EE OBJECTIVES

For open circuited condition of Thevenin's theorem, all sources of emf in the network are replaced by A. their internal impedance B. their internal resistance C. as a total a big source of emf D. their internal reactance

A

Another reason for improving the power factor is A. to avoid poor voltage regulation B. to keep voltage regulation constant C. to increase the voltage regulation D. to decrease the voltage regulation

A

At a frequency lass than the resonant frequency A. series circuit is capacitive and parallel circuit is inductive B. series circuit is inductive and parallel circuit is capacitive C. both circuits are inductive D. both circuits are capacitive

A

For an RL circuit, the power factor cannot be less than _________ or greater than _________. A. 0, 1 B. 1, 0 C. 0, -1 D. -1, 0

A

For the same load, if the power factor of load is reduced, it will A. draw more current B. less current C. same current but less power D. less current but more power

A

For the same original network end load, Thevenin's and Norton's equivalent circuits are related by A. Eth = InZth = InZn B. Eth = IthZn = IthZth C. Zn = Eth /Ith D. Zth = En /In

A

In RLC circuits, the current at resonance is A. maximum in series circuit and minimum in parallel circuit B. maximum in parallel circuit and minimum in series circuit C. maximum in both the circuits D. minimum in both the circuits

A

The net reactance in a n RLC circuit is A. XL B. XC C. XC - XL D. X L - X C

D

The formula for the resonant frequency is f = A. √LC B. 1/ √LC C. 2π√LC D. 1/2π√LC

D

In a balanced three phase star connected system the line voltage is A. the phasor difference of the two phase voltages B. the phasor sum of the two phase voltages C. 0.707 times the phase voltage D. 1.414 times the phase voltage

A

In a series RL circuit, the inductor current _____ the resistor current A. lags B. leads C. is equal D. is negative

A

In a series circuit consisting of resistance and reactance, power factor is defined as the ratio of A. resistance to impedance B. resistance to reactance C. reactance to impedance D. reactance to resistance

A

In an a.c. circuit, a low value of reactive volt ampere compared with watts indicates A. high power factor B. unity power factor C.leading power factor D. low power factor

A

In compensation theorem a network containing generator can be replaced by A. its zero internal impedance B. its infinite impedance C. another generator D. L.C. circuit

A

In the impedance triangle, the inductive reactance and impedance phasor are analogous to the ________ and ________ phasor respectively in the voltage triangle. A. inductive voltage, total voltage B. inductive current, total current C. inductive voltage, resistive voltage D. inductive current, resistive current

A

It is not easy to find the value of impedance for a parallel circuit but power factor can easily be obtained as a ratio of A. active current to line current B. reactive current to line current C. line current to active current D. line current to reactive current

A

Many industrial tariffs penalize consumers whose power factor falls A. below 0.8 B. below unity C. between 0.8 to 0.95 D. between 0.95 to unity

A

Open circuit voltage is the potential difference between two points when the impedance between these points is A. infinity B. reactive C. zero D. capacitive

A

Power factor improvement may be achieved by the use of A. synchronous motor B. induction motor C. long transmission line D. short transmission line

A

Power in a three phase delta system with balanced load is equal to A. 3 × VL × IL × power factor B. 3 × Vph × Iph × power factor C. 3 × Vph × IL × power factor D. 3 × VL × IL × power factor

A

Power in star connected system is A. equal to that of delta system B. √2 times that of delta system C. √3 times that of delta system D. 3 times that of delta system

A

Regarding Norton's equivalent, which of the following is not correct? A. Norton's equivalent is the voltage equivalent of the network. B. Norton's equivalent is the current equivalent of the network. C. Norton's equivalent resistance is the same as the Thevenin equivalent resistance. D. The load is connected in parallel to the Norton equivalent resistance and Norton's equivalent source.

