BEL Trainee Engineer Electronics Mock Test - 3 - Electronics and Communication Engineering (ECE) MCQ

Controlling can be defined as that function of management that helps to seek planned results from the subordinates, managers, and at all levels of an organization. The controlling function helps in measuring the progress towards the organizational goals & brings any deviations, & indicates corrective action.

Key Points

Limitations of Controlling:

1. Difficulty in setting quantitative standards:

• Control system loses its effectiveness when the standard of performance cannot be defined in quantitative terms and it is very difficult to set the quantitative standard for human behavior, efficiency level, job satisfaction, employee’s morale, etc.
• In such cases, judgment depends upon the discretion of the manager.

2. No control on external factors:

• An enterprise cannot control external factors due to its variation and causes such as government policy, technological changes, change in fashion, change in competitor’s policy, etc.

3. Resistance from employees:

• Employees often resist control and as result effectiveness of control reduces.
• Employees feel control reduces or curtails their freedom.
• Employees may resist and go against the use of cameras, to observe them minutely.

4. Costly affair:

• Control is an expensive process it involves a lot of time and effort as sufficient attention has to be paid to observe the performance of the employees.
• To install an expensive control system organizations have to spend a large amount.
• Management must compare the benefits of controlling systems with the cost involved in installing them.
• The benefits must be more than the cost involved then only controlling will be effective otherwise it will lead to inefficiency.

Therefore, option 4 is the correct answer.

Concept:

Bitrate in the TDM system is given as:

R_b = bits per frame × frame rate

Units:

Calculation:

Given in a TDM system bitrate R_b = 32 kbps

Each slot has 16 bits i.e., each frame has 16 bits

The frame rate will be:

Frame rate = 2000 fps

Concept:

SSB (Single Side Band) modulation is a technique that allows only one sideband to pass saving bandwidth and power both. 

Practically it is very difficult to pass only a single sideband.

Analysis:

Ex: If we consider a single-tone modulating signal as x(t) = cos ω_mt, the SSB modulated wave with only the upper sideband will be represented as:

cos ((ω_c + ω_m)t) = cos ω_c.cos ω_mt – sin ω_c.sin ω_mt

and with lower sideband only will be represented as:

cos (ω_c - ω_m)t = cos ω_ct .cos ω_mt + sin ω_ct. sin ω_mt

where sin ω_mt is the Hilbert transform of the original message signal x(t) = cos ω_mt

Generalizing this for any signal m(t), we can say that the SSB modulated signal with only upper sideband will be:

m(t) cos ω_ct – m̂(t) sin ω_ct, (option 1 is the correct answer)

Similarly, we can say that the SSB modulated signal with only lower sideband will be:

m(t) cos ω_ct + m̂(t) sin ω_ct,

where m̂(t) is the Hilbert transform of m(t).

SSB/SC is generated using a balanced modulator circuit as shown:

X-Y recorder:

• X-Y recorders is type of graphic recorders.
• An XY recorder plots the instantaneous relation between two variables.
• The X-Y recorders records the variation in one dependent variable with respect to an independent variable.
• In X-Y recorders, an EMF is plotted as a function of another EMF.
• This is done by having one self-balancing potentiometer control the position of the rolls while another self- balancing potentiometer controls the position of the recording pen.

Noise power is given as:

Pn = KTB

Where,

K = Boltz man's constant

T = temperature

B = Bandwidth over which noise is measured

When the bandwidth is increased, then system becomes fast as it reduces rise time, increases stability as well as reduces oscillations in the response but according to the above equation, the noise also increases.

Concept:

In a 4 × 1 MUX

Truth-Table

MUX contains AND gate followed by OR gate

Calculation:

By re-drawing the circuit diagram

∴ I₀ = 1, I₁ = 0, I₂ = 0, I₃ = 0 & (x= S₂, y = S₁)

Now output of 4 × 1 MUX is

Y = F = S̅₁ S̅₂ I₀ + S̅₁ S₂ I₁ + S₁ S̅₂ I₂ + S₁ S₂ I₃

F = x̅ y̅ 1 + x̅ y 0 + x y̅ 0 + x y 0

Norton's Theorem :

Any linear bilateral network consisting of multiple resistances and sources can be replaced by a resistor R_N in parallel of Current source I_N .

Calculation:

R_N : 

Disable all independent sources and find equivalent resistance.

