BPSC ASSISTANT ENGINEER ELECTRICAL PAST PAPER 2025
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
- 8.5 C
- 5.5 C
- 6.5 C
- None of these
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Explanation
Q = ∫[1,2] i dt = ∫[1,2] (3t² - t) dt
= [t³ - t²/2] from 1 to 2
= (2³ - 2²/2) - (1³ - 1²/2)
= (8 - 2) - (1 - 0.5)
= 6 - 0.5
= 5.5 C
- Q < 0
- Q > 1
- Q > 0
- None of these
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Explanation
Capacitors supply reactive power to the circuit, which is considered positive in standard convention.
This helps improve power factor by compensating for inductive loads.
- The movable plates half overlap the fixed plates
- The movable plates are most widely separated from the fixed plates
- Both sets of plates are exactly meshed
- None of these
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Explanation
Capacitance is maximum when the overlapping area between movable and fixed plates is greatest.
In a variable air capacitor, this occurs when the plates are fully aligned or exactly meshed.
- 5kV - 10kV
- 13kV - 30kV
- 13kV - 60kV
- None of these
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Explanation
Modern synchronous generators typically generate voltage in the range of 13 kV to 30 kV at the generator terminals.
Step-up transformers are then used to transmit this voltage efficiently over long distances.
- C = εA²/d
- C = εA/d
- C = εA/d²
- None of these
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Explanation
Capacitance is directly proportional to plate area (A) and dielectric permittivity (ε), and inversely proportional to plate separation (d).
This formula is fundamental for designing parallel-plate capacitors.
- Integral
- Log
- Exponential
- None of these
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Explanation
An op-amp integrator produces an output voltage proportional to the time integral of the input signal.
It is widely used in analog computation, waveform generation, and signal processing.
- j6
- j4
- j2
- None of these
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Explanation
If ω = 4 rad/s:
XL = j(4)(0.5)
= j2 Ω
- 15 h
- 8 h
- 10 h
- None of these
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Explanation
Rating: 50 Ah, 10 h discharge → Rated current = 50 Ah / 10 h = 5 A
Since asked current = 5 A (matches rated),
Time = Capacity / Current = 50 Ah / 5 A = 10 h
- 1 kHz
- 20 Hz
- 100 Hz
- None of these
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Explanation
f = cycles / time
= 100 cycles / 0.1 s
= 1000 Hz
= 1 kHz
- 8000 MW
- 800 MW
- 4000 MW
- None of these
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Explanation
Pakistan’s first HVDC transmission line (Matiari‑Lahore ±660 kV) is designed to transmit up to 4,000 MW of power.
This high‑capacity link helps evacuate bulk generation from the south to load centers in the north efficiently.