1.
For satellite the source of energy is........
Correct Answer
C. Solar cell
Explanation
The correct answer is solar cell because satellites rely on solar panels to convert sunlight into electricity. These solar cells are made up of photovoltaic materials that absorb photons from the sun and generate an electric current. This energy is then used to power the various systems and instruments on the satellite, including communication devices, sensors, and scientific instruments. Solar cells are preferred as a source of energy for satellites because they provide a sustainable and renewable source of power in space.
2.
The output of solar cell is of the order of........
Correct Answer
A. 1 W
Explanation
The output of a solar cell is typically around 1 W. Solar cells convert sunlight into electricity through the photovoltaic effect. The efficiency of solar cells varies, but on average, they can produce around 1 watt of power per square meter of solar panel. This output can be affected by factors such as the angle and intensity of sunlight, temperature, and the quality of the solar cell itself.
3.
Gain of an amplifier = 400, input signal to an amplifier = 0.5 cos (313 t). The output signal is represented as
Correct Answer
A. 20 sin (403 t)
Explanation
The output signal of the amplifier is represented as 20 sin (403 t). This means that the output signal is a sine wave with an amplitude of 20 and a frequency of 403 t. The gain of the amplifier is not affecting the frequency or phase of the signal, only the amplitude. Therefore, the correct answer is 20 sin (403 t).
4.
Microwave energies propagate the length of the waveguide by __________ its side walls.
Correct Answer
A. Refraction off
Explanation
Microwave energies propagate the length of the waveguide by refracting off its side walls. Refraction is the bending of waves as they pass from one medium to another, and in this case, the microwave energies are bending as they encounter the side walls of the waveguide. This phenomenon allows the microwaves to travel along the waveguide and propagate efficiently. Reflection off the side walls would result in the microwaves bouncing back, while moving off would imply that the microwaves are leaving the waveguide entirely. None of the above options accurately describe how microwave energies propagate in a waveguide.
5.
Two entities that are combined to form a Magic Tee ar
Correct Answer
B. One H? and one E plane tee
Explanation
The correct answer is "One H? and one E plane tee." A Magic Tee is a type of microwave component that combines two signals. It consists of one H-plane tee and one E-plane tee. The H-plane tee divides the signal into two equal parts, while the E-plane tee combines the signals in a specific way to achieve the desired output. Therefore, the combination of one H-plane tee and one E-plane tee is necessary to form a Magic Tee.
6.
Consider reciprocal of capacitance and torsional spring stiffness as analogous quantities. The system is considered as
Correct Answer
C. Force - voltage
Explanation
In this analogy, the reciprocal of capacitance is analogous to torsional spring stiffness. In the electrical system, force is analogous to voltage. This means that the force in the mechanical system is analogous to the voltage in the electrical system. Therefore, the correct answer is "Force - voltage".
7.
Under mechanical rotational system and electrical system the quantities that are not analogous are
Correct Answer
D. Moment of inertia and conductance
Explanation
Moment of inertia is a property of a rotating object that determines its resistance to changes in its rotational motion, while conductance is a measure of how easily an electrical current can flow through a material. These two quantities are not analogous because they describe different aspects of different systems - rotational motion and electrical conductivity.
8.
An ideal current source has zero
Correct Answer
B. Internal conductance
Explanation
An ideal current source has zero internal conductance because it is designed to provide a constant current regardless of the load connected to it. Internal conductance refers to the ability of a current source to conduct current internally, which would result in a deviation from the desired constant current output. Therefore, in an ideal current source, there should be no internal conductance to ensure that the current remains constant and unaffected by any internal factors.
9.
To carry a current of 0.3 amperes, a 100 ohm resistor is needed in an electric circuit. A resistor you would select is
Correct Answer
B. 100 ohm, 10 watts
Explanation
The correct answer is 100 ohm, 10 watts because the power (in watts) can be calculated using the formula P = I^2 * R, where P is power, I is current, and R is resistance. In this case, the current is 0.3 amperes and the resistance is 100 ohms. Plugging these values into the formula, we get P = (0.3)^2 * 100 = 0.09 * 100 = 9 watts. Since the power required is 9 watts, the resistor with a power rating of 10 watts is the most suitable choice.