A

The current in RLC series circuit, i.e. at resonance is A. maximum B. minimum C. infinity D. zero

A

The phase angle for a series RC circuit may be computed as the angle between the ______ and _______ phasors A. resistance, impedance B. resistance, reactance C. resistance, capacitance D. impedance, reactance

A

The relationship between voltage and current is same for two opposite directions of current in case of A. bilateral network B. active network C. unilateral network D. passive network

A

The superposition theorem is applicable to A. linear responses only B. linear and non-linear responses only C. linear, non-linear and time variant response D. non-linear responses only

A

Two wattmeters can be used to measure 3-phase power for a A. balanced and unbalanced load B. unbalanced load only C. balanced load only D. unity power factor only

A

What is the minimum number of wattmeters required to measure unbalanced power for a three phase system? A. two B. four C. three D. one

A

Which of the following is an active element of a circuit? A. ideal current source B. resistance C. inductance D. capacitance

A

Which of the following statement is not correct? A. Ideal voltage source is one whose internal conductance is zero. B. Ideal current source is one whose internal conductance is zero. C. Ideal voltage source is one whose internal resistance is zero. D. Ideal voltage source is one whose generated voltage is equal to the available terminal voltage.

A

A series resonant circuit is capacitive at f = 100 Hz. The circuit will be inductive somewhere at A. f < 100 Hz B. f > 100 Hz C. f = 100 Hz by increasing the value of the resistance D. f = 0

B

A source V has an internal impedance Zin = (R + jX) when it is connected ZL = R - jX the power transferred is A. V2 /4R2 B. V2/4R C. V2/R D. V2/2R

B

An ideal voltage source is that which A. has terminal voltage in proportion to current B. has zero internal resistance C. has terminal voltage in proportion to load D. has terminal voltage in proportion to power

B

For a series RLC circuit at resonance the current amplitude is ______ and for a fixed voltage amplitude and the power factor is _________ A. minimum, zero B. minimum, unity C. maximum, zero D. maximum, unity

B

For an unbalanced load which connection is suitable A. 3 wire open delta B. 4 wire star connection C. 3 wire delta connection D. 3 wire star connection

B

For maximum power transfer, according to maximum power transfer theorem, source impedance A. must be very much large as compared to the load impedance B. must be complex conjugate of load impedance C. must be equal to load impedance D. must be very small as compared to the load impedance

B

In a pure reactive circuit, the power factor is A. lagging B. zero C. leading D. unity

B

In a series RL circuit phasor diagram, total voltage may be presented by the ________ phasor and the resistor voltage may be represented by the ________ phasor. A. current, voltage B. current resistance, current C. impedance, resistance D. impedance, inductance

B

In an RLC circuit, the impedance at resonance is A. maximum, B. minimum C. infinity D. zero

B

In case of delta connected circuit, when one resistor is open, power will be A. unaltered B. reduced by 1/3 C. reduced to 1/9 D. reduced to 1/16

B

In resonant circuits, the power factor at resonance is A. zero B. 1 C. 0.5 D. 0.707

B

In two wattmeter method, the reading of one of the wattmeter will be zero when A. power factor is unity B. power factor is 0.5 C. load in one of the phases is zero D. a neutral wire is not provided

B

In two wattmeter method, the readings of the wattmeter will be identical when A. load in one of the phases is zero B. power factor is unity C. power factor is 0.5 D. neutral is earthed

B

One of the reasons for improving the power factor is A. to increase the reactive power B. to decrease the reactive power C. to increase the real power D. none of these

B

Power factor is defines as the ratio of A. volt amperes to watts B. watts to volt amperes C. volt amperes reactive to watts D. watts to volt amperes reactive

B

Power factor of an inductive circuit can be improved by connecting a capacitor to it in A. series B. parallel C. either series or parallel D. depends on the value of the capacitor

B

Reciprocity theorem is valid for A. active network only B. passive network only C. active and passive network both D. none of the above

B

The advantage of using static capacitor to improve the power factor is because they A. are not variable B. are almost loss free C. provide continuous change of power factor D. all of the above

B

The advantages of star connections over delta connections for some phase voltage is that it gives A. step down current B. extra step up voltage C. extra step up current D. extra step up power

B

The current in any branch of a network in case of Thevenin's theorem is the same as if it were connected to a generator of A. different rating B. emf E1 and internal impedance Z1 C. low rating D. emf E1 and internal impedance zero

