BEL Trainee Engineer Electrical Mock Test - 7 - Electrical Engineering (EE) MCQ

Concept:

A decoder is a combinational circuit that converts n lines of input into 2ⁿ lines of output.

Decoder expansion

n₁ × m₁ → n₂ × m₂

D₁ D₂

Number of D₂ decoder required is given as:

∑ K = K1 + K2 + K3 + ------

Calculation:

Given decoder 1 is 3 × 8 and the second decoder is 5 × 32

Number of 3 × 8 decoders = 4 + 0

Number of 3 × 8 decoders = 4

The implementation is shown below.

Important Point

Concept:

The magnetic field forms a closed loop, i.e. the amount of field leaving a point equals the amount entering. i.e. Magnetic monopoles do not exist.

Since the divergence of a field gives the net outflow of a field and is calculated as

B = Magnetic flux density

Since B is related to H (magnetic field intensity) as:

B = μH

∇.H = 0 as well.

Calculation:

∇.B = 0

4 + 2K = 0

K = -2

Important Point

Maxwell’s Equations in Differential Form are as shown:

Insulated Gate Bipolar Transistor (IGBT) is a three-terminal power semiconductor device primarily used as an electronic switch. It is a 4 layer PNPN device that combines an insulated gate N-channel MOSFET input with a PNP BJT output in a type of Darlington configuration.

​Insulated gate Bipolar Transistor is also known as Conductivity-Modulated Field Effect Transistor.

Advantages:

• The insulated gate bipolar transistor (IGBT) is easy to turn ON and OFF.
• The switching frequency is higher than that of power BJT.
• It has a low on state power dissipation.
• It has simpler driver circuit.

Disadvantages:

• The switching frequency of insulated gate bipolar transistor (IGBT) is not as high as that of a power MOSFET.
• High turn-off time
• It cannot block high reverse voltages.

When V_i < 5, the diode becomes OFF.

At this condition, the circuit becomes

Output voltage (V₀) = 5 V

When V_i > 5, diode becomes ON.

At this condition, the circuit becomes

Output voltage (V₀) = V_i

Now, the output waveform will be as shown below.

The maximum value of output voltage = 10 V

The minimum value of output voltage = 5 V

Important Point:

• This circuit is basically a negative series clipper.
• In negative series clipper, the negative voltage value is clipped with help of a series diode.

Damping system:

• Damping System is that part of the instrument which provides damping force to damp the oscillations of the pointer before it comes to rest.
• Because of inertia, the pointer of the instrument oscillates around its final deflected position for some time before coming to rest.
• Damping force acts as a brake to prevent these oscillations of the moving system and brings the pointer to it's final deflected position quickly.

Methods of damping are:

Air friction 'or' pneumatic damping:

• In this system, a light aluminum piston is attached to the spindle of the instrument and is arranged to move in a fixed air chamber closed at one end.
• The compression and suction action of the piston on the air in the chamber damp the possible oscillations of the moving system.

Eddy current damping 'or' Electromagnetic Damping:

• It is the most efficient type of damping.
• In this type of damping, a thin disc usually of copper 'or' aluminum is mounted on the spindle. When this disc moves in the magnetic field of the permanent magnet, the line of force are being cut and eddy current is produced.
• The force that exists between these current and magnetic fields is always in the direction opposing the motion and therefore, provide necessary damping.

Fluid friction damping:

• In this method of damping, a light disc is attached to the spindle of the moving system and completely submerge in the damping oil in a pot.
• The motion of the disc is always opposed by a frictional drag on the disc.

Note:

Spring control method is used to produce controlling torque for measuring instrument.

Points to remember:

Concept:

The energy consumed by a bulb in a time t is given by

E = power (P) × time (t) units

1 unit of electrical energy = 1 kWh

Calculation:

Power rating of bulb (P) = 100 W

Average hours in a day = 10 hours

Total hours in a week = 10 × 7 = 70 hours

The weekly consumption of energy = 100 × 70 = 7 kWh = 7 units

Concept:

The string efficiency is defined as the ratio of voltage across the string to the product of the number of strings and the voltage across the unit adjacent string.

String efficiency = (conductor voltage)/(number of discs × voltage across the disc nearest to the conductor)

For the adequate performance of transmission line, it is essential that the voltage distribution across the line should be uniform. This can be achieved by the following methods.

1) Use of longer cross arm

2) Capacitive grading

3) By using grading rings or static shielding

Calculation:

Given that,

Let the total voltage = V

Voltage across the bottom most unit = 0.33V

Number of insulators (n) = 4

String efficiency

The output of the single-phase voltage-source-square wave inverter, i.e. a square wave is fed to the inductive load.

