Maximum Average Power

Ask

An independent voltage source in series with an impedance Z_s=R+jX delivers a maximum average power to a load impedance Z_L when

(a)Z_L = R + jX

(b)Z_L = R

(c)Z_L=jX

(d)Z_L = R - jX

Answer is ( )

Concept

Type Reasoning here

Driving point impedance

Ask

The first & last critical frequencies (singularities) of a driving point impedance function of a passive network having two kinds of elements are a pole and a zero respectively.
The above property will be satisfied by
(a)R L network only
(b)RC network only
(c)LC network only
(d)RC & R L networks




Answer is ( )

Concept

Type Reasoning here

Current Flow through Non - Uniform Area

Ask

A current is flowing through a conductor with non-uniform area of cross-section. Then
(a) current will be different at different cross-sections.
(b) current will be the same at all the cross-sections.
(c) current will be different but current density will be same at all the cross-sections
(d) current will be the same but current density will be different at different cross-sections


Answer is ( )

Concept

Type Reasoning here

Capacitor Related 1.1

Ask

In the circuit of figure the voltage across capacitor when switch is closed at t = ∞ is

(a) 0 V

(b) 20 V

(c) very large

(d) 7.5 V

Answer is ( )

Concept

Type Reasoning here

Thevenin's Vge

Ask

For the circuit shown in figure , Thevenin's voltage & Thevenin's equivalent resistance at terminal a- b is:

(a) 5 V & 2 Ohm

(b)7.5 V & 2.5 Ohm

(c)4 V & 2 Ohm

(d)3V & 2.5 Ohm

Answer is ( )

Concept

Type Reasoning here

Maximum Load Transfer

Ask

A source of angular frequency 1 rad/ s has a source impedance consisting  of  1 ohm  resistance in series with 1H inductance.The load that will obtain the maximum transfer is

(a)1 Ohm

(b) 1 Ohm Resistance in Parallel with 1 H inductance

(c) 1 Ohm Resistance in series with 1 F Capacitor

(d) 1 Ohm Resistance in Parallel with 1 F Capacitor

Answer is ( )

Concept

Type Reasoning here

Capacitor Related

Ask

A 0.5 μF capacitor is connected across a 10 V battery. After a long time, the circuit current and voltage across capacitor will be
(a) 0.5 A and 0 V
(b) 0 A and 10 V
(c) 20 A and 5 V
(d) 0.05 A and 5 V



Answer is ( )

Concept

Type Reasoning here

R-C series circuit

Ask

In an R-C series circuit excited by a voltage E, the charge across capacitor at t = 0+ is
(a) 0
(b) CE
(c) CE (1 - e-t/RC)
(d) none of the above



Answer is ( a )

Concept

Type Reasoning here

RMS Values

Ask

Wave A = 100 sin ωt and wave B = 100 cos ωt. Then
(a) rms values of the two waves are equal
(b) rms values of A is more than that of B
(c) rms values of A is less than that of B
(d) rms values of the two waves may or may not be equal



Answer is ( )

Concept

Type Reasoning here

RMS and Average Values

Ask

 The terms RMS and average values apply to
(a) sine waves only
(b) square waves only
(c) sine and square waves only
(d) all wave shapes


Answer is ( )

Concept

Type Reasoning here

Stat- Delta Problems

Ask

A 3-phase star connected symmetrical load consumes P watts of power from a balanced supply. If the same load is connected in delta to the same supply,the power consumption will be

(a) P

(b) $\sqrt{3P}$

(c) 3P

(d) none of above

Answer is ( c )

Concept

Resistors

Ask

A network contains only independent current sources and resistors. If the values of all resistors are doubled,the values of the node voltages

(a) will become half

(b) will remain unchanged

(c) will become double

(d) cannot be determined

Answer is ( c )

Concept

Type Reasoning here

Parallel Inductors

Ask

If three 9mH inductors are connected in parallel without mutual inductance then the total inductance will be

(a) 3 mH

(b) 9 mH

(c) 27 mH

(d) 18 mH

Answer is ( a )

Concept

Type Reasoning here

Resonance

Ask

 Current is __ times the maximum current at half power points of resonance

(a) 0.707

(b) 1.414

(c) 0.5

(d) 0.632

Answer is ( a )

Concept

Type Reasoning here

Wheat Stone Bridge

Ask

In the circuit shown in figure,current in 2Ω resistor is 
(a) zero

(b) -2A

(c) 2A

(d) 1A

Answer is ( c )

Concept

Type Reasoning here

Resistance

Ask

Property of an electric circuit that dissipates electric energy is

(a) Reactance

(b) Impedance

(c) Resistance

(d) Conductance

Answer is ( c )

Concept

Type Reasoning here

Series RLC circuit 1.1

Ask

In series RLC circuit

(a) Current lags $V_{L}$ by 90°

(b) Current leads $V_{L}$ by 90°

(c) $X_{L}$ leads $X_{C}$ by 90°

(d) $Z = j*X_{L}$ at resonance

Answer is ( a )

Concept

Type Reasoning here

Current Source

Ask

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

(a) 28 A   

(b) 4 A

(c) 20 A

(d)insufficient data

Answer is (c)

Concept

$\overrightarrow I = \overrightarrow I_{R} + \overrightarrow I_{L}$
$\lvert I \rvert = \sqrt{ 144 + 256}$ = 20 A

Average Power - Passive Elements

Ask

A 10mH inductor carries a sinusoidal current of 1A rms at a frequency of 50Hz.The average power dissipated by the inductor is

(a) 0 W

(b) 0.25 W

(c) 0.5 W

(d) 1 W

Answer is ( a )

Concept

Explanation:The average power dissipated by a circuit which has only reactive element(purely capacitive or purely inductive) is 0.

Active Power

Ask

An AC Source of 200V rms supplies an active power of 600W and reactive power of 800VAR. The rms current drawn from the source is

(a) 10A

(b) 5A

(c) 3.75A

(d) 2.5A

Answer is ( b )

Concept

Explanation: $V_{s} = 200V (rms)$

$P = 600W , Q = 800VAR$

$P = V_{s}I_{s}cos\phi = 600$

$\therefore I_{s}cos\phi = 600/200 = 3 $...Eqn(1)

$Q = V_{s}I_{s}sin\phi = 800$

$\therefore I_{s}sin\phi = 800/200 = 4 $...Eqn(2)

$\therefore$ From Eqn(1) and (2) $I_{s}^{2}(sin^{2}\phi + cos^{2}\phi)$ = 9 +16 = 25