B

The most important feature of superposition theorem application is A. that the process is eased very much B. to find d.c. level in e network that has both sources C. that number of equations needed to be solved is reduced very much D. none of the above

B

The phase angle for a series RC circuit is defined as the angle between the ______ and the ________ phasors A. current, resistance voltage B. current, total voltage C. resistance voltage, capacitor voltage D. R, XC

B

The phase angle of a series RL circuit is the angle between the ________ phasor and the ________ phasor. A. resistance, inductive reactance B. resistance, impedance C. inductive reactance, impedance D. inductance, impedance

B

The resistance phasor for a series RC circuit points out to the right. The capacitive reactance phasor points _________ while the diagonal of the rectangle having there two phasors as sides represents the____________. A. up, impedance B. down, impedance C. left, current D. up, total voltage

B

The total voltage in a series RL circuit ______ the current by an angle _____. A. lags, of 90o B. lags, between 0o and 90o C. leads, between 0o and 90o D. leads, between 90o and 180o

B

The voltage across a capacitor _________ the current thought it by ________. A. lags, 45o B. lags, 90o C. leads, 0o D. leads, 90o

B

Which of the following statement is not correct? A. voltage source is an active element B. current source is a passive element C. resistance is a passive element D. conductance is a passive element

B

. A(n) _______ stores and returns energy to a circuit while a(n) _________ dissipates energy. A. resistor, impedance B. resistor, inductor C. inductor, resistor D. inductor, reactance

C

. In a given circuit when power factor is unity the reactive power is A. a maximum B. equal to I2R C. zero D. a minimum

C

. The superposition theorem requires as many circuits to be solved as there are A. meshes B. nodes C. sources D. all of the above

C

A network is said to be non linear if it does not satisfy A. homogeneity condition B. superposition condition C. both A and B D. associative condition

C

A passive network has A. no source of emf B. no source of current C. neither source of current nor source of emf D. none of these

C

If an electrical network having one or more than one voltage source, is transformed into equivalent electrical network with a single voltage source (which is short circuit current of previous circuit) with parallel internal resistance of the network with all current source replaced by their internal resistance. The above illustration is called A. Thevenin's theorem B. Reciprocity theorem C. Norton's theorem D. Superposition theorem

C

If the resistance in a series RC circuit is increased the magnitude of the phase angle A. increases B. remains the same C. decreases D. changes in an indeterminate manner

C

In a balanced three phase star connected circuit the line voltages are equal A. to the line current B. to the phase voltage C. and so are the line currents D. but the line currents are unequal ​

C

In a series RC circuit, the current _______ the total voltage by an angle _______. A. lags, of 45o B. lags, of 0o C. leads, between 0o and 90o D. leads, of 90o

C

In a star connected system line current is A. 0.707 times the phase voltage B. 1.735 times the phase voltage C. equal to the phase current D. 1.414 times the phase voltage

C

In order to find Z in Thevenin's theorem A. all independent voltage and current sources are short circuited B. all independent voltage sources are short circuited and independent current sources are open circuited C. all independent current sources are short circuited and independent voltage sources are open circuited D. all independent voltage sources are open circuited and independent current sources are open circuited

C

Kirchhoff's law is applicable to A. AC circuits only B. passive networks only C. AC as well as DC circuits D. DC circuits only

C

Norton's theorem reduces a two terminal network to A. a constant voltage source and an impedance in parallel B. a constant voltage source and an impedance in series C. a constant current source and an impedance in parallel D. a constant current source and an impedance in series

C

Poor power factor results in all of the following except A. overloading of transformers B. overloading of alternators C. reduction in power losses D. reduction in load handling capacity of electrical system

C

Power factor of magnetizing component of a transformer is A. unity B. 0.8 leading C. always leading D. zero

C

The capacitor of power factor correction are rated in terms of A. voltage B. VA C. kW D. kVAR

D

Regarding Thevenin's equivalent, which of the following is not correct? A. The voltage source in the Thevenin equivalent circuit is the open circuit voltage of the network when load is disconnected. B. The Thevenin equivalent resistance (impedance) is the resistance (impedance) of the network when all voltage sources are short circuited. C. Thevenin equivalent resistance is calculated when all voltage sources are open circuited. D. Thevenin equivalent is the voltage equivalent of the network.