The current in the inductor is given by therefore when square voltage is

input the inductor current will be triangular.

Phasor quantities used in different voltage regulation methods are given below.

Synchronous impedance method – EMF phasor

MMF method – MMF phasor

Zero power factor (ZPF) method – both EMF and MMF phasors

American Standard association method – EMF and MMF phasors including saturation

Important Points:

Synchronous impedance method:

• The synchronous impedance method of calculating voltage regulation of an alternator is otherwise called the EMF method.
• The synchronous impedance method or the EMF method is based on the concept of replacing the effect of armature reaction by an imaginary reactance.
• It gives a result that is higher than the original value. That's why it is called the pessimistic method.
• For calculating the regulation, the synchronous method requires the armature resistance per phase, the open-circuit characteristic and the short circuit characteristic.

Armature turn method:

It is also known as the MMF method. It gives a value which is lower than the original value. That's why it is called an optimistic method.

To calculate the voltage regulation by MMF Method, the following information is required. They are as follows:

• The resistance of the stator winding per phase
• Open circuit characteristics at synchronous speed
• Field current at rated short circuit current

Potier triangle method (ZPF):

• This method depends on the separation of the leakage reactance of armature and their effects.
• It is used to obtain the leakage reactance and field current equivalent of armature reaction.
• It is the most accurate method of voltage regulation.
• For calculating the regulation, it requires open circuit characteristics and zero power factor characteristics.

Concept:

Plug Setting Multiplier (PSM): It is the ratio between the actual fault current in the relay operating coil to pick up current or the relay current setting.

• Plug setting multiplier (PSM) Indicates the severity of the fault.
• The plug setting multiplier is used only in Electromagnetic relays not in numerical relays.
• The operating Times of the Relay operation are depending upon the PSM. The high value of PSM indicates low operating time.

Calculation:

Given that, fault current = 2000 A

current setting = 0.5 × 5 = 2.5

PSM =

= 10

Concept:

Bilateral Laplace transform:

Unilateral Laplace transform:

Some important Laplace transforms:

Differentiation in the frequency domain:

Calculation:

By applying frequency differentiation property,

Feedback Systems:

There are 4 possible combinations for Voltage and Current with which we can sample at the output and mix the feedback to the input.

Sampling:

• At the output side, we will take a sample of output since we want to check the behavior of output and we don't want to disturb the output when we take the sample.
• That's why when the voltage is sampled, it is in parallel (as the voltage is the same in parallel/shunt) and current in series (as the current is the same in series).

Mixing:

• In the mixing end we want to affect the signal that is provided to the amplifier since that is the actual fundament of giving the feedback.
• So, the voltage will be in series and the current will be in parallel (shunt). So that they can change the input and effect the change in output.

The four basic feedback topologies are as shown:

i) Voltage-sampling voltage-mixing (series-shunt) topology.

ii) current-sampling voltage-mixing (series-series) topology.

iii) current-sampling current-mixing (shunt-series) topology.

iv) voltage-sampling current-mixing (shunt-shunt) topology.

Explanation:

In the given case voltage is sampled and current is mixed so it is Voltage shunt feedback.

Necessary and sufficient condition to prove the linearity of the system is that linear system follows the laws of superposition i.e. the response of the system is the sum of the responses obtained from each input considered separately.

For system, y = 2x

If input is ax₁ is applied to the system, then corresponding output is y₁

y₁ = 2ax₁

If input is bx₂ is applied to the system, then corresponding output is y₂

y₂ = 2bx₂

Now If input (ax₁ + bx₂) is applied to the system then corresponding output is

y = 2(ax₁ + bx₂) = 2ax₁ + 2bx₂

⇒ y = y₁ + y₂

Hence above system follows the laws of superposition.

Therefore, above system y = 2x is a linear system.

Short trick:

Conditions to check whether the system is linear or not.

• The output should be zero for zero input
• There should not be any non-linear operator present in the system

Examples of non-linear operators are:

a. Trigonometric operators- sin, cos, tan, cot, sec, cosec, etc.

b. Exponential, logarithmic, modulus, square, cube etc.

For the system to be linear neither input x nor output y should have any of these non-linear operators.

Above systems and are non-linear systems as both involve cube and square operators respectively.

System y = x + 1 is also a non-linear system as the output is nonzero for zero input.

Hence, only y = 2x is linear system.

