ASSISTANT ENGINEER ELECTRICAL PAST PAPERS YEAR 2025
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
Microgrid Controllers
Demand Side Management (DSM)
Phasor Measurement Units (PMUs)
None of these
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Explanation
DSM monitors and adjusts consumer load in real time to match supply and prevent grid stress.
It helps in efficient energy usage and maintains stability in a smart grid.
Controlled Rectifier
Inverter
Cycloconverter
None of these
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Explanation
Controlled rectifiers (like SCR-based converters) convert AC to DC with adjustable output by controlling firing angles.
They are widely used where variable DC voltage is needed from an AC supply .
Pulse Width Modulation (PWM)
Phase-angle control
Linear voltage regulation
None of these
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Explanation
PWM adjusts the duty cycle of the switching device to maintain constant output voltage .
It provides high efficiency and precise voltage regulation in switch-mode power supplies.
To eliminate the effects of aliasing in sampled signals
To analyze and design linear time-invariant systems in the frequency domain
To convert continuous-time signals into discrete-time signals
None of these
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Explanation
Z-transform converts discrete-time signals into a complex frequency domain for analysis.
It simplifies solving difference equations and designing digital filters.
Euler’s method
Gauss-Seidel method
Newton-Raphson method
None of these
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Explanation
Newton-Raphson method converges rapidly even for large, complex power systems.
It uses iterative linearization, making it more efficient than Gauss-Seidel for large-scale load flow analysis.
It minimizes fault currents
It eliminates the need for protective relays
It ensures continuous operation
None of these
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Explanation
High-impedance grounding limits the current during ground faults, protecting equipment.
It reduces damage and arc flash hazards while allowing system operation to continue.
It requires an external regulator to maintain field excitation
Its torque decreases
Its speed varies widely with changes in load
None of these
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Explanation
In a series-wound DC motor , the field winding is in series with the armature, so flux depends on load current .
As load changes, flux changes → speed changes significantly , making it unsuitable for constant-speed applications.
The armature current will drop to zero.
The motor will stop.
The motor speed will increase uncontrollably.
None of these
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Explanation
In a DC shunt motor , the field winding provides the magnetic flux; if it opens, flux drops sharply.
With reduced flux, back EMF decreases, causing the armature to accelerate , leading to uncontrolled speed (dangerous condition).
Carrier frequency
Amplitude of the modulating signal
Frequency deviation and the highest frequency of the modulating signal
None of these
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Explanation
In FM , the bandwidth depends on how much the carrier frequency varies (frequency deviation) and the maximum frequency present in the modulating signal.
Carson’s rule is commonly used to estimate the total FM bandwidth as twice the sum of frequency deviation and modulating frequency .
Short-circuit the output.
Measure the total resistance of the circuit.
Remove the load resistor and calculate the resistance seen from its terminals.
None of these
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Explanation
Thevenin equivalent resistance is found by deactivating all independent sources and measuring resistance across the open terminals where the load was connected .
This simplifies complex circuits into a single voltage source and series resistance for easier analysis.