10.
Let T be the time period of a periodic signal x (t) and for some time “t?” let y (t) = x (t - to) + x (t + to). Let b denotes the Fourier series coefficients of y (t). For all odd values of k if b? = 0 then “to” can be equal to
Correct Answer
D. T/4
Explanation
If b_k = 0 for all odd values of k, it means that the Fourier series coefficients for the odd harmonics of y(t) are zero. This implies that y(t) does not contain any odd harmonics in its frequency spectrum.
Given that y(t) = x(t - to) + x(t + to), we can deduce that x(t - to) and x(t + to) have the same Fourier series coefficients for the odd harmonics.
Since the odd harmonics of y(t) are zero, it means that the odd harmonics of x(t - to) and x(t + to) are also zero. This can only happen if the time shift to is equal to T/4, where T is the time period of x(t).
Therefore, "to" can be equal to T/4.
11.
To limit the armature current to 125% of its rated value, the external resistance to be added in the armature circuit is
Correct Answer
D. 31.1 Ω
Explanation
To limit the armature current to 125% of its rated value, a high external resistance needs to be added in the armature circuit. The resistance value should be higher than the armature circuit's internal resistance in order to effectively limit the current. Among the given options, 31.1 Î© is the highest resistance value, making it the correct answer.
12.
A 3-phase synchronous motor is connected to an ac main. The motor runs at full load and unity power factor. With field current held constant if its shaft load is reduced by half, its new power factor will be
Correct Answer
C. Leading
Explanation
When the shaft load of a 3-phase synchronous motor is reduced by half while keeping the field current constant, the motor will operate at a leading power factor. This means that the current will lead the voltage in the circuit. This change in power factor occurs because the motor is now operating at a higher excitation level than before, causing the current to lead the voltage. The power factor of a synchronous motor is dependent on its excitation level, and reducing the shaft load while keeping the field current constant increases the excitation level, resulting in a leading power factor.
13.
The vertical distance between the axis of the beam before and after loading at a point is called as
Correct Answer
B. Deflection
Explanation
Deflection refers to the vertical distance between the axis of a beam before and after loading at a specific point. It is a measure of how much the beam bends or flexes under the applied load. Deformation, on the other hand, is a more general term that refers to any change in shape or size of an object. Slope is not the correct term in this context, as it typically refers to the inclination or steepness of a line or surface. Therefore, the correct answer is deflection.
14.
The wind intensity can be described by
Correct Answer
C. Beaufort number
Explanation
The Beaufort number is used to describe wind intensity based on observations of its effects on land or sea. It is a scale ranging from 0 to 12, with each number corresponding to a specific range of wind speeds and their associated effects. This scale was developed by Sir Francis Beaufort in the early 19th century and is still widely used today. The Beaufort number provides a simple and practical way to communicate wind intensity, making it a useful tool for various applications such as weather forecasting, maritime navigation, and aviation.
15.
The PWM control of DC motor varies
Correct Answer
A. Linearly with speed
Explanation
The PWM control of a DC motor varies linearly with speed because PWM (Pulse Width Modulation) is a technique that adjusts the average voltage applied to the motor by rapidly switching the power on and off. By varying the width of the pulses, the average voltage can be adjusted, which in turn controls the speed of the motor. As the width of the pulses increases, the average voltage and speed of the motor also increase in a linear relationship.
16.
Ward-Leonard system of system of speed control is not recommended for
Correct Answer
A. Constant speed operation
Explanation
The Ward-Leonard system of speed control is not recommended for constant speed operation because it is primarily designed for applications that require variable speed control. The system uses a motor-generator set to control the speed of the motor by varying the voltage and frequency. This allows for precise control over the motor's speed, making it ideal for applications where speed needs to be adjusted frequently. However, for constant speed operation, other simpler and more efficient control systems can be used instead.
17.
Mark the wrong option. Which of the following cause and effect behaviour in speed control is correct when field resistance is increased.
