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The correct ANSWER is (a) Hyperbolic

Best explanation: The shape of the speed-armature CURRENT characteristics in DC SERIES motor is hyperbolic. The motor EQUATION is Eb=Vt-IaRa=Km∅ωm. N=(Vt/KmIa)-Ra/Km. N∝1÷Ia.

The correct option is (a) 5 Wb

To EXPLAIN I would say: In DC series motor, FIELD WINDINGS are CONNECTED in series with the armature circuit. F=NIa=R∅. Ia∝∅. ∅=F÷R=5 wb.

The correct choice is (a) Separately excited motor

The explanation: In dynamic braking, DC SERIES motor behaves as a separately excited motor as the motor ARMATURE is disconnected from the source and CONNECTED across RESISTANCE RB.

The correct ANSWER is (b) 1 SEC

Easiest EXPLANATION: The fundamental time period of the cot WAVE is π. The time period of x(t) is a π÷π=1 sec. The time period is INDEPENDENT of phase shifting and time shifting.

Correct ANSWER is (a) True

Explanation: For faster braking, the series field is separated from the ARMATURE circuit. The series field is EXCITED by a different voltage SOURCE.

Correct option is (a) True

To elaborate: In series DC MACHINE, the field WINDING is in series with the armature winding. The armature current FLOWS through the field winding. F=NIa=R∅. Ia∝∅.

Right choice is (a) Magnetic FIELD

Explanation: Dynamic BRAKING requires a strong magnetic field to convert energy from the magnetic domain into the ELECTRICAL domain. The KINETIC energy is wasted at a higher rate.

Right choice is (c) 1

Easy explanation: The QUALITY factor is defined as the ratio of the reactive POWER to the ACTIVE power CONSUMED. The resistor always ABSORBS active power and capacitor absorbs the reactive power. Quality factor=1÷RC=1÷1=1.

Correct option is (a) 1 rad/s^2

The best explanation: Using the dynamic EQUATION of MOTOR J×(angular acceleration) = Motor TORQUE – LOAD torque: 1×(angular acceleration) = 2-1=1, angular acceleration=1 rad/s^2.

Right CHOICE is (a) 12 V

Best explanation: Back emf developed in the motor can be calculated using the relation EB = Vt – I×Ra. In question, it is asking for a full load. 20 V is terminal VOLTAGE it is fixed so Eb = 20-10×.8 = 12 V.

The correct option is (b) 1

For EXPLANATION I would say: The coefficient of COUPLING expresses how the two coils are magnetically coupled. It is mathematically represented as K=M÷√L1.L2. For tightly coupled coils, the VALUE of the mutual INDUCTANCE is √L1.L2. The value of the coefficient of coupling is 1.

Right choice is (a) VO

To EXPLAIN I would SAY: The Vc(t)=Vo(1- e^-t) is Vo is the TRANSIENT equation of the capacitor Voltage. At the steady state (t=∞) Vc(t)=Vo(1- e^-∞) is Vo. The maximum Voltage ACROSS the capacitor is Vo.

Correct answer is (a) .5 rad/sec

To elaborate: During resonance CONDITION XL=Xc. The VALUE of the resonant FREQUENCY is 1÷√LC=1÷√4=.5 rad/sec. The VOLTAGE across the capacitor and INDUCTOR becomes equal.

Right choice is (a) Neither even nor ODD

Explanation: NENO stands for Neither even nor odd. The FUNCTIONS which are not the mirror image of the y-axis and nor SYMMETRIC about the origin are NENO functions.

The correct option is (a) True

The EXPLANATION: The EVEN functions are those functions which are a mirror image of the y-axis. The cosine function is an even function WHOSE time period is 2π.

Correct choice is (b) 0 MW

The best explanation: The resistor is a LINEAR element. It only absorbs real power and dissipates it in the form of heat. The voltage and CURRENT are in the same phase in case of the resistor so the ANGLE between V & I is 0^o. P=I^2R=0×0×0=0 MW.

The CORRECT answer is (a) -240 W

To EXPLAIN I would say: When the current enters the positive terminal of an ELEMENT it will always absorb the power and when the current leaves the positive terminal it will deliver the power. Power delivered is -30×8=-240 W.

The correct option is (a) 60 V

Explanation: During the resonance CONDITION XL=Xc. The value of the capacitor VOLTAGE is Q×Vs. The power factor of the circuit is ONE. Vc=20×3=60 V.

The correct option is (c) 0.2

To EXPLAIN I would say: The power factor is defined as the ratio of ACTIVE power to the APPARENT power. COS(φ)=R÷Z=2÷10=.2. It has no unit.

