BEL Trainee Engineer Electronics Mock Test - 2 - Electronics and Communication Engineering (ECE) MCQ

Process control system

An automatic control system in which the output is a variable is called a process control system.

An automatic control system is also known as a closed-loop system because the feedback will automatically correct the change in output due to disturbances.

An example of a basic process control system is a thermostat, a heating element, and a cooling element within a room. As the temperature in the room fluctuates beyond set boundaries, the thermostat turns on either the heating or cooling system to keep the room at a specific temperature.

EXPLANATION:

Faraday’s Law states that a change in magnetic flux induces an emf in a coil.

Also, Lenz’s Law states that this induced emf produces a flux which opposes the flux that generates this emf, i.e.

     ----(1)

EMF is also defined as:

Also, 

Putting the above in Equation (1), we get:

Additional Information

Maxwell's Equations for time-varying fields is as shown:

The correct answer is option 1):(Reversed biasing)

Concept:

Diode

A diode is a semiconductor device that essentially acts as a one-way switch for current.

It allows current to flow easily in one direction but severely restricts current from flowing in the opposite direction

The reverse bias of the diode

• When an external voltage (V ) is applied across the diode such that the n-side is positive and the p-side is negative, it is said to be reverse-biased.
• The applied voltage mostly drops across the depletion region. The direction of the applied voltage is the same as the direction of barrier potential.
• As a result, the barrier height increases, and the depletion region widens due to the change in the electric field.
• When a diode is given an external voltage that increases its potential barrier and restricts the flow of current.

Additional Information
Forward biased diode:

• In the forward bias, the p side of the diode is connected to the positive side of the battery and the n side is connected to the negative side of the battery.
• The direction of the applied voltage is opposite to the junction barrier potential. Therefore, the size of the depletion region decreases.

The data flow between the two devices can be in simplex, half duplex and full duplex modes.

Full Duplex

In Full duplex mode, both stations can transmit and receive at the same time.

Example: mobile phones

Important Points

Simplex

In Simplex, communication is unidirectional. Only one of the devices sends the data and the other one only receives the data.

Example: A CPU sends data while a monitor only receives data.

Half Duplex

In half duplex both the stations can transmit as well as receive but not at the

same time. When one device is sending other can only receive and vice-versa

Example: A walkie-talkie.

The correct answer is Magnetic Tape.

• Magnetic tape is a secondary storage device used for storing files of data; Example: a company’s payroll record.
• Access is sequential and consists of records that can be accessed one after another as the tape moves along a stationary read-write mechanism
• A hard disk is an electromechanical data storage device from which data is accessed in a random-access manner, individual blocks of data can be stored or retrieved in any order
• Both sequential and random access of data is possible in hard disk
• In random-access memory (RAM) the memory cells can be accessed for information transfer from any desired random location
• That is, the process of locating a word in memory is the same and requires an equal amount of time no matter where the cells are located physically in memory; Hence RAM is random access

In on-off control, thyristor switches connect the load to the AC source for a few cycles of input voltage and then disconnect it for another few cycles. It is also called burst firing, integral control.

 In phase angle control, thyristor switches connect the load to the AC source for some portion of each cycle of the input voltage.

The correct answer is 0.0.0.0 to 127.255.255.255

Key Points

• IP stands for Internet Protocol is a unique address that identifies a system or any device that works on the internet.
• It sets certain rules for transferring data over the internet.
• IPv4 consists of 32-bit integers that are expressed in decimal form, for example, 192.168.2.33. It is written as four 8-bit fields that are separated by a delimiter.
• Each 8-bit represents a byte of IPv4.
• An IP address is divided into a Network Address and a Host address.
  • The Network address is used to find the subnet in which the device is located whereas the Host address is used to find the device in the subnet.

​

• Public IPv4 address is classified into 5 classes A, B, C, D and E.
• The class A IPv4 range is 0.0.0.0 to 127.255.255.255. Hence option 3 is correct.

