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A
25
B
50
C
78.5
D
60

Explanation

The maximum theoretical efficiency of a Class-B push-pull power amplifier is π/4, which is approximately 78.5%. This is higher than Class-A but lower than Class-C amplifiers.

A
kVA
B
KVAR
C
HP
D
kW

Explanation

Alternators are rated in kVA (Kilovolt-Amperes) rather than kW because their heating and losses depend on the total current (Apparent Power), not just the active power, which varies with the power factor.

A
infinite
B
zero
C
very small
D
কোনোটিই নয়

Explanation

A superconductor is a material that can conduct electricity with zero electrical resistance below a certain critical temperature, meaning its conductivity is effectively infinite.

A
Negative
B
Positive
C
Zero
D
কোনোটিই নয়

Explanation

Semiconductors have a negative temperature coefficient of resistance. As temperature increases, more charge carriers are generated, which decreases the resistance, unlike metals where resistance increases.

A
Zero
B
Unity
C
Leading
D
Lagging

Explanation

In Direct Current (DC) circuits, the frequency is zero, so there is no phase difference between voltage and current. Consequently, the power factor is always unity (1).

A
rms
B
maximm
C
average
D
peak-to-peak

Explanation

Standard AC ammeters and voltmeters are calibrated to measure the RMS (Root Mean Square) value of the alternating current or voltage, which represents the effective DC equivalent heating value.

A
কমে
B
বাড়ে
C
একই থাকে
D
কোনোটিই নয়

Explanation

Skin effect causes AC current to concentrate near the surface of the conductor, reducing the effective cross-sectional area. This reduction in effective area causes the resistance of the conductor to increase.

A
non-linear
B
bilateral
C
linear
D
কোনোটিই নয়

Explanation

A crystal diode (semiconductor diode) is a non-linear device because its current-voltage characteristic curve is not a straight line; it conducts current much more easily in one direction than the other.

A
Peak load plant
B
base load plant
C
standby plant
D
কোনোটিই নয়

Explanation

Diesel power plants can start up quickly and are typically used as peak load plants to meet sudden high demands or as standby/emergency power sources, rather than for continuous base load.

A
220 kV
B
230 kV
C
400 kV
D
33 kV

Explanation

Currently, the highest transmission voltage level in the national grid of Bangladesh is 400 kV (e.g., the Aminbazar-Meghnaghat line), upgraded from the previous 230 kV standard.