577 + Interview Questions in Networks Analysis and Synthesis in Electronics and Communication Engineering Page 7 InterviewSolution

301.	Two similar coupled coils are connected in series. The total inductance in series aiding connection is 100 mH. If currents is 3 A, the energy stored in magnetic field is
Answer» Energy = 0.5 LI2.

Discussion

302.	The Voltage in the figure,
Answer» Req = 4 \|\| 4 + 4 6&ohm; I = 2A I = I1 + I2 1 + 1 e0 = 4 x 1 4v.

Discussion

303.	A 1 μF capacitor is connected to 12 V battery. The energy stored in the capacitor is
Answer» Energy x 1 x 10-6 x 144 = 72 x 10-6 J

Discussion

304.	The poles with greater displacement from the real axis correspond to
Answer» As distance from real axis increases, the frequency of oscillation increases.

Discussion

305.	In figure, the capacitor is charged to 1 V. At = 0 the switch is closed so that = . When = 0.37 A, the voltage across capacitor is
Answer» During discharge of capacitor vC = vR = 0.37 x 1 = 0.37 V

Discussion

306.	In the circuit of figure the current through C at = ∞ is
Answer» At t = ∞ capacitor behaves as open circuit.

Discussion

307.	The average value of the waveform is
Answer»

Discussion

308.	In a series RLC circuit p.f is lagging when < resonance frequency.
Answer» When f < fr, XC > XL and p.f is leading.

Discussion

309.	Thevenin's impedance of an ac network is in general
Answer» Thevenin's impedance may be inductive or capacitive.

Discussion

310.	If operator '' = 1 ∠120° then (1 - ) =
Answer» 1 - a = 1 - 1∠120° = 1 + 0.5 - j 0.866 = 1.5 - j 0.866 = 3∠-30°.

Discussion

311.	A system is at rest for < 0. It is given by If steady state is reached at = 0, then the value of angle A is given by
Answer» = U(t) sin (2t + A) y(s).s + 2y(s) = char.eqn S + 2 = 0 jω + 2 = 0 j2 + 2 = 0 1 + j = 0 tan-1(1) 45°.

Discussion

312.	An RLC series circuit has Q = 100 and ω = 20 rad/sec. The bandwidth is
Answer»

Discussion

313.	For making a capacitor, the dielectric should have
Answer» A high ∈r will lead to high value of capacitance.

Discussion

314.	In an unloaded transformer, the fluxes limiting the primary and secondary are 30 mWb and 20 mWb. The coefficient of coupling is
Answer» Φ11 = (1 - k) Φ1 φ11 = φ1 - φ2 30 - 20 10 mWb 10 mWb = (1 - k) 30m 0.33 = 1 - k k = 0.67 .

Discussion

315.	Heat in calories = IR/4.186.
Answer» Calories and joules are related by mechanical equivalent of heat which is 4.186 .

Discussion

316.	Poles and zeros of a driving point function of a network are simple and alternate on ω axis. The network consists of
Answer» In network having only L and C, poles and zeros of driving point function are simple and alternate on jω axis.

Discussion

317.	The distance between the plates of a parallel plate capacitor is . The dielectric is in two parts, each of equal thickness but dielectric constants ∈ and ∈ respectively. The total capacitance will be proportional to
Answer» The combination is equal to two capacitors in series. Hence, .

Discussion

318.	An air cored coil has an inductance of 0.3 H. If another coil has an iron core of μ = 500, the remaining quantities being the same, the inductance of the second coil will be
Answer» Inductance a μr.

Discussion

319.	The units for apparent power are watts.
Answer» Apparent power has units of volt-amperes.

Discussion

320.	In a series RLC circuit the phase angle θ of impedance Z ∠θ is positive. The circuit will behave as
Answer» In RL circuits phase angle of Z is positive.

Discussion

321.	A two branch parallel tuned circuit has a coil of resistance 100 &ohm; and inductance 0.005 H in one branch and 10 F capacitor in the second branch. At resonance frequency is
Answer» = = 44.67 x 104 rad/sec.

Discussion

322.	For the circuit in figure, fed by a unit step voltage, =
Answer» At t = 0, vc = 0 and at t = ∞, vc = 1. This condition is satisfied only by 1 - e-t/RC.

Discussion

323.	For the network of figure, =
Answer»

Discussion

324.	A circuit is replaced by its Thevenin's equivalent to find current through a certain branch. If V = 10 V and R = 20 &ohm;, the current through the branch
Answer» Hence less than 0.5 A.

Discussion

325.	An ideal transformer has a turn ratio of 2 : 1. Taking side as port 1 and side as port 2, transmission parameters of transformer are
Answer» For the given data V1 = 2V2 and I1 = 0.5 I2 .