Additional Information

• Class B range is from 128.0.0.0 to 191.255.255.255.
• Class C range is from 192.0.0.0 to 223.255.255.255.
• Class D range is from 224.0.0.0 to 239.255.255.255.
• Class E range is from 240.0.0.0 to 255.255.255.254.

According to the maximum power transfer theorem, to obtain maximum power from a source with finite impedance, the impedance of the load must be equal to source impedance.

Derivation:

From the above circuit, the current flowing through the load, ‘I’ is given as

Power transferred to the load,

In the above equation, R_L is a variable, therefore the condition for maximum power delivered to the load is determined by differentiating load power with respect to the load resistance and equating it to zero.

⇒ (R_L + R_TH)² = 2R_L (R_TH + R_L)

⇒  R_L + R_TH = 2R_L

⇒ R_L = R_TH

The truth table for ALL options is shown

NAND

From the truth table, it is clear that in NAND gate output is low when all inputs are high

Important Points

OR

AND

NOR

The correct answer is All of the above.

Key Points

• The Internet is a huge collection of networks, a networking infrastructure. It encapsulates millions of computers together globally, forming a network in which any computer can communicate with any other computer as long as they are both connected to the Internet. In other words, it is a worldwide system of cross-connected computer networks, connecting millions of devices through which exchange of information such as data, news, and opinions, etc. is possible.
• It utilizes the TCP/IP (Transmission Control Protocol/Internet Protocol) to aid millions of users across the globe. So, TCP/IP can be called the backbone of the Internet. It is considered as a network of networks that consists of thousands of private and public, academic, business, and government interconnections. The Internet is often considered as “The Information Highway”, which implies that there is a straight and clear way of obtaining information. It connects thousands of computer networks. Each device connected to the Internet is known as the host and is independent. Through telephone wires, Fiber optical cable, and satellite links, Internet users can share a variety of information.
• The Internet is defined as an Information superHighway, to access information over the web. However, It can be defined in many ways as follows:
  • The Internet is a worldwide global system of interconnected computer networks.
  • The Internet uses the standard Internet Protocol (TCP/IP).
  • Each device connected to the internet is identified by its unique IP address.

The correct answer is option 4):(the same as that of Y)

Concept:

• The given circuit resembles the wheat stone bridge
• 
• The Wheatstone bridge works on the principle of null deflection, i.e. the ratio of their resistances is equal, and no current flows through the circuit. Under normal conditions, the bridge is in an unbalanced condition where current flows through the galvanometer. The bridge is said to be balanced when no current flows through the galvanometer.
• If the resistance of each resistor is 100 ohm, The bridge is at balance condition no current flows in the centre arm. the potential at X is equal to y

Option 4 is correct:

Definitions:

A memory that can retain the data even if the memory is not connected with the power supply is known as non-volatile memory.

A memory that loses data if the power supply is disconnected is called volatile memory.

Additional Information 

• The flash memory belongs to the non-volatile memory group as it can store data for a permanent time. Examples of flash memory are BIOS chips.
• ROM stands for read-only memory, and it is permanent storage where once the stored is stored then it cannot be updated or erased. An example of ROM is a controller chip used in electronic devices that defines its functioning.
• Hard Drive is a storage memory that is used as a secondary memory in computers. It stores data for a permanent time. But the data can be altered and erased as per the user requirement.

Inside a dynamic RAM chip, each memory cell holds one bit of information and is made up of two parts: a transistor and a capacitor.

Dynamic RAM memory cell is constructed using MOSFET and capacitor whereas Static RAM memory cell is constructed using 6 MOSFETs.

According to Thevenin’s theorem, any linear circuit across a load can be replaced by an equivalent circuit consisting of a voltage source V_th in series with a resistor R_th as shown:

Vth = Open circuit Voltage at a – b (by removing the load), i.e.