Tunnel diode characteristics

In Region between Peak Point & valley Point the current in Tunnel diode decrease with increase in forward Bias voltage. Thus Tunnel diode shows -ve resistance between peak point & valley point

• Abject means Terrible without hope, without any pride and respect for yourself.
• Challenge means something new and difficult that forces you to make a lot of effort
• Miserable means very unhappy
• Deny means to state that something is not true; to refuse to admit or accept something
• Disobey means to refuse to do what you are told to do

Hence Correct Answer is Option B

Repeal: To revoke or annul a law, regulation, or decision, typically through official or legislative means.

1. Sanction:

   • As a verb: to give official permission or approval for an action.
   • As a noun: a penalty or measure taken against someone who has violated a rule or law.

2. Perpetuate: To make something continue indefinitely; to sustain or prolong.

3. Pass:

   • As a verb: to approve or adopt a proposal or legislation.
   • As a noun: a successful attempt to achieve something; also, a document or ticket granting authorization or access.

4. Cancel: To revoke or annul something previously scheduled, arranged, or agreed upon; to declare null and void.

Correct option D

To group non-contiguous worksheets in Microsoft Excel, you can use the following method:
1. The Ctrl key and mouse:
- Open Excel and go to the worksheet tab bar at the bottom of the Excel window.
- Hold down the Ctrl key on your keyboard.
- Click on the first worksheet tab that you want to include in the group.
- While holding down the Ctrl key, click on the other worksheet tabs that you want to include in the group. You can select multiple non-contiguous worksheets using this method.
- Release the Ctrl key after selecting all the desired worksheets.
- The selected worksheets will now be grouped together.
Note: When you group non-contiguous worksheets, any actions or changes you make to one worksheet will apply to all the grouped worksheets simultaneously.
It is important to note that the other options mentioned in the question are not the correct methods to group non-contiguous worksheets:
- The group button on the standard toolbar (Option A) is used to group contiguous worksheets, not non-contiguous ones.
- The shift key and the mouse (Option B) is used to select a range of contiguous worksheets, not non-contiguous ones.
- The alt enter key (Option D) is used to insert a line break within a cell, and it is not related to grouping worksheets.
Therefore, the correct answer is Option C: The Ctrl key and mouse.

The protocol that provides virtual terminal in the TCP/IP model is Telnet.
Telnet:
- Telnet is a network protocol that allows users to remotely access and control a virtual terminal over a TCP/IP network.
- It provides a command-line interface that enables users to execute commands and interact with remote hosts as if they were directly connected to them.
- Telnet uses TCP as the underlying transport protocol to establish a reliable connection between the local and remote hosts.
- It operates on port number 23 and sends data in clear text format, which means it is not secure for transmitting sensitive information.
- Telnet allows users to remotely manage devices, troubleshoot network issues, and administer systems without physically being present at the location.
Other options:
- SMTP (Simple Mail Transfer Protocol) is a protocol used for sending and receiving email messages.
- HTTP (Hypertext Transfer Protocol) is a protocol used for transmitting web pages and other resources over the internet.
- None of these options provide a virtual terminal functionality in the TCP/IP model.
Therefore, the correct answer is Telnet (option A).

To solve this problem, we need to follow these steps:
1. Select Rows 5 and 6: This means we need to highlight or select both Row 5 and Row 6 in the spreadsheet.
2. Choose "Insert" > "Row": Navigate to the menu bar and click on the "Insert" option. From the drop-down menu, select "Row" to insert new rows.
Based on the given question, the correct answer is option A: 2 Rows will be inserted after Row 4. Here's why:
- When we select Rows 5 and 6, it means we are choosing to insert new rows after these selected rows.
- Since Row 5 is before Row 6, inserting rows after Row 4 means that the new rows will be inserted after Row 4 and before Row 5.
- Therefore, the new rows will be inserted after Row 4 but before Row 5, resulting in 2 rows being inserted after Row 4.
In summary, selecting Rows 5 and 6 and choosing to insert rows will add 2 new rows after Row 4.

The File System Used by Windows 95

Windows 95 typically uses the FAT16 file system.

Explanation:

• FAT16: The File Allocation Table (FAT) is a file system used by older versions of Windows, including Windows 95. The number 16 refers to the maximum number of bits used to store addresses of data clusters on the hard drive.


• FAT32: While FAT16 was the default file system for Windows 95, it was later replaced by FAT32 in newer versions of Windows, such as Windows 98 and Windows ME. FAT32 allows for larger partition sizes and improved file management.


