577 + Interview Questions in Networks Analysis and Synthesis in Electronics and Communication Engineering Page 9 InterviewSolution

401.	If A = 16 ∠64°, (A) is
Answer»

Discussion

402.	In figure the total inductance of the circuit is
Answer» Inductances are in series aiding connection. M terms will become twice because of mutual inductance between L1 and L2 and that between L2 and L1.

Discussion

403.	For a high pass filter attenuation = 0 at = 0.
Answer» Attenuation is infinite at f = 0 for high pass filter.

Discussion

404.	In the network of figure, the voltage drops across R, R, R are 6 V, 8 V and 12 V with polarities as shown. The value of R is
Answer» From the given data the current through R1 is 4 A.

Discussion

405.	Double integration of unit step function leads to
Answer» Integral of unit step function is ramp and integral of ramp is doublet.

Discussion

406.	A conductor has a cylindrical shape with a diameter . Its resistance is 2 &ohm;. It is recast into a cylindrical conductor of diameter 0.3. The resistance of new conductor is likely to be
Answer» Since new diameter is 0.3 d, the new area of cross-section a (0.3 d)2. The volume remains the same. Therefore length increase by a factor . Hence .

Discussion

407.	For an RLC series circuit, Z() will be of the form of
Answer» which is similar to

Discussion

408.	In the circuit shown in the figure, steady-state was reached when the switch S was open. The switch was closed at = 0. The initial value of the current through the capacitor 2 C is
Answer» At steady state capacitor will be open and inductor will short circuited. V across 2C will be = 12v .

Discussion

409.	As temperature increases, the temperature coefficient of a metal
Answer» It at is temperature coefficient at t°C and a0 is temperature coefficient at 0°C. .

Discussion

410.	A wire has a resistance R ohm. If another wire of the same material and same weight has double the diameter (as compared to the first wire), the resistance of the second wire will be
Answer» Since diameter is double, area of cross-section is four times and length is one-fourth. .

Discussion

411.	In the circuit of figure the current through 5 &ohm; resistance at = 0 is
Answer» Since 3 ohm resistance is short-circuited by capacitor, I = 20/5 A.

Discussion

412.	In active filters inductances are divided because they
Answer» Active filters consist of electronic components and have very small size.

Discussion

413.	Three resistance of 15 &ohm; each are connected in delta. The resistance of equivalent star will have a value of
Answer»

Discussion

414.	The circuit in figure(1) is replaced by that in figure(2). It remains same R will be
Answer» Net resistance of circuit is 4.571 R and that of circuit is 0.571 R. Hence R0 be 4R.

Discussion

415.	In a varistor the - graph is linear.
Answer» The v-i graph, in varistor, is non-linear.

Discussion

416.	The resistance R in the circuit is
Answer» (6 + 6/5) \|\| (18 + 18/5) = 5.4 5.4 + 3.6 9 &ohm;.

Discussion

417.	In the circuit of figure the current through L at = ∞ is
Answer» At t = ∞ inductance behaves as short-circuit.

Discussion

418.	In using KCL it is necessary that current leaving a node is written as negative.
Answer» It may be written as positive or negative as per convenience.

Discussion

419.	A resistor is rated at 0.75 watt, 1 k&ohm;. Its current rating is
Answer» 0.75 = I2 x 1 x 1000 or I = 27.386 mA.

Discussion

420.	A series R-L circuit has R = 1 &ohm; and L = 1 H. It is excited by a V battery at = 0. The steady state condition is reached at
Answer» i = 10 (1 - e-t). It reaches steadily state value at t = ∞

Discussion

421.	The current source in figure, can be replaced by
Answer» The parallel combination of 20 &ohm; and 5 &ohm; is 4 &ohm;. Therefore, strength of current source is 4 x 4 = 16 A and source resistance is 4 ohms.

Discussion

422.	A parallel plate capacitor with air as dielectric has a capacitance C. If the dielectric has a dielectric constant ∈ and the remaining dimensions are the same, the capacitance will be
Answer» Capacitance ∝ ∈r.

Discussion

423.	A bulb rated at 60 W, 120 V is used for 30 minutes. The charge associated with this operation is
Answer»

Discussion

424.	In the circuit shown in the figure, the current supplied by the sinusoidal current source I is
Answer» I = (12)2 + (16)2 = 20 A.