If a linear circuit contains dependent sources only, i.e., there is no independent source present in the network, then the open-circuit voltage or Thevenin voltage will simply be zero. (Since there is no excitation present)

Important Point

Various Theorem and the circuits where they are applicable is shown below in the table:

• The File Transfer Protocol (FTP) is a standard network protocol used for the transfer of computer files between a client and server on a computer network
• Simple Network Management Protocol (SNMP) is an Internet Standard protocol for collecting and organizing information about managed devices on IP networks and for modifying that information to change device behaviour
• The Simple Mail Transfer Protocol (SMTP) is a communication protocol for electronic mail transmission
• Radio Free Ethernet (RFE) is a network audio broadcasting system, It consists of programs and tools that allow packets of audio data to be transmitted around a network

Notes:

• FTP is Transport layer protocol
• SNMP, SMTP is an application layer protocol

The correct answer is option 2.

Key Points

• Serial Line Internet Protocol (SLIP) is a Data Link layer simple protocol that works with TCP/IP for communication over serial ports and routers. They provide communications between machines that were previously configured for direct communication with each other. 
• Border Gateway Protocol (BGP) is a Network layer used to exchange routing information for the internet and is the protocol used between ISP which are different ASes.
• User Datagram Protocol (UDP) is a Transport Layer protocol. UDP is a part of the Internet Protocol suite, referred to as UDP/IP suite. Unlike TCP, it is an unreliable and connectionless protocol.
• SNMP is an application layer protocol that uses UDP port number 161/162.SNMP is used to monitor the network, detect network faults and sometimes even used to configure remote devices

∴ Hence the correct answer is A-III, B -IV, C -II, D -I.

Additional Information

 

Meaning of brief: of short duration; not lasting for long.

Additional Information:

• Meaning of Limited: small or controlled in number, amount, etc.
• Meaning of Small: not large in size, number, amount, etc.
• Meaning of Little: not big; small

The passage is all about the movement of air.

Over dry land, the air becomes very hot & when the Sun goes down it cools off quickly

The correct answer is F11.

• The F11 key can take our screen into and out of full-screen mode quickly and easily. 

​Important Points

Function key

A function key is a key on a computer or terminal keyboard which can be programmed so as to cause an operating system command interpreter to perform certain actions, a form of a soft key.

​Key Points 

         F11​

• The Most simple use is the F11 key can take our screen into and out of full-screen mode quickly and easily. 
• F11 key can be used by combined with Shift, Ctrl, Alt keys.

Some of the uses of the F11 key in MS Word.

• SHIFT + F11 = Go to the previous field.
• CTRL + F11 = Lock a field.
• CTRL + SHIFT + F11 = Unlock a field.
• ALT + F11 = Display Microsoft Visual Basic Code.
• ALT + SHIFT + F11 = Display Microsoft Visual Studio Code.

​Additional Information

        F8

• ​​We can access the menu by turning on your computer and pressing the F8 key before Windows starts.

        F9

• F9 will refresh fields in Word and prompt Outlook to send and receive messages.

        F10

• ​F10 activates the menu bar or Ribbon of an open application.
• Shift + F10 is the same as right-clicking on a highlighted icon, file, or Internet link. 

The correct answer is option 4, i.e., They help you to club a group of commands and run them one after another

Additional Information

• A batch file is a text file that contains a sequence of commands for a computer operating system. It's called a batch file because it batches (bundles or packages) into a single file a set of commands that would otherwise have to be presented to the system interactively from a keyboard one at a time.
• Its extention is .bat.

The correct answer is Malware.

Key Points

• Malware, short for malicious software, is a blanket term for viruses, worms, trojans and other harmful computer programs hackers use to wreak destruction and gain access to sensitive information.
• Malicious Software refers to any malicious program that causes harm to a computer system or network. Malicious Malware Software attacks a computer or network in the form of viruses, worms, trojans, spyware, adware or rootkits.
• There are a number of different ways of categorizing malware:
  • A Worm is a standalone piece of malicious software that reproduces itself and spreads from computer to computer.
  • A Virus is a piece of computer code that inserts itself within the code of another standalone program, then forces that program to take malicious action and spread itself.
  • A trojan is a program that cannot reproduce itself but masquerades as something the user wants and tricks them into activating it so it can do its damage and spread.