• NTFS: Windows 95 does not natively support the NTFS file system. NTFS (New Technology File System) was introduced with Windows NT and is used in newer versions of Windows, such as Windows 2000, Windows XP, and beyond. NTFS offers enhanced security, reliability, and support for larger file sizes and volumes.


• LMFS: LMFS is not a file system used by Windows 95 or any other Windows operating system. This option is incorrect.

In summary, the file system typically used by Windows 95 is FAT16.

Retaining Information when Power is Turned Off:
ROM (Read-Only Memory)
- ROM is a non-volatile memory type that retains data even when the power is turned off.
- It contains firmware or software instructions that are permanently stored during manufacturing.
- The data stored in ROM is not easily modified or erased, hence the name "read-only."
CPU (Central Processing Unit)
- The CPU is the brain of the computer that performs calculations and executes instructions.
- It does not retain any data when the power is turned off.
- The CPU relies on other storage devices, such as RAM and ROM, to store and retrieve data.
DRAM (Dynamic Random-Access Memory)
- DRAM is a type of volatile memory that requires constant power to retain data.
- When the power is turned off, the stored data in DRAM is lost.
- DRAM is commonly used as the main memory in computers due to its fast access times.
DIMM (Dual In-Line Memory Module)
- DIMM is a physical component that houses memory modules, such as RAM or ROM.
- It does not retain any data when the power is turned off.
- The data stored in DIMM is stored in the memory modules it houses, which may be either volatile (e.g., RAM) or non-volatile (e.g., ROM).
Conclusion:
Of the options provided, only ROM (Read-Only Memory) retains the information it's storing when the power to the system is turned off.

The answer to the question is B: Resolution.

Resolution refers to the pixel spacing or the level of detail that can be displayed or captured by a digital device. It is an important factor in determining the clarity and sharpness of images.

Here are some key points to understand about resolution:

• Resolution is measured in pixels per inch (PPI) or dots per inch (DPI). It indicates the number of pixels or dots that can be displayed in one inch of a digital image.


• Higher resolution means more pixels or dots per inch, resulting in greater detail and sharper images.


• Lower resolution means fewer pixels or dots per inch, resulting in less detail and more pixelation.


• Resolution is a crucial factor in various digital devices, such as computer monitors, cameras, printers, and smartphones.


• For example, a higher resolution in a camera allows for capturing more details in an image, while a higher resolution in a monitor provides a clearer and more detailed display.


• Resolution is often expressed as the width and height of an image in pixels, such as 1920x1080 for Full HD or 3840x2160 for 4K Ultra HD.

Therefore, in the context of pixel spacing, the correct answer is B: Resolution.

Special Effects for Drawing Objects:
The special effects that can be applied to drawing objects include:
1. Gradient Fills: Gradient fills allow you to apply a smooth transition of colors to a shape or object. This effect can be used to create depth, shading, and visual interest in your drawings.
2. Line Color and Style: You can change the color and style of lines in your drawings to add emphasis or create different visual effects. For example, you can use dashed or dotted lines to create a sense of movement or highlight specific areas.
3. Rotating: Rotating an object allows you to change its orientation. This effect can be used to create dynamic compositions or adjust the positioning of objects within your drawing.
Overall, the answer is All of these (option D) as all the mentioned options include special effects that can be applied to drawing objects.

After moving a clip art image to a particular location on the slide, you can immediately reverse the action using the following steps:
Step 1: Identify the options available to reverse the action.
There are several options available to reverse the action of moving a clip art image on a slide:
- Click the "Undo" button
- Click the "Redo" button
- Use the "Not do move object" command on the "Edit" menu
Step 2: Determine the correct option to reverse the action.
In this case, the correct option is to click on the "Undo" button.
Step 3: Execute the correct option to reverse the action.
To reverse the action of moving a clip art image to a particular location on the slide, follow these steps:
1. Locate the "Undo" button, which is typically represented by a curved arrow pointing to the left.
2. Click on the "Undo" button.
Step 4: Verify that the action has been successfully reversed.
After clicking on the "Undo" button, the clip art image should be moved back to its previous location on the slide.
Conclusion:
By following the above steps and clicking on the "Undo" button, you can immediately reverse the action of moving a clip art image to a particular location on the slide.

The name of the form used to input chart values is: Datasheet
- Datasheet: A datasheet is a form used to input chart values in various software applications.
- Microsoft Excel: Although Microsoft Excel is a popular software application for creating charts, it is not the name of the specific form used to input chart values.
- Microsoft Graph: Microsoft Graph is a service that allows developers to access data from various Microsoft services, but it is not the name of the form used to input chart values.
- Auto form: Auto form is not the name of the form used to input chart values.
In conclusion, the correct answer is Datasheet, which is the name of the form used to input chart values.