Discussion

425.	The frame of an electric motor is earthed through three earthing plates resistances 30 &ohm;, 20 &ohm; and 10 &ohm; respectively. During fault the energy dissipated by three plates are W, W and W. Then
Answer» Energy dissipated by the plate with lowest resistance is maximum.

Discussion

426.	If figure, power dissipated in 30&ohm; resistance will be maximum when value of R =
Answer» When R = 0, circuit current = and power dissipated = watts, which is the maximum possible value.

Discussion

427.	Two voltages are 50 ∠0 V and 75 ∠ - 60° V. The sum of these voltages is
Answer» 50Ð0 = 50 + j 0.75∠-60° = 37.5 - j 64.95 Sum = (50 + 37.5) - j 64.95 = 87.5 - j 64.95 = 109∠-36.6°

Discussion

428.	Two coil have their axis perpendicular to each other. The coefficient of coupling is
Answer» When axis are perpendicular then there is no mutual coupling.

Discussion

429.	In a series RLC circuit, p-f is leading if X < X.
Answer» If XC < XL power factor is lagging.

Discussion

430.	If the voltage across the last resistor is V, and all the resistor is unity. Then V is given by
Answer» Let the last voltage is V1 = V, V2 = Voltage across both 1 &ohm; resistor V + V = 2V Current in shunt resistor = i ia = ib + ic 2v + v 3v V3 = ib x R + ia x R 3v + 2v = 5v V4 = 5v + 8v = 13v.

Discussion

431.	In figure, at = 0 is
Answer» Inductance behaves as O.C. at t = 0+.

Discussion

432.	In a purely inductive circuit, the current __________ the voltage by __________ .
Answer» In inductive circuit current lags the voltage by 90°.

Discussion

433.	One commercial unit of energy is equal to
Answer» Consumers are charged on the basis of kWh of energy used.

Discussion

434.	In figure which is correct at any time
Answer» As per KCL sum of currents entering a node is equal to sum of currents leaving the node.

Discussion

435.	Two coupled coils with self inductances of 4 mH and 16 mH are connected in series. The maximum possible value of inductance can be
Answer» Inductance = 4 + 16 + 24 x 16 = 36 mH.

Discussion

436.	Elements R, L, C are connected in parallel and excited by a dc current I. If , and are the currents through R, L, C respectively then at = 0
Answer» Capacitor behaves as a short-circuit at t = 0.

Discussion

437.	In a practical voltage source, the terminal voltage
Answer» A practical voltage source has some source resistance. Because of voltage drop across source resistance, terminal voltage cannot be higher than source voltage. If current is zero, terminal voltage and source voltage are equal.

Discussion

438.	When slider of the potentiometer AB is in the position shown in figure, what resistance reading would be indicated by an ohmmeter connected between A and C?
Answer» A to C will act as short circuit, hence R = 0 if it open then R = ∞.

Discussion

439.	The three sides of an admittance triangle denote
Answer» Admittance triangle depicts admittance Y and its components G and B.

Discussion

440.	A step voltage E is applied to an R-L series circuit. At = 0, the current in the circuit is
Answer» Inductance does not allow the current to increase instantaneously.

Discussion

441.	In figure, the magnitude of V
Answer» V depends on magnitudes and phase angles of Va and Vb.

Discussion

442.	To find current in a resistance connected in a network, Thevenin's theorem is used V = 20 V and R = 5 &ohm;. The current through the resistance
Answer»

Discussion

443.	A step voltage E is applied to a series R-L circuit. The rate of change of current is maximum at =
Answer»

Discussion

444.	The energy stored in a coil is 108 J. It is opened suddenly in 10 ms. The power dissipated instantaneously across the blades of switch is
Answer»

Discussion

445.	Thermistor has a positive temperature coefficient.
Answer» Temperature coefficient of thermistor is negative.

Discussion

446.	The switch in figure is initially closed. At = 0 the switch is opened. At = 0, the current through R is
Answer» At t = 0+ capacitor behaves as short-circuit.

Discussion

447.	A network has 10 nodes and 17 branches. The number of different node pair are
Answer» One node is reference node. Therefore the system has 9 node pairs.

