BEL Trainee Engineer Electronics Mock Test - 1 - Electronics and Communication Engineering (ECE) MCQ

In a spread-spectrum system, the process gain (or "processing gain") is the ratio of the spread bandwidth to the unspread (or baseband) bandwidth. It is usually expressed in decibels (dB).

Using quadrature receiver gives twice as gain as single channel receiver i.e 3 dB.

The correct answer is option 4.

Classification of Electrical drive

1.)  On the basis of the operation

• Continuous duty drives
• Short-time duty drives
• Intermittent duty drives

2.) On the basis of control

• Manual
• Semi-automatic
• Automatic

3.) On the basis of machine connection

• Individual drive
• Group drive
• Multi motor drive

4.) On the basis of dynamics and transients

• Variable position control
• Step speed control Reversible and non - reversible
• Uncontrolled constant speed reversible and non - reversible

The correct answer is option 2.

Concept:

Minimum header size of IPv4 = 20-byte

The maximum header size of IPv4 = 60 bytes

The header length field in the IPv4 header is 4 bits.

Maximum possible value (1111) = 15.

Explanation:

The given data,  the first 8 bits is 0100 0010,
The First 4 bits represent version IPV4 (0100).
And another 4 bits represent header length ( bits decimal value x 4) which should range between 20 to 60 bytes. This means that these 4 bits must represent the decimal number between 5 and 15. 

Which is 2 × 4 = 8 bytes which is not possible since the minimum header length for IPv4 is 20 bytes. 

Here (0010=2)

Here are the last bits of decimal value=2.
Hence Receiver will reject the packet.

Hence the correct answer is The receiver rejects the packet.

Drift Current:

• Drift current in the diode is the combined effect of movement of the minority charge carrier and majority charge carriers and also on the electric field applied to the diode.
• Drift current is due to the motion of charge carriers when a force exerted on them by an electric field.
• In the p-n junction diode, electrons are the majority charge carriers in the n-region and holes are the majority charge carriers in the p-region.
• When an electric field is applied to the diode there is more number of covalent bonds break and the concentration of charge carriers also increases in both region (p-type, n-type), and hence they affect the drift current in the diode.

Drift current I_drift = J_drift × A

Where, J_drift = Drift current density

A = Area of semiconductor

Now, J_drift = σ ⋅ E

= (nqμ_n + p.qμ_p)

σ = Conductivity

E = Electric field

⇒ I_dr = (nq.μ_n + p.qμ_p) ⋅ E A,

n = Number of electrons in n region

p = Number of holes in p-region

q = Charge on electrons and holes

μ_p = Mobility of holes

μ_n = Mobility of electrons

Additional Information

Diffusion

1) Diffusion is a natural phenomenon.

2) The migration of charge carriers from higher concentration to lower concentration or from higher density to lower density is called diffusion.

3) Diffusion is mainly due to the concentration gradient and is always negative.

It is given by:

 for holes and

 for electrons.

Diffusion current is calculated by:

 -----(1)

where,

D_p is hole diffusion constant in cm²/sec

and q is charge in Coulomb.

Given:

Binary number = 11001

Calculation:

According to the question, we have

Converting the binary number to decimal number

⇒ Decimal number = 1 x 24 + 1 x 23 + 0 x 22 + 0 x 21 + 1 x 20

⇒ 16 + 8 + 0 + 0 + 1

⇒ 25

∴ 25 is the decimal equivalent of the binary number (11001)2

1) Shift registers are sequential circuits that are used for storage or for the transfer of binary data.

2) The shift register takes the data present on the input and "shifts" it to the output once every clock cycle.

3) Every shift in the register content to the right by one-bit position is equivalent to dividing the original number by two 

4) Every shift in the register content to the left by one-bit position is equivalent to multiplying the original number by two.

This is explained with the help of the following Example:

Example:

Let the original content of a 4-bit right shift register is 0100 which is 4 in decimal, i.e.

(0100)2 = (4)10 

1). Shifting the content of the register to the left by two-bit position, the new content now becomes (10000)2, which is 16 in decimal, i.e.

(10000)2 = (16)10

Clearly, the original number is multiplied by 4. 

2). Shifting the content of the register to the right by one-bit position, the new content now becomes (0010)2, which is 2 in decimal, i.e.

(0010)2 = (2)10

Clearly, the original number is divided by 2. 