An address of a website on the internet is called a URL.

Key Points

• URL stands for Uniform Resource Locator and is used to specify addresses on the World Wide Web.
• A URL is the fundamental network identification for any resource connected to the web (like images or sound files).

A URL has the following format:

Additional Information

1. Protocol:

• The protocol specifies how the information from the link is transferred. The protocol used for web resources is HyperText Transfer Protocol (HTTP).
• The protocol is followed by a colon, two slashes, and then the domain name
•  The domain name is the computer on which the resource is located.
• Links to particular files are specified after the domain name as shown above in the format.

2. Client:

• In computing, a client is a piece of computer hardware or software that accesses a service made available by a server as part of the client–server model of computer networks.

3. WAN:

• A wide area network (WAN) is a telecommunications network that extends over a large geographic area for the primary purpose of computer networking.

Setup Options in Page Setup Dialog Box:
The page setup dialog box allows users to customize various settings for printing a document. Here are the setup options that can be set in the page setup dialog box:
1. Orientation: Users can specify whether they want the document to be printed in portrait (vertical) or landscape (horizontal) orientation.
2. Margin settings: Users can adjust the margins of the document, controlling the amount of white space around the content.
3. Paper size: Users can select the size of the paper on which they want to print the document, such as A4, Letter, Legal, etc.
4. Headers and footers: Users can choose to include headers and footers on the printed document, which can contain page numbers, document titles, dates, and other information.
5. Scaling: Users can adjust the scaling of the document, allowing them to print the content at a smaller or larger size.
6. Print quality: Users can select the print quality, choosing between options like draft, normal, or high quality.
7. Page order: Users can specify the order in which the pages should be printed, such as from top to bottom or from left to right.
8. Row and column titles: Users can choose to repeat row and column titles on each printed page, ensuring that the headers are visible on every page.
However, there is one setup option that cannot be set in the page setup dialog box:
- Printer selection: The page setup dialog box does not provide an option to select a specific printer. Printer selection is usually done through the print dialog box, where users can choose the printer they want to use.
Therefore, option A: "Printer selection" cannot be set in the page setup dialog box.

In the question, We have to find the common to all three figures which is shown below-

Here, The highlighted area is common to all shapes.

Hence, Option (3) is correct.

From Statement 1:

We have, D moved a distance of 40m towards north.

From there he turns to the right and walked for 30m and reached school.

Here, we can’t determine in which direction is D’s home from the school.

From Statement 2:

We have, D is facing south. He turns right and walk for 100m.

After that he turned to the left walk for 50m and reach home.

Here, we can’t determine in which direction is D’s home from the school.

Hence option B is correct.

To solve the analogy problem where the pattern needs to be identified, let’s break it down step-by-step:

The analogy given is: 16 : 56 :: 32 : ?

We need to find the relationship between the numbers 16 and 56 and then apply that relationship to 32 to find the missing number.

1. Find the relationship between 16 and 56:

   • Step 1: Check the operations or patterns. Consider possible operations like addition, subtraction, multiplication, or division.

   • Step 2: Test if multiplication could be a pattern:

     16×3.5=56

     This works as:

     16×3.5=56

     Thus, multiplying by 3.5 seems to be the pattern.

2. Apply the same pattern to 32:

   32×3.5=112

   Therefore, according to this pattern, the number that replaces the question mark should be 112.

3. Verify the other options:

   • 96: This is much larger than expected.
   • 112: Also too large.
   • 121: Similarly, too large.
   • 128: While close, it’s not the result from our multiplication pattern.

Hence, the correct answer is:

112

In this figure counting the squares and we get the 27 squares.

From statement I alone, we don’t get the answer.

From statement II alone, Q is sitting 2nd to the left of T. T is facing P. The number of friends sitting between P and Q is same as the number of friends sitting between P and W.

From statement II alone, we don’t get the answer.

Combining both statement I and II, we get,

From statements I and II together, we don’t get the answer.

Hence, option ‘D’ is correct.