Correct Answer
C. Increase in EMF
Explanation
When the field resistance is increased in a speed control system, it leads to a decrease in the flux. This decrease in flux causes a decrease in the electromotive force (EMF) generated in the system. As a result, the speed of the system decreases. Therefore, the option "Increase in EMF" is incorrect as it contradicts the cause and effect relationship described above.
18.
Small DC motors have best speed control by
Correct Answer
A. Armature voltage control
Explanation
Armature voltage control provides the best speed control for small DC motors. By adjusting the voltage applied to the armature, the speed of the motor can be controlled effectively. This method allows for precise control over the motor's speed, making it ideal for applications where speed regulation is critical. Field resistance control, on the other hand, is not as effective in providing precise speed control. Therefore, the correct answer is armature voltage control.
19.
The short circuit load losses is/are
Correct Answer
A. Direct load loss and stray load losses
Explanation
The correct answer is direct load loss and stray load losses. Short circuit load losses refer to the losses that occur in a transformer when it is subjected to a short circuit condition. Direct load loss refers to the power loss that occurs in the resistance of the transformer windings when current flows through them. Stray load losses, on the other hand, refer to the losses that occur due to the leakage flux and eddy currents in the transformer's core and windings. Both direct load loss and stray load losses contribute to the overall short circuit load losses in a transformer.
20.
The coupling angle or load angle of a synchronous motor is defined as the space angle between
Correct Answer
A. Rotor and stator poles of opposite polarity
Explanation
The coupling angle or load angle of a synchronous motor is defined as the space angle between the rotor and stator poles of opposite polarity. This angle represents the phase difference between the rotor and stator magnetic fields, which is crucial for the motor's operation. By having opposite polarities, the rotor and stator poles attract each other, creating the necessary torque for the motor to rotate. Therefore, the coupling angle is determined by the positions of these opposite poles, indicating the alignment and interaction between the rotor and stator fields.
21.
Synchronizing power is
(i) Stiffness coefficient of electromagnetic coupling between stator and rotor
(ii) Stability measure of synchronous machine
(iii) Power consumption factor
Correct Answer
A. I,ii
Explanation
The correct answer is i,ii. Synchronizing power refers to the stiffness coefficient of electromagnetic coupling between the stator and rotor in a synchronous machine. It is also a stability measure of the machine, indicating how well it can maintain synchronization with the grid. The power consumption factor, on the other hand, is not related to synchronizing power.
22.
Large stiffness coefficient represents
Correct Answer
A. Motor speed remains practically constant
Explanation
A large stiffness coefficient represents that the motor speed remains practically constant. This means that the motor is able to maintain a consistent speed regardless of any fluctuations or changes in mechanical load. The stiffness coefficient is a measure of the motor's ability to resist changes in speed, and a large value indicates a high level of stability and consistency in the motor's performance.
23.
Consider the below remarks for an alternator
(i) An over excited machine is more stiff
(ii) Machine with longer air-gap is less stable than one with smaller air-gap
Correct Answer
A. (i) is True, (ii) is False
Explanation
An over excited machine refers to an alternator where the field current is increased beyond the normal value, resulting in a stronger magnetic field. This increased magnetic field makes the machine more stiff, meaning it has a higher resistance to changes in its operating conditions. On the other hand, the stability of an alternator is influenced by the air-gap length. A machine with a longer air-gap is less stable compared to one with a smaller air-gap. Therefore, statement (i) is true because an over excited machine is indeed more stiff, while statement (ii) is false because a machine with a longer air-gap is less stable.
24.
Which of the following is/are used in synchronous machines to maintain mechanical stability?
Correct Answer
A. Damper winding
Explanation
A damper winding is used in synchronous machines to maintain mechanical stability. It consists of short-circuited conductors placed in slots on the rotor. When the rotor experiences mechanical disturbances, such as sudden changes in load or faults, the damper winding helps to dampen the oscillations and stabilize the machine. This is achieved by inducing eddy currents in the conductors, which create a magnetic field that opposes the mechanical disturbances. By doing so, the damper winding helps to prevent excessive vibrations and maintain the mechanical integrity of the synchronous machine.
