost even when the approach is correct.
In a transformer, the hysteresis loss depends on which of the following factors?
Answer: B
Hysteresis loss = η × B^1.6 × f × V, where η is Steinmetz constant, material property is crucial
Q.62Easy
A 3-phase induction motor has 4 poles and operates at 50 Hz. What is the synchronous speed?
Answer: B
Ns = 120f/P = 120×450 = 1500 rpm
Q.63Easy
What is the typical slip value for a squirrel-cage induction motor operating at full load?
Answer: B
Full load slip for squirrel-cage motors typically ranges from 3-5% for good efficiency
Q.64Hard
In a synchronous generator, the voltage regulation is negative when:
Answer: A
Leading power factor means reactive component opposes armature reaction, reducing terminal voltage drop
Q.65Medium
A series DC motor is suitable for which of the following applications?
Answer: B
Series motors develop very high starting torque, ideal for electric vehicles and heavy-duty applications
Q.66Medium
The open-circuit test on a transformer primarily helps to determine:
Answer: A
OC test measures core loss (hysteresis + eddy current) and magnetizing component of no-load current
Q.67Medium
In a permanent magnet synchronous motor (PMSM), the torque is primarily developed due to:
Answer: A
PMSM torque = Pm × Is × sin(δ), where Pm is permanent magnet flux and Is is stator current
Q.68Hard
For a 3-phase synchronous motor connected to infinite bus, increasing field excitation beyond the critical value will:
Answer: B
Over-excitation reduces armature current by creating leading reactive component that cancels lagging current
Q.69Hard
The cogging torque in a DC motor is primarily due to:
Answer: A
Cogging torque results from interaction between poles and armature teeth, causing reluctance variation
Q.70Hard
A 3-phase induction motor develops maximum torque at a slip of 0.4. The motor is operating at slip 0.1. What is the ratio of starting torque to running torque?
Answer: D
Using slip relationship, Ts/T = (smax/s)² = (0.04.1)² = 16 for normal induction motor characteristics
Q.71Medium
In a wound-rotor induction motor, adding external resistance to the rotor circuit:
Answer: A
External rotor resistance shifts the point of maximum torque to higher slip values
Q.72Medium
The commutation in a DC machine is said to be 'overcommutated' when:
Answer: B
Over-commutation occurs when induced EMF > required EMF, causing sparking at trailing edge of brushes
Q.73Easy
A transformer has primary turns = 1000, secondary turns = 100. If primary current is 2 A, what is the secondary current (neglecting losses)?
Answer: C
Using transformer equation: Np/Ns = Is/Ip; 1001000 = Is/2; Is = 20 A
Q.74Medium
In an induction motor, the torque under running conditions is proportional to:
Answer: C
T ∝ Ir × cos(φr) × r/s, where torque depends on rotor current magnitude and its power factor
Q.75Medium
Which of the following represents the condition for maximum power transfer in a DC generator connected to external load?
Answer: A
Maximum power transfer theorem: Load resistance equals source resistance for maximum power output
Q.76Hard
A synchronous generator operating at leading power factor supplies current to an infinite bus. This condition represents:
Answer: A
Over-excitation produces leading current (capacitive), supplying reactive power to the bus
Q.77Hard
The crawling phenomenon in induction motors occurs due to:
Answer: B
Crawling results from 5th, 7th harmonics creating torques at different slip values, causing low-speed oscillations
Q.78Medium
In a 3-phase transformer with Y-Δ connection, the secondary voltage lags the primary by:
Answer: B
Y-Δ connection introduces 30° phase shift with secondary lagging primary voltage phasor
Q.79Medium
For a DC shunt motor operating at rated conditions, if the load is suddenly increased, the motor will:
Answer: B
Increased load increases Ia, causing larger voltage drop (IaRa), reducing back EMF and speed until new equilibrium
Q.80Medium
A DC series motor is used in electric trains. If the load torque decreases suddenly, what happens to the motor speed?
Answer: A
In a DC series motor, as load decreases, back EMF increases relative to applied voltage, causing field current to reduce. This results in a significant increase in motor speed.