R_N = ( 20 || 10 ) + 20 = 26.6 ohm

I_N :

Short circuited current

Let node voltage of 10 ohm is V

Apply nodal analysis

V = 2.5V

I_N = V /20 = 125 mA

The transport layer can be either connectionless or connection oriented. A connectionless transport layer treats each segment as an independent packet and delivers it to the transport layer at the destination machine. A connection oriented transport layer makes a connection with the transport layer at the destination machine first before delivering the packets. After all the data are transferred, the connection is terminated.

A low earth orbit satellite can provide large signal strength at the earth station because path loss is low since low earth orbit (LEO) is the nearest orbit to the earth so path loss is minimum.

Free space path loss 

Where R is the distance between stations as we can see.

Free path loss ∝ (distance)²

As (distance ↑) → (Pathloss ↑) (R_x signal strength ↓)   

• Complementary Metal-oxide-semiconductor (CMOS) uses complementary & symmetrical pair of P-type & n-type MOSFETS.

• The two important characteristics of CMOS devices are high noise immunity and low power dissipation.
• CMOS devices dissipate less power than NMOS devices because the CMOS dissipates power only when switching (“dynamic power), whereas N channel MOSFET dissipates power whenever the transistor is on because there is a current path from Vdd to Vss.
• In a CMOS, only one MOSFET is switched on at a time. Thus, there is no path from voltage source to ground so that a current can flow. Current flows in a MOSFET only during switching.
• Thus, compared to N-channel MOSFET has the advantage of lower drain current from the power supply, thereby causing less power dissipation.

HTTP: Multiple TCP connections can be used at client and server end.

FTP: For FTP also multiple connections can be used at the same time.

TELENT: Only one TCP connection is allowed at a time.

SMTP: SMTP also allows only one TCP connection at a time.

Digital to Analog Modulation technique is shown.

As shown QAM is the mixture of ASK and PSK.

Hence, amplitude and the phase of the carrier frequency both vary with the message signal.

Constellation diagram of a QAM signal with 2 different amplitude levels and 8 different phases is shown.

Being a single wavelength light source with uniform phase:

• Laser light travels smoothly with very little dispersion.
• Makes it ideal for long-distance communication.
• For fiber optics with glass fibers, light in the infrared region is widely used which has wavelengths longer than visible light, typically of 850, 1300, and 1550 nm.
• Transmitters (Lasers or LEDs) emit in infrared regions and are used as a light source for fiber transmission.
• The laser acts as the best source in optical communication because it is a single wavelength light source.
• Ordinary light contains many different wavelengths of light, differences emerge in the speed of the transmission, reducing the number of signals that can be transmitted in any set time.
• Receivers (photodetectors) at these particular wavelengths are also easy to construct.

Notes:

• We use infrared because the attenuation of the fiber is much less at those wavelengths.
• The attenuation of glass optical fiber is caused by two factors, absorption, and scattering.
• Absorption occurs in several specific wavelengths called water bands due to the absorption by minute amounts of water vapor in the glass.

The correct answer is Wireless communication between devices.

Key Points

Bluetooth technology

• Bluetooth is a Wireless Personal Area Network (WPAN) technology and is used for exchanging data over smaller distances.
• Bluetooth technology allows devices to communicate with each other without cables or wires. Bluetooth relies on short-range radio frequency, and any device that incorporates the technology can communicate as long as it is within the required distance.
• Bluetooth is used for short-range communications between device peers, as well as a device to the peripheral. The number and variety of peripherals that communicate via Bluetooth are immense—wireless headsets for hands-free cell phone use, keyboards, mice, videogame controllers, audio speakers, you name it.

The radar principle is used in the detection of aircraft.

Radar:

• Radar is an acronym for Radio Detection and Ranging. 
• The term "radio" refers to the use of electromagnetic waves with wavelengths in the so-called radio wave portion of the spectrum, which covers a wide range from 104 km to 1 cm.  
• It is basically an electromagnetic system used to detect the location and distance of an object from the point where the RADAR is placed.
• It works by radiating energy into space and monitoring the echo or reflected signal from the objects.
• It works on radio frequency in the range of about 3 kHz to 300 GHz.
• But most of the RADAR operates between 220 MHz to 35 GHz.

