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A
XL = Xc
B
Power factor unity
C
minimum impedence
D
সবকয়টি

Explanation

In an RLC series resonant circuit, the inductive reactance equals the capacitive reactance (XL = Xc), resulting in minimum impedance (Z = R) and a unity power factor, which allows maximum current flow.

A
provides high starting torque
B
provied fine speed control
C
has simple and rugged construction
D
none of the above

Explanation

Induction motors are generally preferred over DC motors because they have a simple and rugged construction (no brushes or commutators), require less maintenance, and are more robust in harsh environments.

A
Mica
B
varnish
C
porcelain
D
Teflon

Explanation

Porcelain is the most common material used for insulators in overhead transmission lines due to its high dielectric strength, mechanical durability, and resistance to environmental elements like rain.

A
R1 = 2R2
B
R2 = 2R1
C
R2 = 4R1
D
R1 = 4R2

Explanation

Since power P = V²/R, resistance is inversely proportional to power at constant voltage. The 100W bulb has half the power of the 200W bulb, so its resistance (R2) will be double the resistance (R1).

A
বাড়ে
B
কমে
C
একই থাকে
D
কোনোটিই নয়

Explanation

Wavelength is inversely proportional to frequency (λ = v/f). Therefore, as the frequency of a signal increases, its wavelength decreases, assuming the velocity of the wave remains constant.

A
watt
B
HP
C
KW-h
D
Tons

Explanation

The cooling capacity of air conditioners is commonly measured in Tons. One Ton of refrigeration is equivalent to the cooling power required to freeze one ton of water into ice in 24 hours (approx 12,000 BTU/hr).

A
Cu loss
B
hysteresis loss
C
eddy current loss
D
core loss

Explanation

Laminated cores are used in transformers to reduce eddy current losses. The laminations insulate small sections of the core from each other, increasing resistance to the flow of eddy currents.

A
1.44
B
1.11
C
2
D
1.5

Explanation

The form factor is the ratio of the RMS value to the average value. For a sinusoidal wave, RMS is 0.707 and Average is 0.637 of the peak, giving a ratio of approximately 1.11.

A
Primary draws small current
B
Primary leakage resistance is increased
C
Core losses are increased
D
Primary may burn out

Explanation

DC supply has zero frequency, so there is no inductive reactance (XL=0). The primary winding offers only very low resistance, causing excessive current to flow, which may burn out the winding.

A
Resistance
B
Inductance
C
Capacitance
D
সবকয়টি

Explanation

Bridge circuits (like Wheatstone, Maxwell, etc.) are versatile tools used to measure various electrical parameters including resistance, inductance, and capacitance with high precision.