Electrical Engineering Questions and Answers


66)

To tune a parallel resonant circuit to a higher frequency, the capacitance should be

Answer: Option B

Explanation:

Because fr=1/(2*pi*root(LC)).
67)

A 24 Ω resistor, an inductor with a reactance of 120 Ω, and a capacitor with a reactance of 120 Ω are in series across a 60 V source. The circuit is at resonance. The voltage across the inductor is

Answer: Option D

Explanation:

As in resonace impedance equal to resistance
Current = 60/24 = 2.5
Vtg across inductor = 120*2.5 = 300V
68)

If the value of C in a series RLC circuit is decreased, the resonant frequency

Answer: Option B

Explanation:
69)

A resonant circuit has a lower critical frequency of 7 kHz and an upper critical frequency of 13 kHz. The bandwidth of the circuit is

Answer: Option D

Explanation:

B.W = f2-f1.
B.W = 13-7 = 6.
70)

A 90 Ω resistor, a coil with 30 Ω of reactance, and a capacitor with 50 Ω of reactance are in series across a 12 V ac source. The current through the resistor is

Answer: Option D

Explanation:

V=IR
I=V/R
So.. R is nothing but Z (R=Z)
Z=sqrrt(R^2+( xl-xc)) OR (R^2+(xc-xl))
z=sqrrt_(90^2+(50-30^2)
Z=SQRRT(8100+400)
z=92.195
I=V/Z=12/92.195=0.13015=130mA.

 

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