Concept:

Adaptive Delta Modulation (ADM):

• This Modulation is the refined form of delta modulation.
• This method was introduced to solve the granular noise and slope overload error caused during Delta modulation.
• In DM the step size is constant and depends on a maximum slope but in ADM the step size is varied according to the slope of the message signal.

Key Points

• In Adaptive Delta Modulation, the step size of the staircase signal is not fixed and changes depending upon the input signal.
• Here first the difference between the present sample value and previous approximation is calculated.
• This error is quantized i.e. if the present sample is smaller than the previous approximation, quantized value is high or else it is low. (This is performed by the comparator)
• The output of the one-bit quantizer is given to the Logic step size control circuit where the step size is decided.

The electric field at a distance 'r' due to a point charge is given by:

r = distance from the point charge

â_r = unit direction vector

This is explained with the help of the following diagram:

As the distance from the point charge decreases the magnitude also decreases.

Important Points:

• The direction is radial: outward for +|Q| and inward for -|Q|
• Magnitude: Constant on any spherical shell
• Flux through any shell enclosing Q is the same: E_AA_A = E_BA_B

Concept:

Resolution is given by:

 ----- (1)

Where;

Vfs = Full-scale voltage or maximum voltage

If the reference voltage is given, then:

 ------ (2)

Application:

Given that,

Vref = 10 V

Number of bits (n) = 8

From equation (2);

Resolution 

Now, from equation (1);

V_fs = Resolution × (2ⁿ - 1)

Vfs = 9.961 V

Channel capacity, 

but, for a noisy channel

∴ C ≈ B.W log₂1

≈ 0 bps

The probability of error, 

P_e = 0.75 = 3/4

∴ The entropy for a noisy channel is:

= 

= 0.311 + 0.5 = 0.811

Concept:

The total number of complex multiplies for an N-point FFT is given by:

Calculation:

Given N = 32

So, for a 32-point FFT, the total number of complex multiplies required will be: 

  = 16 × 5 = 80

An energy meter is a type of integrating instrument.

Types of measuring instruments

The measuring instruments are divided into four major parts:

1.) Indicating Instrument

• The indicating Instrument displays only the value of the electrical quantities per time of measurement.
• This instrument gives the reading only when connected to the electrical supply. Otherwise, it goes to the zero position.
• Ammeters, Voltmeters, Wattmeters, etc are examples of indicating instruments.

2.) Recording Instrument

• The recording Instrument displays and records the reading of the electrical quantities per time of measurement.
• This instrument is generally used in the generating Station and substation.
• ECG and X-Rays are examples of recording instruments.

3.) Integrating Instrument

• The Integrating Instrument displays, record, and add the numerical value of the reading of the electrical quantities per time of measurement.
• The energy meter and Ampere-hour meter are examples of integrating instruments.

4.) Null Deflection Instrument

• The Null Deflection Instrument shows the reading of the electrical quantities without the deflection angle at per time of measurement.
• The potentiometer is an example of a null deflection instrument.

The correct answer is the Stack pointer.

Key Points

• The system's computer organisation defines how the units in the system are structured, arranged and interconnected.
• The significant components of Computer organization are ALU, CPU, memory and memory organization and it deals with low-level design issues.
• A  stack is a memory unit with an address register called stack pointer (SP) and follows the Last In First Out (LIFO) method.
  • It is the most important feature of the CPU. It saves data such that the element stored last is retrieved first.
• The stack pointer always indicates the stack's top element, which means which location the data has to be inserted. Hence option 2 is correct.
• It can insert an element into or delete an element from the stack. The insertion operation is the push operation and the deletion operation is the pop operation.

Additional Information

• There are two types of stack available: Memory stack and Register stack.
  • In the memory stack, the stack depth is flexible. It occupies a large amount of memory data.
  • The register stack is also a memory device present in the memory unit, but it handles only a small amount of data because the size of the register stack is very small compared to the memory.
• Device controllers are software modules that are plugged into the operating system to handle a particular device or an I/O device.

Electrostatic type instrument:

• The electrostatic type instrument uses a static electrical field to produce the deflecting torque.
• These types of instruments are generally used for the measurement of high voltages.

Important Points

The principle of working of all electrical measuring instruments depends upon various effects of electric current or voltage as shown in the table given below.

