BEL Trainee Engineer Electronics Mock Test - 9 - Electronics and Communication Engineering (ECE) MCQ

Half Adder using NAND Gates:

The half adder can also be designed with the help of NAND gates. NAND gate is considered as a universal gate. A universal gate can be used for designing any digital circuitry. It is always simple and efficient to use the minimum number of gates in the designing process of our circuit. The minimum number of NAND gates required to design a half adder is 5.

• The first NAND gate takes the inputs which are the two 1-bit numbers.
• The resultant NAND-operated inputs will be again given as input to 3- NAND gates along with the original input. 
• Out of these 3 NAND gates, 2-NAND gates will generate the output which will be given as input to the NAND gate connected at the end.
• The gate connected at the end will generate the sum bit. Out of the 3 considered NAND gates, the third NAND gate will generate the carry bit.

The correct answer is 1367.

• The equivalent octal number of 759 is 1367.

Key Points

• To convert decimal number 759 to the octal following are the steps:
  • Divide 759 by 8 keeping note of the quotient and the remainder.
  • Continue dividing the quotient by 8 until you get a quotient of zero.
  • Later, write out the remainders in the reverse order to get the octal equivalent of decimal number 759.
• 759 / 8 = 94 with remainder 7
• 94 / 8 = 11 with remainder 6
• 11 / 8 = 1 with remainder 3
• 1 / 8 = 0 with remainder 1
• Hence, the number is 1367.

• In an optical fiber, the information is passed through light, which must not escape outside of it.
• This phenomenon of confining the light inside the optical fiber is termed as Total internal reflection.
• For this, the construction and material used to ensure that the total internal reflection of light takes place to prevent the escape of it.

Principle:

• When light travels from a high refractive index medium to a low-refractive-index medium, it is refracted away from the normal as shown:

         

• At a certain angle θ_i, there is no refracted wave and the wave is totally internally reflected  (θ_r = 90°).
• This angle is called a critical angle.
• Inside an optical fiber, we have a high refractive index core (n₁) and low refractive index cladding (n₂).
• This results in the propagation of waves inside a fiber through total internal reflection phenomenon.

The communication satellite is in circular orbit and has orbital period same as that of the earth’s rotational period.

Concept:

For D flip-flop, the next state output (Q_n+1) from the present state input (Q_n) is given by:

Q_n+1 = D

Explanation:

Concept:

A function can be solved using K-map.

A four variable K-map has the following representation.

Observation:

f(A, B, C, D) = ∑(1, 3, 4, 6, 9, 11, 12, 14)

f = B D̅ + D B̅ 

So, Function f depends on only two variable and independent to other two variable.

Concept:

A transfer function is defined as the ratio of Laplace transform of the output to the Laplace transform of the input by assuming initial conditions are zero.

TF = L[output]/L[input]

For unit impulse input i.e. r(t) = δ(t)

⇒ R(s) = δ(s) = 1

Now transfer function = C(s)

Therefore, transfer function is also known as impulse response of the system.

Transfer function = L[IR]

IR = L^-1 [TF]

Calculation:

Given that r(t) = u(t), c(t) = t e^-t

Transfer function,

Explanation:

• PSK: It stands for phase shift keying.
• In PSK, binary 1 is represented with the actual carrier, and 0 is represented with the 180^o phase shift of carrier.
• 1 is represented as  s(t) = Accos(2πf_ct)
• 0 is represented as  s(t) = - Accos(2πf_ct)
• As in PSK, one bit is transmitted in a specific time constant.
• Similarly, in 16 PSK, log₂(16) = 4 bits are transmitted in a specific time constant which is known as 16-ary PSK.

B.W. of PSK = 2R_b

Whereas for M-ary PSK,

Hence M-ary is preferred due to less bandwidth.

• In 16 APSK, Amplitude and Phase both vary in a pattern as shown in the figure.
• 16 QAM is a signal in which two carriers shifted in phase by 90 degrees are modulated and combined. As a result of their 90° phase difference, they are in quadrature.
• Often one signal is called the In-phase or “I” signal, and the other is the quadrature or “Q” signal.

Hence the given figure is 16 QAM.

So the solution is option (2).

The correct answer is VRAM.