25.
Electromagnetic torque is present in rotating machines when
Correct Answer
A. Both stator and rotor windings carry current
Explanation
Electromagnetic torque is generated in rotating machines when both the stator and rotor windings carry current. This is because the interaction between the magnetic fields produced by the currents in the stator and rotor windings creates a force that causes the rotor to rotate. If only one of the windings carries current, there will be an imbalance in the magnetic fields, resulting in a reduced or no torque production. Therefore, for electromagnetic torque to be present, it is necessary for both the stator and rotor windings to carry current.
26.
The operation of a synchronous motor operating on constant excitation across infinite bus will not be stable if power angle δ
Correct Answer
A. Exceeds internal angle θ
Explanation
If the power angle δ exceeds the internal angle θ, the operation of a synchronous motor operating on constant excitation across an infinite bus will not be stable. This means that the motor will not be able to maintain a steady and synchronized rotation with the power system. The power angle represents the phase difference between the rotor and stator magnetic fields, while the internal angle θ represents the angle between the rotor flux and the resultant air-gap flux. If the power angle exceeds the internal angle, it indicates a loss of synchronization and instability in the motor's operation.
27.
In a synchronous motor the back emf peak set up in the stator depends on
Correct Answer
A. Rotor excitation
Explanation
The back emf peak set up in the stator of a synchronous motor depends on the rotor excitation. The rotor excitation refers to the magnetic field produced by the rotor. As the rotor excitation increases, the strength of the magnetic field also increases, leading to a higher back emf peak in the stator. Therefore, the level of rotor excitation directly affects the back emf peak in a synchronous motor. The other factors mentioned in the options, such as supply voltage, rotor speed, and load on the motor, may have an impact on the motor's performance but do not directly determine the back emf peak.
28.
Who invented the first electricity-generating wind turbine?
Correct Answer
B. Scottish engineer James Blyth
Explanation
James Blyth is credited with inventing the first electricity-generating wind turbine. In 1887, Blyth constructed a wind turbine with cloth sails and a 10-meter rotor diameter, which produced electricity to power his vacation cottage in Marykirk, Scotland. This turbine was a significant milestone in the development of wind power technology and laid the foundation for future advancements in wind energy generation. Blyth's invention paved the way for the widespread use of wind turbines as a renewable energy source.
29.
How many blades does a modern wind turbine have?
Correct Answer
A. 3
Explanation
A modern wind turbine typically has three blades. This design is commonly used because it strikes a balance between efficiency and stability. Having three blades allows the turbine to capture a significant amount of wind energy while still maintaining stability in varying wind conditions. Additionally, three blades are generally easier to manufacture and maintain compared to turbines with a larger number of blades.
30.
Which of these is NOT a part of a modern wind turbine?
Correct Answer
A. Compressor
Explanation
A compressor is not a part of a modern wind turbine. Wind turbines convert the kinetic energy of wind into electrical energy through the use of a rotor, which consists of blades connected to a hub. The blades capture the wind's energy and transfer it to the rotor, which is connected to a generator. The generator then converts the mechanical energy into electrical energy. The other options mentioned (gear box, nacelle, and yaw drive) are all components that are typically found in a modern wind turbine.
31.
How many different components does it take to build a utility scale wind turbine?
Correct Answer
C. More than 8,000
Explanation
A utility scale wind turbine is a complex piece of machinery that requires numerous components to function properly. With the scale and complexity of these turbines, it is reasonable to assume that it takes more than just a few components to build one. The answer "More than 8,000" suggests that the number of components required is significantly high, indicating the intricate nature of utility scale wind turbines.
32.
Roughly how tall are most utility-scale wind turbine towers in the U.S.?
Correct Answer
D. 86 meters (282 feet)
Explanation
Most utility-scale wind turbine towers in the U.S. are approximately 86 meters (282 feet) tall.
33.
What does Heating and cooling of the atmosphere generates?