Why a computer cannot "boot" without an operating system:

• Definition of "boot": Booting refers to the process of starting up a computer and loading the necessary software to make it ready for use.


• Primary functions of an operating system: The operating system (OS) is responsible for managing all the hardware and software resources of a computer, and it performs several essential functions during the boot process:




• Hardware initialization: The OS initializes and configures all the hardware components of the computer, such as the processor, memory, storage devices, and input/output devices.


• Device drivers: The OS loads the necessary device drivers, which are software programs that enable communication between the operating system and the hardware devices.


• File system management: The OS mounts the file system, allowing it to access and organize the files stored on the storage devices.


• Process management: The OS creates and manages processes, which are the executing instances of programs, allowing multiple programs to run concurrently.


• User interface: The OS provides a user interface that allows users to interact with the computer, whether through a graphical interface or a command-line interface.




• Boot process: The boot process involves several steps, including:




• Power-on self-test (POST): The computer's firmware (BIOS or UEFI) performs a diagnostic test to check the hardware components and ensure they are functioning properly.


• Bootloader: The firmware locates and executes the bootloader, which is responsible for loading the operating system into memory.


• Operating system: The bootloader transfers control to the operating system, allowing it to take over and continue the boot process.




• Conclusion: Without an operating system, the computer would not have the necessary software to manage its hardware resources, provide a user interface, or execute programs. Therefore, a computer cannot "boot" without an operating system.

ARP (Address Resolution Protocol) is:
- A TCP/IP protocol used to dynamically bind a high level IP address to a low-level physical hardware address:
- ARP is a protocol used in TCP/IP networks to map an IP address to a corresponding physical MAC address.
- It allows devices on a local network to communicate with each other using their hardware addresses.
- ARP resolves IP addresses to MAC addresses on the same network segment.
- A TCP/IP high-level protocol for transferring files from one machine to another:
- This statement is incorrect. ARP is not used for file transfer; it is specifically used for address resolution.
- A protocol used to monitor computers:
- This statement is incorrect. ARP is not used for monitoring computers. It is solely used for address resolution.
- A protocol that handles error and control messages:
- This statement is incorrect. ARP is not responsible for handling error and control messages. It is solely used for address resolution.
Conclusion:
The correct answer is A: A TCP/IP protocol used to dynamically bind a high-level IP address to a low-level physical hardware address. ARP is essential for communication within a local network, allowing devices to find each other using their IP and MAC addresses.

IEEE 802.3ab and Gigabit Ethernet over UTP cabling
IEEE 802.3ab:
IEEE 802.3ab is a standard that defines the specifications for Gigabit Ethernet transmission over various types of cabling. It is also known as 1000BASE-T.
Gigabit Ethernet over UTP:
Gigabit Ethernet is a networking technology that provides data transmission at a rate of 1 gigabit per second (Gbps). It can be transmitted over various types of cabling, including unshielded twisted pair (UTP) cables.
UTP Category 5, 5e, and 6:
UTP cables are commonly used for Ethernet networking. They consist of four pairs of twisted copper wires. The different categories of UTP cables indicate their performance characteristics, with higher categories providing better performance.
- Category 5: This is the most basic type of UTP cable and supports data transmission up to 100 megabits per second (Mbps).
- Category 5e: This enhanced version of Category 5 cable supports data transmission up to 1000 Mbps, making it suitable for Gigabit Ethernet.
- Category 6: This is an improved version of Category 5e cable and offers even better performance. It also supports data transmission up to 1000 Mbps.
1000 BASE-T:
1000BASE-T is the Gigabit Ethernet standard defined by IEEE 802.3ab for transmission over UTP cabling. It specifically refers to Gigabit Ethernet over Category 5, 5e, or 6 UTP cables.
Answer:
Therefore, the correct answer is A: 1000 BASE-T, as defined by IEEE 802.3ab, for Gigabit Ethernet transmission over UTP Category 5, 5e, or 6 cabling.

Checking Statement I:
Using the above references, we get the following arrangement:

Since there is no information about the position of Bhanu so we cannot find the person who sits on the immediate right of Bhanu.

Hence, data in statement I alone is not sufficient.
Checking Statement II:
Using the above references, we get the following arrangement:

Clearly, Prakash sits on the immediate right of Bhanu.

Hence, data in statement II alone is sufficient.

Hence, Option B is correct.