Key Points

• Video RAM, which refers to any random access memory (RAM), is a specialized form of DRAM.
• To provide high-speed serial streams of data to a video monitor, the VRAM design includes a series of registers called SAM registers, tied to a serial port.
• VRAM is specifically used to store image data for a computer display. Hence option 4 is correct.
• Video RAMs were first developed to provide continuous serial data streams for refreshing video screens.
• Each pixel or dot on a monitor requires one or more bytes of data that define the colour and to maintain a high-quality image on the screen, screen data must be refreshed on a fixed interval determined by the design of the monitor itself.

Additional Information

• Synchronous Graphics RAMs (or SGRAMs) are designed to address the high-speed, wide I/O requirements of this type of application.
  • These are used in graphics applications such as games, multimedia, frame buffers for 2D and 3D applications, and high-speed buffers for laser printers.
• DRAM stands for Dynamic Random Access Memory and is a technical term for a type of random access memory (RAM) that can retain its contents only for a very short time (say milliseconds).
  • So it must be continually refreshed by reading its contents at short intervals.

• The Fourier transform of a function is equal to its two-sided Laplace transform evaluated on the imaginary axis of the s-plane.
• The main drawback of Fourier transform (i.e. continuous F.T.) is that it can be defined only for stable systems, Whereas, Laplace Transform can be defined for both stable and unstable systems.
• An LTI system is stable if and only if the ROC of its system function H(s) includes the jω-axis [i.e., Re{s} = 0]  
• Fourier transform is defined only for stable signals. 
• From the given ROCs, B and C does not include the jω axis thus Fourier transform is not defined for B & C.

• The errors of instruments can be determined by a process known as calibration.
• Calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy.
• If the difference between the measured value and the pre-defined calibrated value are outside the acceptable range, then the instrument is said to be producing error in its measurement.

Additional Information

• Slip gauges or gauge blocks are used as standards for precision length measurement.
• A optical projector is an optical device which is used to enlarge the image.

S1: TCP handles both congestion and flow control          [Correct]

• TCP (Transmission control protocol) is a connection oriented reliable transport protocol. It provides process to process communications using port numbers.
•  It provides services like flow control, error control, congestion control. A packet that is sent is known as segment in TCP.
• In TCP, transmission requires three phases: connection establishment, data transfer and connection termination. It uses three way handshaking mechanism for connection establishment and termination.

S2: UDP handles congestion but not flow control       [incorrect]

• UDP (User datagram protocol) is called a connectionless, unreliable transport protocol.
• It does not add anything to the services of IP except providing process to process communication.
• There is no flow control, error control and congestion control mechanism in UDP. To send a message from one process to another,
• UDP protocol encapsulates and decapsulates messages in an IP datagram.

Concept:

The following figure shows the connection of buses between the microprocessor and memory

From the figure:

Address Bus:

An address bus is a bus that is used to specify a physical address. When a processor or DMA-enabled device needs to read or write to a memory location, it specifies that memory location on the address bus (the value to be read or written is sent on the data bus)

Data Bus:

It is a bi-directional bus.

Data and Instructions pass through this bus to reach the microprocessor.

This is responsible for the exchange of information between the main memory and microprocessor.

Control Bus:

This is a unidirectional bus.

This tells whether read or write, which operation should be performed that is in which direction the data should flow.

The correct answer is "option 2".

CONCEPT:

All the nodes are connected individually to the hub or switch in Star topology.

Star topology allows all the nodes in the same network to connect directly to a central device i.e. hub or switch.

Therefore, it is easy to connect new devices so that no other devices get disturbed while adding.

Also, it is easy to detect the fault in the node since nodes can be easily identified.

But star topology requires more cables than other topologies.

Hence, the correct answer is "option2".

Additional Information

Some other topologies are:

1. Bus topology

2. Mesh topology

3. Ring topology 

Answer: Option 4

Concept: 

word size= 

Data: 

Maximum addressable memory = 8 GB ≡ 233 Bytes 

Address bus width = 32 bit 

Explanation: 

Word size =  ≡ 2 B ≡ 16 bits

The correct answer is Persistent TCP connection, non-persistent TCP connection.

Key Points

• File Transfer Protocol or FTP is an application layer protocol and is used to communicate and transfer files between different systems on a TCP/IP protocol over the internet. It is a standard protocol for transmitting files from one host to another.
• It is also used for downloading files from servers to computers. Two computers can have different file conventions and different ways to represent data. This creates a problem while transferring.
• FTP overcomes these issues by establishing two connections between hosts. One is used for data transfer and the other connection is used for the control connection.
• For sending the actual file, the data connection is used. This connection is made between the data transfer process. For this non-persistent connection is used.
• Through control connection, we can send control information like user credentials, commands to change the remote directory, commands to retrieve and store files etc. For this FTP uses a persistent connection. Hence Option 2 is correct.