Correct Answer
C. Convection currents
Explanation
Heating and cooling of the atmosphere generate convection currents. When the air near the Earth's surface is heated, it becomes less dense and rises, creating an upward flow of air. As the heated air rises, it cools down and becomes denser, eventually sinking back down to the surface. This continuous cycle of warm air rising and cool air sinking creates convection currents, which play a significant role in the movement of air and the distribution of heat throughout the atmosphere.
34.
How much is the energy available in the winds over the earth surface is estimated to be?
Correct Answer
B. 1.6 X 107 MW
Explanation
The estimated energy available in the winds over the earth surface is 1.6 X 107 MW. This means that there is a significant amount of energy that can be harnessed from wind power. Wind turbines can convert the kinetic energy of the wind into electrical energy, and with this estimated amount of available energy, wind power has the potential to be a major source of renewable energy.
35.
How much wind power does India hold?
Correct Answer
A. 20,000 MW
Explanation
India holds 20,000 MW of wind power. This means that India has the capacity to generate 20,000 megawatts of electricity from wind energy sources. Wind power is a renewable energy source that is harnessed by using wind turbines to convert the kinetic energy of the wind into electrical energy. India's wind power capacity is significant and contributes to the country's efforts to increase its share of renewable energy in its overall energy mix.
36.
What is the kinetic energy of 1 cubic meter of air moving at the speed of 10 m/s? The density of air is 1.2 kg/m3
Correct Answer
B. 120 J
Explanation
The kinetic energy of an object is given by the formula KE = (1/2)mv^2, where m is the mass of the object and v is its velocity. In this case, we are given the density of air (1.2 kg/m^3) and the velocity (10 m/s). To find the mass, we can use the formula density = mass/volume. Rearranging the formula, we get mass = density * volume. Since the volume is given as 1 cubic meter, the mass is equal to the density. Plugging in the values, we get mass = 1.2 kg. Now we can calculate the kinetic energy using the formula KE = (1/2)mv^2. Substituting the values, we get KE = (1/2)(1.2 kg)(10 m/s)^2 = 60 J. Therefore, the correct answer is 60 J.
37.
The forces, which meet at one point and their lines of action also lie on the same plane, are known as
Correct Answer
A. Coplaner concurrent forces
Explanation
Coplaner concurrent forces are forces that meet at one point and their lines of action also lie on the same plane. This means that the forces are not only acting at the same point, but they are also acting in the same plane. This is in contrast to coplaner non-concurrent forces, which may also lie on the same plane but do not meet at one point. Non-coplaner concurrent forces refer to forces that meet at one point but their lines of action do not lie on the same plane. Non-coplaner non-concurrent forces are forces that neither meet at one point nor lie on the same plane.
38.
Which of the following statement is incorrect?
Correct Answer
D. The velocity ratio of a machine is the ratio of load lifted to the effort applied
Explanation
The velocity ratio of a machine is not the ratio of load lifted to the effort applied. The velocity ratio of a machine is the ratio of the distance moved by the effort to the distance moved by the load.
39.
The centre of gravity of a quadrant of a circle lies along its central radius (r) at a distance of?
Correct Answer
B. 0.6r
Explanation
The center of gravity of a quadrant of a circle lies along its central radius at a distance of 0.6r. This is because the center of gravity of any symmetrical shape lies along its axis of symmetry, which in this case is the central radius. The distance from the center of gravity to the center of the circle is determined by dividing the length of the central radius by the ratio of the area of the quadrant to the area of the entire circle, which is 1/4. Therefore, the distance is 0.6 times the length of the central radius.
40.
Which of the following are vector quantities?
Correct Answer
D. All of these
Explanation
Angular displacement, angular velocity, and angular acceleration are all vector quantities because they have both magnitude and direction. Angular displacement refers to the change in the position or orientation of an object, angular velocity refers to the rate at which the object rotates, and angular acceleration refers to the rate at which the angular velocity changes. Since all three quantities have both magnitude and direction, they can be represented as vectors.
41.
A machine having an efficiency greater than 50%, is known as
Correct Answer
A. Reversible machine
Explanation
A machine having an efficiency greater than 50% is known as a reversible machine. This means that the machine is able to convert a higher percentage of the input energy into useful work output. In a reversible machine, there is minimal energy loss or waste, making it highly efficient.