As we can say that ,
Tangible means available physically, concretely, elusive is something that eludes, i.e, is difficult to catch, touch or understand, palpable is a synonym to tangible.
Hence , Elusive is antonym word of Tangible . 

The correct answer is ​A.L.U.

Key Points

• An arithmetic logic unit(ALU) is a major component of the central processing unit of the computer system.
• It does all processes related to arithmetic and logic operations that need to be done on instruction words. Hence option 3 is correct.
• ALU is also known as an Integer Unit (IU). The arithmetic logic unit is that part of the CPU that handles all the calculations the CPU may need.
• In some microprocessor architectures, the ALU is divided into the arithmetic unit (AU) and the logic unit (LU).
• The function of ALU.
  • logical operations.
  • Bit-Shifting Operations.
  • Arithmetic operations.

Additional Information

• Cache memory
  • It is also called Cache, a supplementary memory system that temporarily stores frequently used instructions and data for quicker processing by the central processor of a computer. The cache augments and is an extension of, a computer's main memory. 
• Random Access Memory (RAM) 
  • It is used to store the programs and data being used by the CPU in real-time. The data on the random access memory can be read, written, and erased any number of times. RAM is a hardware element where the data being currently used is stored. It is a volatile memory.
• Read-Only Memory (ROM) 
  • It is a type of memory where the data has been prerecorded. Data stored in ROM is retained even after the computer is turned off ie, non-volatile.

Recycle bin:

• The Recycle Bin acts as a 'holding bay' for deleted items, such as files and folders (and even shortcuts!).
• When someone deletes a file or folder, it is not deleted from the computer permanently. Instead, Windows 7 places the deleted items into the Recycle Bin.
• The Recycle Bin is a folder located on the Windows desktop. When it is empty, the icon is an empty recycle bin. If it contains one or more items, the icon changes to a recycle bin with papers in it.

Hence, the Recycle bin is A folder on the desktop.

The correct answer is option 3.

Key Points

•  The logic unit of ALU is responsible for performing logical operations such as AND, OR, NOT, and XOR.
• It receives input from the memory unit and sends the output to the register.
• The arithmetic unit of ALU is responsible for performing arithmetic operations such as addition, subtraction, multiplication, and division.
• The comparing unit of ALU is responsible for comparing two values and determining if they are equal, greater than, or less than each other.

Additional Information

•  Comparing unit: The comparing unit is responsible for comparing two values and determining if they are equal, greater than, or less than each other.
• Arithmetic unit: The arithmetic unit is responsible for performing arithmetic operations such as addition, subtraction, multiplication, and division.
• Number unit: The number unit is not a component of ALU and is an incorrect option.

The correct answer is They used small number of transistors that emitted less amount of heat.

Key Points

• They used small number of transistors that emitted less amount of heat, this statement about first-generation computers is false.
  • The generations of computers are characterized by a major technological development that fundamentally changed the way computers operate.
  • It results in the development of smaller, cheaper, more powerful, and more efficient and reliable devices.

Additional Information 

• First Generation Computers (1940-1956)
  • The first computers used vacuum tubes for circuitry and magnetic drums for memory.
  • These were enormous in size, taking up entire rooms.
  • These computers were very expensive to operate.
  • In addition to using a great deal of electricity, the first computers generated a lot of heat, which was often the cause of malfunctions.
  • First-generation computers relied on machine language, the lowest-level programming language understood by computers to perform operations.
  • They could only solve one problem at a time.
  • It would take operators days or even weeks to set up a new problem and calculate.
  • However, they were the fastest-calculating device of their time.  
  • The input was based on punched cards and paper tape, and the output was displayed on printouts.
  • The UNIVAC and ENIAC computers are examples of first-generation computing devices.
  • The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951.​

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.

Each computer connected to the internet must have a unique IP address.

Here is a detailed explanation:

1. What is an IP address?

• An IP (Internet Protocol) address is a unique numerical identifier assigned to each device connected to a computer network.


• It serves as a way to identify and communicate with devices over the internet.


• IP addresses are divided into two types: IPv4 (32-bit) and IPv6 (128-bit).

2. Importance of unique IP address:

• Each computer on the internet must have a unique IP address to establish a connection and communicate with other devices.


• Without a unique IP address, there would be conflicts and confusion in routing data between devices.


• IP addresses allow for the proper delivery of data packets across the internet.