Discussion

326.	The voltage in the figure
Answer» Apply mesh analysis in both the mesh by converting 8A current source into voltage source. 80 = 18 I1 - 6I2 + 16 1 - 12I2 - 6I2 + 6I1 = - 16 I1 = 4.3A, I2 = 2.3A Hence e0 = 13I2 13 x 2.3 28 volts.

Discussion

327.	In the given circuit, viewed from AB, the circuit can be reduced to an equivalent circuit as
Answer» For RTh, Voltage source will be short circuited RTh = 2.4 &ohm;, VAB = 10 - 6 I 7 V.

Discussion

328.	For the network of figure KVL for first loop is
Answer» M term is negative because i1, is entering the dotted terminal and i2, is leaving the dotted terminal.

Discussion

329.	An RC series circuit is charged by a voltage E. After a long time the battery is removed and a short circuit is placed across R-C. Then
Answer» Direction of current during discharging is opposite to that during charging.

Discussion

330.	If A = 3 + 1, A =
Answer» 3 + j1 = 10∠18.43° = (10)4

Discussion

331.	In a two terminals network the O.C. voltage measured at the given terminals is 100 V and s.c., currents at the same terminals 5 A. If a load of 80 &ohm; resistance is connected at the terminals, load current is
Answer»

Discussion

332.	Figure shows a dc circuit fed by a current source. With respect to terminals AB, Thevenin's voltage and Thevenin's resistance are
Answer»

Discussion

333.	Colour code of carbon resistors has only two bands.
Answer» It has four bands.

Discussion

334.	A coil has resistance R and inductance L. At ω = ∞ the phase angle between voltage and current is
Answer» When ω = ∞, XL = ωL = ∞.

Discussion

335.	Two coils having self inductances of 10 mH and 40 mH are mutually coupled. The maximum possible mutual inductance is
Answer» Maximum mutual inductance = L1L2 = 20 mH.

Discussion

336.	In the circuit shown in figure the current of sinusoidal source is
Answer» Currents in resistance and inductance are out of phase by 90°. Hence I = 122 + 162 = 20 A.

Discussion

337.	In an RL series circuit the inductance is 1H and current at an instant is 0.6 A. The energy stored in magnetic field is
Answer» Energy = 0.5 LI2 = 0.5 x 1 x 0.62 = 0.18 J.

Discussion

338.	In a series ac circuit a voltage of 20 V at 25 Hz causes a current of 0.20 A, while the same voltage at 75 Hz causes a current of 0.12 A. The circuit consists of
Answer» As f increases impedance increases and current decreases in RL circuit.

Discussion

339.	The resistance of a 230 V, 100 W lamp is
Answer»

Discussion

340.	System function , For a signal sin 2, the steady state response is
Answer» .

Discussion

341.	A network has two branches in parallel. One branch contains impedance Z and the other branch has impedance Z. If it is fed from an ac voltage V of frequency f, the current through Z depends, on
Answer» In parallel branches, the current through any branch depends only on voltage, impedance and frequency only.

Discussion

342.	An RLC series circuit has R = 7.07 &ohm;, L = .707 H and C = 7.07 μF. At Half power frequencies the circuit impedance is likely to be
Answer» At half power frequency the circuit impedance is 2 times resistance.

Discussion

343.	In a series R, L, C circuit the impedance triangle is the same when X < X and X > X .
Answer» The quadrants are different.

Discussion

344.	The zinc can of a dry cell serves as positive terminal.
Answer» Zinc can serves as negative terminal.

Discussion

345.	A magnetic circuit has an iron length of 20 cm and air gap length 0.1 cm. If μ = 200 then
Answer»

Discussion

346.	A circuit is fed by two sources of the same frequency and values 100 ∠0° V and 20 ∠30°V. The current in a particular branch is 5 ∠19° A. If the magnitudes of the sources and changed to 200 ∠0° V and 40 ∠30° V, the current in that branch should be
Answer» Since strengths of both sources are doubled, the current would become twice.

Discussion

347.	Two coils X and Y have self inductances of 5 mH and 10 mH and mutual inductance of 3 mH. If the current in coils X change at a steady rate of 100 A/s, the emf induced in coil Y is
Answer»

Discussion

348.	Two capacitors of 2 μF and 4 μF capacitance are connected in series across a 30 V dc battery. After the capacitors have been charged, the voltage across them will be
Answer» Charge will be the same. Since Q = C V voltage will be inversely proportional to Q. Hence 20 V and 10 V.

Discussion

349.	A 50 Hz current has an amplitude of 10 A. The rate of change of current at = 0.005 after = 0 and is increasing is
Answer» i = 10 sin 314.16 t, At t = 0.005, i = 314.16 cos (314.16 x .005) = 0.

Discussion

350.	In the circuit of figure the voltage across C at = 0 is
Answer» Voltage across a capacitor cannot change instantaneously.