42.
Which axial force is determined while analyzing a truss?
Correct Answer
C. Both a. and b.
Explanation
When analyzing a truss, both compressive force and tensile force are determined. Compressive force refers to the force that pushes or compresses the structural members of the truss, while tensile force refers to the force that pulls or stretches the members. Both types of forces need to be considered in order to accurately analyze the axial forces acting on the truss.
43.
An object of 30 kg is moved with a velocity of 2 m/s on a horizontal smooth surface. What is the velocity of the block for 4 seconds if force of 40 N is applied on it in the direction of force?
Correct Answer
C. 7.33 m/s
Explanation
The initial velocity of the object is given as 2 m/s. The force applied on the object is 40 N. Using Newton's second law of motion, force = mass x acceleration, we can calculate the acceleration of the object. Rearranging the formula, acceleration = force / mass. Plugging in the values, we get acceleration = 40 N / 30 kg = 4/3 m/s^2. To find the final velocity after 4 seconds, we can use the equation v = u + at, where v is the final velocity, u is the initial velocity, a is the acceleration, and t is the time. Plugging in the values, we get v = 2 m/s + (4/3 m/s^2) x 4 s = 2 m/s + 16/3 m/s = 22/3 m/s = 7.33 m/s. Therefore, the correct answer is 7.33 m/s.
44.
According to the principle of conservation of energy, under the action of _________ force, the sum of P.E and K.E of a particle remains constant.
Correct Answer
A. Conservative force
Explanation
According to the principle of conservation of energy, the sum of potential energy (P.E) and kinetic energy (K.E) of a particle remains constant under the action of a conservative force. A conservative force is a type of force that does not dissipate or remove energy from the system. It can be stored as potential energy and converted into kinetic energy without any loss. Examples of conservative forces include gravitational force and elastic force.
45.
Work done by an engine in 6 sec is 1000 joules. What is the power generated by the engine in watt?
Correct Answer
D. 166 watt
Explanation
The power generated by an engine can be calculated using the formula: Power = Work done / Time taken. In this case, the work done by the engine is given as 1000 joules and the time taken is 6 seconds. Therefore, the power generated by the engine is 1000 joules / 6 seconds = 166 watts.
46.
The range of control of controller __________ due to presence of offset.
Correct Answer
B. Decreases
Explanation
The range of control of the controller decreases due to the presence of offset. Offset refers to the difference between the desired setpoint and the actual process variable. When there is an offset, the controller needs to make adjustments to bring the process variable back to the setpoint. However, if the offset is present, it indicates that the controller is not able to fully control the process within the desired range. Therefore, the range of control decreases.
47.
Shifting of set point and adjusting its new value by the controller, when the value of disturbance increases, is called as_______.
Correct Answer
B. Offset
Explanation
When the value of disturbance increases, the controller adjusts the set point by shifting it to a new value. This adjustment is known as offset. It allows the controller to maintain stability and compensate for the increased disturbance. The term "set-shift" is not commonly used in this context, and "stabilization" refers to the overall goal of maintaining stability rather than the specific action of adjusting the set point. Therefore, the correct answer is offset.
48.
__________ is a structure made of slender members which are joined together at their end points.
Correct Answer
A. Space Truss
Explanation
A space truss is a structure made of slender members that are joined together at their end points. The term "space" refers to the three-dimensional nature of the truss, as it can extend in multiple directions. Trusses are commonly used in engineering and architecture to provide stability and support for various structures such as bridges and roofs. By distributing the load along the members, a space truss can efficiently transfer forces and maintain structural integrity.
49.
Find the force in the member RQ.
Correct Answer
B. 450N
Explanation
Based on the given information, the force in the member RQ is 450N.
50.
_________ trusses lie on a 3D volume.
Correct Answer
D. 3D
Explanation
Trusses are structural elements that consist of straight members connected at joints. They are typically used to support roofs, bridges, and other structures. In this context, trusses are three-dimensional because they exist in a 3D volume. This means that they have length, width, and height, and can span across multiple planes. Therefore, the correct answer is 3D.