Right choice is (b) 0 Hz

For explanation I would SAY: The FREQUENCY is defined as the NUMBER of oscillations per second. It is reciprocal of the time PERIOD. DC supply magnitude is constant. It does not change with time so the frequency of DC supply is 0 Hz.

The CORRECT answer is (a) 1000 SEC

Explanation: The time period is defined as the time after the signal repeats itself. It is EXPRESSED in SECOND. T = 1÷F=1÷.001=1000 sec.

Right choice is (b) 1.4 m/s

Easy EXPLANATION: The VELOCITY of the ball can be calculated USING the relation V=Ω×r. The velocity is the vector product of angular speed and RADIUS. V = Ω×r = 7×.2 = 1.4 m/s.

Correct CHOICE is (a) True

Best explanation: Bounded SYSTEMS are those systems which have some finite maximum value and are DECAYING functions. TRANSIENT analysis is only applicable to bounded signals as they achieve steady state after some TIME.

The CORRECT option is (a) R.M.S

The best I can EXPLAIN: PHASORS are the rotating VALUES which rotate with some angular frequency Ω. The length of the phasor value is r.m.s value.

Right ANSWER is (a) True

Easiest EXPLANATION: The 3-φ system is more economical than 2-∅ system because of no vibrations in power WAVEFORM. The instantaneous power in the 3-∅ system is constant. P=3VpIpcos(φ)=√3VLILcos(∅).

Right CHOICE is (d) RL=Rth

Best EXPLANATION: The condition for maximum power transfer theorem is load should be variable and RL=Rth. During maximum power transfer condition VOLTAGE across load becomes half of THEVENIN voltage and efficiency becomes 50 %.

Correct CHOICE is (d) 0.5

Best explanation: The quality FACTOR is defined as the ratio of the REACTIVE power to the active power CONSUMED. The resistor always ABSORBS active power and capacitor absorbs the reactive power. Quality factor=1÷RC=1÷2=.5.

Right option is (C) 4 Ω

Explanation: When TWO RESISTANCES are connected in parallel their equivalent resistance is EQUAL to the harmonic mean of the individual resistances. Req=R1.R2÷(R1+R2)=8×8÷(8+8)=4 Ω.

Right ANSWER is (b) Inductive COILS

To explain I would say: QUALITY factor is calculated for inductive coils, not for power factor LOADS. Its value determines the quality of the inductor or capacitor. It shows how good an inductor or capacitor can absorb reactive power.

The correct option is (b) 17 H

Easy explanation: The equivalent inductance for series subtracting of two coils is Leq=L1+L2-2M=14+5-2=17 H. The value of equivalent inductance decreases due to NEGATIVELY mutually induced e.m.f in case of the MAGNETICALLY COUPLED circuit.

Right OPTION is (a) 0

Explanation: The COEFFICIENT of coupling EXPRESSES how the two coils are magnetically coupled. It is mathematically represented as K=M÷√L1.L2. For the isolated coils, the VALUE of the mutual inductance is 0. The value of the coefficient of coupling is 0.

Correct CHOICE is (a) Initial

For explanation I WOULD say: The NATURAL RESPONSE is due to the initial conditions PRESENT in the circuit. The natural response is a complete part of the transient response. It is mathematically represented as y(t)=yo×e^-at.

Correct answer is (d) Non-linear, UNILATERAL, Active

For explanation: The nature of the element is non-linear, unilateral and active. The shape of the CHARACTERISTIC is parabolic. For bilateral nature, it should be symmetrical in the first and third quadrant. Its SLOPE is negative in the SECOND quadrant which DETERMINES its active nature.

Right OPTION is (a) True

The EXPLANATION: TRANSIENT response is a primary response in the circuit. It is a temporary response which dies out at t=infinity. It CONSISTS of exponential decaying functions.

Right answer is (a) DIRECT torque control

Explanation: DTC stands for Direct torque control. DTC and IFOC are the TECHNIQUES USED for controlling the speed and torque of a 3-phase induction MOTOR.

The CORRECT answer is (a) True

The explanation: The steady-state response is a PART of the FORCED response. The forced response is due to the electrical source present in the circuit. Its MATHEMATICAL equation involves the source present in the circuit.

Correct option is (a) 2

To explain: The order of the circuit is the NUMBER of memory/storing ELEMENTS which are non-separable present in the circuit. In mathematics, the order is defined as the highest order derivate in the differential equation. The order of the circuit is 2.