Discussion

Explore topic-wise InterviewSolutions in .

Two similar coupled coils are connected in series. The total inductance in series aiding connection is 100 mH. If currents is 3 A, the energy stored in magnetic field is

The Voltage in the figure,

A 1 μF capacitor is connected to 12 V battery. The energy stored in the capacitor is

The poles with greater displacement from the real axis correspond to

In figure, the capacitor is charged to 1 V. At = 0 the switch is closed so that = . When = 0.37 A, the voltage across capacitor is

In the circuit of figure the current through C at = ∞ is

The average value of the waveform is

In a series RLC circuit p.f is lagging when < resonance frequency.

Thevenin's impedance of an ac network is in general

If operator '' = 1 ∠120° then (1 - ) =

A system is at rest for < 0. It is given by If steady state is reached at = 0, then the value of angle A is given by

An RLC series circuit has Q = 100 and ω = 20 rad/sec. The bandwidth is

For making a capacitor, the dielectric should have

In an unloaded transformer, the fluxes limiting the primary and secondary are 30 mWb and 20 mWb. The coefficient of coupling is

Heat in calories = IR/4.186.

Poles and zeros of a driving point function of a network are simple and alternate on ω axis. The network consists of

The distance between the plates of a parallel plate capacitor is . The dielectric is in two parts, each of equal thickness but dielectric constants ∈ and ∈ respectively. The total capacitance will be proportional to

An air cored coil has an inductance of 0.3 H. If another coil has an iron core of μ = 500, the remaining quantities being the same, the inductance of the second coil will be

The units for apparent power are watts.

In a series RLC circuit the phase angle θ of impedance Z ∠θ is positive. The circuit will behave as

A two branch parallel tuned circuit has a coil of resistance 100 &ohm; and inductance 0.005 H in one branch and 10 F capacitor in the second branch. At resonance frequency is

For the circuit in figure, fed by a unit step voltage, =

For the network of figure, =

A circuit is replaced by its Thevenin's equivalent to find current through a certain branch. If V = 10 V and R = 20 &ohm;, the current through the branch

An ideal transformer has a turn ratio of 2 : 1. Taking side as port 1 and side as port 2, transmission parameters of transformer are

The voltage in the figure

In the given circuit, viewed from AB, the circuit can be reduced to an equivalent circuit as

For the network of figure KVL for first loop is

An RC series circuit is charged by a voltage E. After a long time the battery is removed and a short circuit is placed across R-C. Then

If A = 3 + 1, A =

In a two terminals network the O.C. voltage measured at the given terminals is 100 V and s.c., currents at the same terminals 5 A. If a load of 80 &ohm; resistance is connected at the terminals, load current is

Figure shows a dc circuit fed by a current source. With respect to terminals AB, Thevenin's voltage and Thevenin's resistance are

Colour code of carbon resistors has only two bands.

A coil has resistance R and inductance L. At ω = ∞ the phase angle between voltage and current is

Two coils having self inductances of 10 mH and 40 mH are mutually coupled. The maximum possible mutual inductance is

In the circuit shown in figure the current of sinusoidal source is

In an RL series circuit the inductance is 1H and current at an instant is 0.6 A. The energy stored in magnetic field is

In a series ac circuit a voltage of 20 V at 25 Hz causes a current of 0.20 A, while the same voltage at 75 Hz causes a current of 0.12 A. The circuit consists of

The resistance of a 230 V, 100 W lamp is

System function , For a signal sin 2, the steady state response is

A network has two branches in parallel. One branch contains impedance Z and the other branch has impedance Z. If it is fed from an ac voltage V of frequency f, the current through Z depends, on

An RLC series circuit has R = 7.07 &ohm;, L = .707 H and C = 7.07 μF. At Half power frequencies the circuit impedance is likely to be

In a series R, L, C circuit the impedance triangle is the same when X < X and X > X .

The zinc can of a dry cell serves as positive terminal.

A magnetic circuit has an iron length of 20 cm and air gap length 0.1 cm. If μ = 200 then

A circuit is fed by two sources of the same frequency and values 100 ∠0° V and 20 ∠30°V. The current in a particular branch is 5 ∠19° A. If the magnitudes of the sources and changed to 200 ∠0° V and 40 ∠30° V, the current in that branch should be

Two coils X and Y have self inductances of 5 mH and 10 mH and mutual inductance of 3 mH. If the current in coils X change at a steady rate of 100 A/s, the emf induced in coil Y is

Two capacitors of 2 μF and 4 μF capacitance are connected in series across a 30 V dc battery. After the capacitors have been charged, the voltage across them will be

A 50 Hz current has an amplitude of 10 A. The rate of change of current at = 0.005 after = 0 and is increasing is

In the circuit of figure the voltage across C at = 0 is