Additional Information

• FTP is one of the fastest and most efficient ways to transfer files from one computer to the other. The size limit of the file to be transferred is 2GB.
• Persistent connection or HTTP persistent connection is a communication channel that remains open for further HTTP requests and responses.
• Non-persistent connection is a channel that maintains no information about the previous requests.

The given sentence is of present perfect tense and it is in active form.

The structures for active/passive voices are:

Active: Subject + has/have + verb (IIIrd form) + object...

Passive: Object + has/have + been + verb (IIIrd form) + by + subject...

The active voice statement is in present perfect tense, thus the passive voice statement has to be in present perfect tense itself.

Out of the available options, only option (d) satisfies this criterion and thus, is the correct response.

Insolvent and bankrupt are often used interchangeably to refer to financial situations where an individual or entity is unable to meet financial obligations. They both imply a lack of ability to pay debts. So, in this case, "bankrupt" is a synonym for "insolvent."

Options (a) does not capture the essence of the phrase. Option (b) is true, but it is not the best explanation. "I was almost apart of it" indicates a sense of cohesiveness or felling at home. So,option (d) is correct.

The correct answer is "48".

Key Points

• MS Word is an example of a word processing software.
• In MS Word, Font size helps the user to write an essay, report or story in MS Word. The font option can be seen under the Home Tab, in MS Word.
• As per the image, it can be seen that the second largest font size that can be selected using the ‘Font Size’ drop-down list in MS Word 2016, is 48.

Thus the correct answer is 48.

Additional Information

• The leading creators of MS Word software are Charles Simonyi and Richard Brodie, launched in 1983 under Microsoft corporation.
• Microsoft word is recognised as a word processor software which means that a user can rewrite, erase or modify a document as per the requirement.
• The documents created in MS Word are very high in quality. MS Word is used for creating reports, stories, letters, resumes, etc. 
• It allows users to edit or modify the new or existing document with colour or any other formats like bold, italic and underline. 
• In MS Word, the users can write the stories in paragraph format.
• The file extension used in MS Word is .doc or .docx.

The correct option is (2)

Concept:-

Bytes:- Bytes are the best units of data on an external storage device.

Key Points

• A byte is an eight-binary digit long unit of data in the majority of computer systems. Most computers utilize bytes to represent characters like letters, numbers, and typographic symbols.
• Although they frequently offer instructions that can test and modify bits, computers are typically built to store data in units called bytes, which are multiples of bits.
• In a computer, the smallest unit of data is called a bit (short for binary digit). One of the binary values, 0, or 1, represents a bit.
• An external storage device, also known as auxiliary storage or secondary storage, is a container for all addressable data storage outside of the main storage or memory of a computer.
• Pen drives, CDs, and DVDs are a few examples of external storage devices. A pen drive is a tiny, independently powered device that attaches to a computer via a USB connector.​

To select all the boxes of an organization chart, you can follow any of the following methods:
Method A: Click Edit, Select All
- Click on the "Edit" option in the menu bar.
- Select the "Select All" option from the drop-down menu.
- This will select all the boxes in the organization chart.
Method B: Right-click the Chart Background, Click Select All
- Right-click on the background of the organization chart.
- From the context menu that appears, select the "Select All" option.
- This will select all the boxes in the organization chart.
Method C: Press and Hold the Shift Key and Click Each Box
- Press and hold the Shift key on your keyboard.
- Click on each box in the organization chart while still holding the Shift key.
- This will select each box one by one.
Method D: All of These
- All of the above methods (A, B, and C) can be used to select all the boxes in an organization chart.
Note: The specific method to select all the boxes in an organization chart may vary depending on the software or tool you are using to create the chart. The methods mentioned above are general approaches that are commonly used in various chart-making applications.

To find out what will happen when selecting Column G and H and choosing Insert → Columns, we need to understand the behavior of the Insert Columns function in Excel.
When selecting a range of cells and choosing to insert columns, the inserted columns will be added to the left of the selected range.
In this case, we are selecting Column G and H.
So, if we choose to insert columns, the following will happen:
- Two columns will be inserted after Column F because the selected range starts from Column G and H is the next column.
- Therefore, the correct answer is A: 2 Columns will be inserted after Column F.
Note: It's important to mention that the behavior may vary depending on the version of Excel or the settings applied. However, in most versions, this is the default behavior.

