A sinusoidal voltage V and frequency f is connected to a series circuit at variable resistance R and a fixed reactance X. The locus of the tip of the current phasor I as R is varied from 0 to ∞ is

1.  a semicircle with a diameter V/X

2.  a straight line with a slope R/X

3.  an ellipse with V/R as major axis

4.  a circle at radius R/X and origin at (0,V/2)

4

a semicircle with a diameter V/X

Explanation :
No Explanation available for this question

A circuit with a resistor , inductor and capacitor in series is resonant of f0 Hz . If all the component values are now doubled , the new resonant frequency is

1.  2 f0

2.  Still f0

3.  f0/2

4.  f0/4

4

f0/2

Explanation :
No Explanation available for this question

A periodic rectangular signal X(t) has the wave form shown in the figure . Frequency of the fifth harmonic of its spectrum is

1.  40 Hz

2.  200 Hz

3.  250 Hz

4.  1250 Hz

4

1250 Hz

Explanation :
No Explanation available for this question

In the series RC circuit shown in the figure , the voltage across C starts increasing when the d.c. source is switched on. The rate of increase of voltage across C at the instant just after the switch is closed (i.e. at t = 0+ ) will be

1.  Zero

2.  Infinity

3.  RC

4.  1/RC

4

1/RC

Explanation :
No Explanation available for this question

In the network shown in the figure , the circuit was initially in the steady – state condition with the switch K closed . At the instant when the switch is opened , the rate of decay of current through the inductance will be

1.  Zero

2.  0.5 A/s

3.  1 A/s

4.  2 A/s

4

2 A/s

Explanation :
No Explanation available for this question

In the circuit shown in the figure , the switch S has been opened for long time . It is closed at t = 0.For t > 0 , the current flowing through the inductor will be given by

1.  iL (t) = 1.2 + 0.8 e-2t

2.  iL (t) = 0.8 + 1.2 e-2t

3.  iL (t) = 1.2 - 0.8 e-2t

4.  iL (t) = 0.8 + 1.2 e-2t

4

iL (t) = 1.2 + 0.8 e-2t

Explanation :
No Explanation available for this question

After closing the switch ‘S’ at t = 0 , the current i(t) at any instant ‘t’ in the network shown in the given figure will be

1.  10 + 10 e100t

2.  10 - 10 e100t

3.  10 + 10 e-100t

4.  10 - 10 e-100t

4

10 - 10 e-100t

Explanation :
No Explanation available for this question

For the series R-L-C circuit of Fig.(a), below the partial phasor diagram at a certain frequency is shown in Fig.(b). The operating frequency of the circuit is

1.  Equal to the resonance frequency

2.  Less than the resonance frequency

3.  Greater than the resonance frequency

4.  Not zero

4

Greater than the resonance frequency

Explanation :
No Explanation available for this question

For the compensated attenuator of figure below , the impulse response under the condition R1C1 = R2C2 is

1.

2.

3.

4.

4

Explanation :
No Explanation available for this question

1.  200 < -900

2.  200 < +900

3.  400 < +900

4.  400 < -900

4