Discussion

448.	In a series RC circuit Z = (R + ωC).
Answer»

Discussion

449.	If V = 20 + j20, then log(A) A is
Answer» 20 x j 20 = 28.28 Ð45° loge V = loge (28.28) + = 3.342 j.785.

Discussion

450.	In an ac network the sum of currents entering a node is 10 ∠45°. The sum of currents leaving the node is
Answer» As per KCL sum of currents entering a node is equal to sum of currents leaving a node.

Discussion

Explore topic-wise InterviewSolutions in .

If A = 16 ∠64°, (A) is

In figure the total inductance of the circuit is

For a high pass filter attenuation = 0 at = 0.

In the network of figure, the voltage drops across R, R, R are 6 V, 8 V and 12 V with polarities as shown. The value of R is

Double integration of unit step function leads to

A conductor has a cylindrical shape with a diameter . Its resistance is 2 &ohm;. It is recast into a cylindrical conductor of diameter 0.3. The resistance of new conductor is likely to be

For an RLC series circuit, Z() will be of the form of

In the circuit shown in the figure, steady-state was reached when the switch S was open. The switch was closed at = 0. The initial value of the current through the capacitor 2 C is

As temperature increases, the temperature coefficient of a metal

A wire has a resistance R ohm. If another wire of the same material and same weight has double the diameter (as compared to the first wire), the resistance of the second wire will be

In the circuit of figure the current through 5 &ohm; resistance at = 0 is

In active filters inductances are divided because they

Three resistance of 15 &ohm; each are connected in delta. The resistance of equivalent star will have a value of

The circuit in figure(1) is replaced by that in figure(2). It remains same R will be

In a varistor the - graph is linear.

The resistance R in the circuit is

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

In using KCL it is necessary that current leaving a node is written as negative.

A resistor is rated at 0.75 watt, 1 k&ohm;. Its current rating is

A series R-L circuit has R = 1 &ohm; and L = 1 H. It is excited by a V battery at = 0. The steady state condition is reached at

The current source in figure, can be replaced by

A parallel plate capacitor with air as dielectric has a capacitance C. If the dielectric has a dielectric constant ∈ and the remaining dimensions are the same, the capacitance will be

A bulb rated at 60 W, 120 V is used for 30 minutes. The charge associated with this operation is

In the circuit shown in the figure, the current supplied by the sinusoidal current source I is

The frame of an electric motor is earthed through three earthing plates resistances 30 &ohm;, 20 &ohm; and 10 &ohm; respectively. During fault the energy dissipated by three plates are W, W and W. Then

If figure, power dissipated in 30&ohm; resistance will be maximum when value of R =

Two voltages are 50 ∠0 V and 75 ∠ - 60° V. The sum of these voltages is

Two coil have their axis perpendicular to each other. The coefficient of coupling is

In a series RLC circuit, p-f is leading if X < X.

If the voltage across the last resistor is V, and all the resistor is unity. Then V is given by

In figure, at = 0 is

In a purely inductive circuit, the current __________ the voltage by __________ .

One commercial unit of energy is equal to

In figure which is correct at any time

Two coupled coils with self inductances of 4 mH and 16 mH are connected in series. The maximum possible value of inductance can be

Elements R, L, C are connected in parallel and excited by a dc current I. If , and are the currents through R, L, C respectively then at = 0

In a practical voltage source, the terminal voltage

When slider of the potentiometer AB is in the position shown in figure, what resistance reading would be indicated by an ohmmeter connected between A and C?

The three sides of an admittance triangle denote

A step voltage E is applied to an R-L series circuit. At = 0, the current in the circuit is

In figure, the magnitude of V

To find current in a resistance connected in a network, Thevenin's theorem is used V = 20 V and R = 5 &ohm;. The current through the resistance

A step voltage E is applied to a series R-L circuit. The rate of change of current is maximum at =

The energy stored in a coil is 108 J. It is opened suddenly in 10 ms. The power dissipated instantaneously across the blades of switch is

Thermistor has a positive temperature coefficient.

The switch in figure is initially closed. At = 0 the switch is opened. At = 0, the current through R is

A network has 10 nodes and 17 branches. The number of different node pair are

In a series RC circuit Z = (R + ωC).

If V = 20 + j20, then log(A) A is

In an ac network the sum of currents entering a node is 10 ∠45°. The sum of currents leaving the node is

In a purely inductive circuit, the current the voltage by .