Long term scheduling
- Determines when new processes are admitted to the system
- Also known as admission scheduling or job scheduling
- Determines which processes should be brought into the system from the job pool or job queue
- Decides when a new process can be created and executed in the system
- Mainly focuses on managing the resources required by the processes and ensuring that the system does not become overloaded
Medium term scheduling
- Involves swapping processes between main memory and secondary memory (e.g., hard disk)
- Decides which processes should be swapped out of main memory and which should be brought back in
- It is responsible for managing the degree of multiprogramming or the number of processes in the ready state that are kept in main memory
Short term scheduling
- Also known as CPU scheduling
- Determines which process should be executed next by the CPU
- Determines the order in which ready processes are allocated the CPU for execution
- Focuses on improving the performance of the system by minimizing the waiting time and maximizing the CPU utilization
- Examples of short-term scheduling algorithms include First-Come, First-Served (FCFS), Round Robin, and Shortest Job Next (SJN)
None of these
- This option is incorrect as one of the above options is the correct answer

From Statement I: From this statement, we get the following table,

So, we get that 3 persons are born between L and G.

Clearly, data in statement I alone is sufficient to answer the question.

From Statement I: From this statement, we get the following table,

Clearly, data in statement II alone is not sufficient to answer the question as in both cases, two different answers are there. So we can't exactly say which case is correct as per statement II.

Hence, option A is the correct answer.

From the common explanation, we can say that R sits 3rd to the right of the one who sits immediate right of M. 
Hence, Option D is correct.
Final Arrangement:

Common Explanation:
References:
Only two boys sit to the left of J.
Eight boys sit between R and J.
Only three boys sit between R and M.
Inferences:
From the above references, we get two different cases:

References:
P sits fourth to the right of R.
O sits third to the left of M.
Inferences:
So, from this case 2 will be eliminated as P sits fourth to the right of R.

References:
Only three boys sit between O and H.
T sits third to the right of M.
V sits fourth to the right of O.
More than 12 boys sit between P and H.
More than seven boys sit between P and J.
Inferences:
From the above reference, we get the final arrangement:

The logic follows here : 
1. Sukhoi Su-30MKI is a Fighter Jet.
2. INS Vikrant is different from these two, it is an Aircraft Carrier.

The least possible Venn diagram for the given set of words is :

Hence, the correct answer is "Option (4)".

Additional Information

INS VIKRANT

• INS Vikrant is a 37,500-tonne carrier and has been launched almost four-and-a-half years after its keel was laid.
• The launch of warship, which has a length of 260 metres and is 60 metres wide.
• The launch has marked India's entry into a select club of countries capable of designing and building a carrier of this size and capability.
• There are 14 decks in all, including five in the superstructure. The ship has over 2,300 compartments, designed for a crew of around 1,700 people, including specialized cabins to accommodate women officers.
• There are 14 decks in all, including five in the superstructure. The ship has over 2,300 compartments, designed for a crew of around 1,700 people, including specialized cabins to accommodate women officers.

Sukhoi Su-30MKI

• The Sukhoi Su-30MKI is a twinjet multirole air superiority fighter developed by Russia's Sukhoi and built under license by India's Hindustan Aeronautics Limited (HAL) for the Indian Air Force (IAF). A variant of the Sukhoi Su-30, it is a heavy, all-weather, long-range fighter.
• The IAF has nearly 260 Su-30MKIs in inventory as of January 2020.
• Based on the Su-30 fighter aircraft, Su-30MKI is equipped with thrust vectoring control and canards.
• The aircraft has a length of 21.9m, wingspan of 14.7m and a height of 6.4m.
• The maximum take-off weight of Su-30MKI is 38,800kg.
• The Su-30MKI is also equipped with a N011M passive electronically scanned array radar, OLS-30 laser-optical locator system and Litening target designation pod to guide air-to-surface missile and laser guided munitions.
• The Su-30MKI is armed with a 30mm Gsh-30-1 cannon with 150 rounds of ammunition.
• The Su-30MKI fleet of IAF was fitted with air-launched version of BrahMos supersonic cruise missiles and was successfully tested in November 2017.
• The BrahMos can strike targets within the range of 290km.
• The IAF completed the successful integration of the cruise missile on the fighter, with the third live firing of the missile from the aircraft in December 2019.

As President is the nominal head of a country, similarly Governer is the nominal head of a State.