3. Obtaining a unique IP address:

• Internet Service Providers (ISPs) assign IP addresses to their customers.


• Dynamic IP addresses are assigned temporarily and can change over time.


• Static IP addresses are permanent and do not change.


• Devices can also use Network Address Translation (NAT) to share a single IP address among multiple devices within a local network.

4. IP address format:

• IPv4 addresses are written as four sets of numbers separated by periods (e.g., 192.168.0.1).


• IPv6 addresses are written as eight groups of four hexadecimal digits separated by colons (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334).

5. Role of routers:

• Routers play a crucial role in connecting devices to the internet.


• They assign unique IP addresses to devices within a local network and handle the routing of data packets to the appropriate destinations.

In conclusion, each computer connected to the internet requires a unique IP address to establish proper communication and data transfer. This unique identifier ensures that data packets are correctly routed between devices and allows for efficient connectivity across the internet.

The network topology with bi-directional links between each possible node is called a Mesh topology.
Explanation:
In a Mesh topology, each node in the network is connected to every other node through individual bi-directional links. This means that there is a direct connection between each pair of nodes in the network.
Here are some key points about Mesh topology:
- Full Mesh: In a full mesh topology, each node has a direct connection with every other node in the network. This provides high redundancy and fault tolerance but requires a large number of physical connections.
- Partial Mesh: In a partial mesh topology, only some nodes have direct connections with other nodes. This reduces the number of physical connections required but still provides some redundancy and fault tolerance.
- Advantages: Mesh topology offers several advantages, including:
- High fault tolerance: If one link or node fails, there are alternative paths for communication.
- High scalability: It is easy to add or remove nodes without affecting the rest of the network.
- High security: Each node has its own dedicated connection, making it difficult for unauthorized access.
- High performance: Mesh topology allows for parallel and simultaneous data transmission between nodes.
- Disadvantages: However, there are also some disadvantages to using a Mesh topology:
- High cost: The implementation of numerous physical connections can be expensive.
- Complex management: With a large number of connections, managing and troubleshooting the network can be challenging.
- High redundancy: In a full mesh topology, there may be redundant connections that are not regularly utilized.
In conclusion, a Mesh topology provides a highly interconnected network where each node has a direct link to every other node in the network, allowing for efficient communication and high fault tolerance.

The pattern followed is:

Hence, the correct answer is "127".

Alternate Method
The pattern followed is:
3 = 2² - 1
7 = 2³ - 1
15 = 2⁴ - 1
31 = 2⁵ - 1
63 = 2⁶ - 1
127 = 2⁷ - 1
Hence, the correct answer is "127".

1st term = 34/2 +1 = 18
2nd term = 18/2 +1 = 10
3rd term = 10/2 +1 = 6
4th term = 6/2 + 1  = 4

Thus, the missing number is 5th term = 4/2 + 1 = 3

The logic followed is:

Abduct and Kidnap are synonyms.

Similarly,

Fierce and Violent are synonyms.

Hence, the correct answer is "Violent".

Preparing the family tree using the following symbols:

On decoding L θ Z β T means L is the mother of Z and Z is the sister of T.

i) L is mother of T → True
ii) L is father of T → False (as L is mother of T) 
iii) T is father of L → False (as T is either son or daughter of L)
iv) Z is daughter of T → False (as Z is sister of T)
Hence, 'L is mother of T' is the correct answer.

There are 8 triangles in the figure. By counting the individual triangles, we can see that there are 2 large triangles, 4 medium triangles, and 2 small triangles, making a total of 8 triangles.

Following the common explanation, we get “Y sits near A”.
Hence, option C is correct.
Final Arrangement:

Common Explanation:
References:
1. Two people are sitting between A and Z.
2. C sits fourth to the right of Z.
3. The number of people sitting to the right of A is the same as the number of people sitting to the left of Z.
4. The number of people sitting between A and C is the same as the number of people sitting between X and C.
5. X is an immediate neighbour of D, who sits on one of the ends.
6. The number of people sitting between D and C is the same as the number of people sitting between C and Y.
7. At most 25 people are sitting in a row.
Inferences:
From reference 1, we get two possible cases.
From reference 7, case2 was eliminated.
Hence, Case 1 is the final arrangement.

Triangle, square and rhombus are shapes. Tangent is not.

As Silence is opposite to noise, similarly Baldness is opposite to Hair.