C

The impedance triangle is similar to the _______ triangle with the resistance phasor in place of the ________. A. current, resistor current B. current, resistor voltage C. voltage, impedance D. voltage, resistor voltage

C

The phase displacement between phasors in polyphase system is always A. 90 degrees B. 30 degrees C. 120 degrees D. 360 degrees divided by the number of phases

C

The power factor of a.c. circuit containing both a resistor and a conductor is A. more than unity B. leading by 90 degrees C. between 0 - 1 leading D. between 0 - 1 lagging

C

The power factor of incandescent bulb is A. 0.8 lagging B. 0.8 leading C. unity D. zero

C

The power is to be measured for a balanced delta connected load whose terminals cannot be opened. How many wattmeters do you need? A. four B. one C. two D. three

C

The type of a.c. distribution system commonly used to supply both light and power is the A. open delta system B. three phase delta system C. three phase star system with neutral wire D. three phase star system without neutral wire

C

There will ________ be a frequency, called the _________ frequency at which ___________. A. sometimes, natural; XL = XC B. always, natural; R = 0 C. always, resonant; X L = X C D. sometimes, resonant; R = 0

C

Thevenin's theorem is applicable to network of A. ac circuit only B. dc circuit only C. ac and dc circuit both D. none of the above

C

What is the minimum number of wattmeters required for measuring power of a three phase balanced load? A. two B. four C. one D. three

C

Which of the following is not a non-linear element? A. diode B. transistor C. heater coil D. electric arc with unlike electrodes

C

Which of the following statements is true for a series RLC circuit tuned at resonant frequency? A. the voltage across C > applied voltage B. the voltage across L > applied voltage C. the voltage across L and C > the applied voltage D. the voltage across both L and C < the applied voltage

C

A current of 10 amperes at a power factor of 0.8 lagging is taken from 250 V a.c. supply. The reactive power of the system is A. 2000 watts B. 2000 VA C. 1500 watts D. 1500 Var

D

A factory takes a load of 1000 KW and has a reactive power of 1000 KVA. Its power factor is A. 0.6 B. unity C. 0.8 D. 0.7

D

For a parallel circuit consisting of resistance and reactance, the value of power factor is the ratio of A. impedance to reactance B. reactance to impedance C. resistance to impedance D. impedance to resistance

D

For a three phase unbalanced load A. the power factor of each phase will be in proportional to the load B. the power factor of each phase will be the same C. the power factor of at least one of the phase must be leading D. the power factor of each phase may be different

D

For reciprocity theorem to be applicable to a network in which A. generators are present B. capacitor is present C. inductor is present D. generators are not present

D

In a delta connected system the line current is A. 1.414 times the phase current B. phasor sum of the two phase currents C. equal to the phase current D. 1.732 times the phase current

D

In series as well as parallel resonant circuits, increasing the value of resistance would lead to A. increase in the bandwidth of both the circuits B. decrease in the bandwidth of both the circuits C. increase in bandwidth in series circuit and decrease in parallel circuit D. decrease in bandwidth in series circuit and increase in parallel circuit

D

Power in a three phase star system is equal to A. √3 × VL × IL × power factor B. 3 × Vph × IL × power factor C. 3 × VL × Iph × power factor D. 3 x Vph x Iph x power factor

D

The phase angle of a series RL circuit may be computed ______ as _______ or _______ or _______. A. cos -1 R/XL, sin -1 XL /R, tan -1 R/Z B. cos -1 R/Z, sin -1 XL /R, tan -1 R/XL C. cos -1 Z/XL, sin -1 R/Z, tan -1 XL /R D. cos -1 R/Z, sin -1 X L/Z, tan -1 X L/R

D

The value of current at resonance in a series RLC circuit is affected by the value of A. R B. C C. L D. all of these

D

Which of the following theorems enables a number of voltage (or current) source to be combined directly into a single voltage (or current) source? A. compensation theorem B. reciprocity theorem C. superposition theorem D. Millman's theorem

D

Kirchhoff's voltage law is not valid for a non-linear network

False

A closed path made of several branches of the network is known as

loop