Radar systems have been used in military applications for

• Ground surveillance 
• Missile control, fire control,
• Air traffic control (ATC),
• Moving target indication (MTI),
• Weapons location
• Vehicle search

Scattering:

• Scattering is the loss of signal caused by the diffusion of a light beam, where the diffusion itself is caused by microscopic variations in the transmission medium
• Scattering typically happens when a light signal hits an impurity in the fibre

Dispersion:

• Dispersion is defined as pulse spreading in an optical fibre
• As a pulse of light propagates through a fibre, elements such as numerical aperture, core diameter, refractive index profile, wavelength, and laser linewidth cause the pulse to broaden

Attenuation:

• The attenuation of an optical fibre measures the amount of light lost between input and output
• Total attenuation is the sum of all losses
• For a given fibre, these losses are wavelength-dependent

Inter-symbol Interference:

• This is the effect of dispersion on optical fibre
• Intersymbol interference occurs when the pulse spreading caused by dispersion causes the output pulses of a system to overlap

We require secondary memory for our computer systems as:

1. Limited capacity of main memory - Although we can add main memory to a system but it is extremely difficult for general users. And we also want to store all our programs and data inside the main memory. But main memory having limited capacity, can accommodate only a limited amount of data and small number of programs.
2. Main memory is expensive - Main memory is faster than secondary memory and hence, it is highly expensive. Therefore, we can have multiple secondary storages in the cost of a single main memory.
3. Main memory possesses highly volatility - Main memory is volatile storage whereas secondary memory is non-volatile storage, that is, main memory will lose its content as soon as its power is turned off whereas secondary memory will retain the content even when the power is lost.

All these reasons makes us to use secondary memory along with main memory.

The given circuit is redrawn as:

Applying KVL around the loop, we get:

100 - 8I - 40 - 30I - 2I = 0

60 = 40 I

I = 1.5 A

Now, the voltage across the 30 Ω resistor will be:

V_30Ω = 1.5 × 30 

V_30Ω  = 45 V

Safe means free from harm. Its opposite is insecure.

As we can say that ,
Nebulous is indistinct something that does not have a clear outline, Concrete is solid and of definite shape.
Hence , Concrete is antonym ( opposite ) of Nebulous . 

The government got troubled because it lacks the independence of talking decisions. Because democracy does't allow to do so.

The government went ahead when it didn't get the support of BJP and the left.

The correct answer is "4".
Key Points

• In MS Word, four types of alignments are used for aligning the paragraph. These are left, right, centre and justify.
• Left alignment: In this structure, the paragraph is aligned towards the left to the ruler of the MS Word document. The keyboard shortcut used for left alignment is Ctrl + L.
• Right alignment: In this structure, the paragraph is aligned towards the right to the ruler of the MS Word document. The keyboard shortcut used for right alignment is Ctrl + R.
• Centre alignment: In this structure, the paragraph is aligned in the middle of the MS Word document. The keyboard shortcut used for left alignment is Ctrl + E.
• Justify alignment: In this structure, justify alignment option keeps each paragraph line at an equal distance from the left and right page margins in the MS Word document. The keyboard shortcut used for left alignment is Ctrl +J.

Thus the correct answer is 4.
Additional Information

• The page margin defines an area in MS Word where text, and graphics can be added. It acts as a border to the page of MS Word.
• The paragraph margin defines the area for the paragraph.
• Page orientation is used for displaying the working area of MS Word. There are two types of page orientation. These are portrait and landscape.
  • Portrait: It will hold the page vertically.
  • Landscape: It will hold the page horizontally.
• The leading creators of MS Word software are Charles Simonyi and Richard Brodie, launched in 1983 under Microsoft corporation.

User-level threads are very effective because a mode switch is not required to switch from one thread to another. Here is a detailed explanation:

• Definition: User-level threads are managed by the application without the intervention of the operating system. They are created and scheduled by the application itself.


• Advantages: User-level threads offer several advantages, including:




• No mode switch: User-level threads do not require a mode switch from user mode to kernel mode when switching between threads. This makes the context switch faster and more efficient.


• Thread management control: The application has full control over thread management, including scheduling, synchronization, and resource allocation.


• Portability: User-level threads can be easily ported across different operating systems, as they are independent of the underlying kernel.




• Disadvantages: User-level threads also have some limitations:




• Blocking system calls: If a user-level thread performs a blocking system call, it will block the entire process, as the kernel is unaware of the individual threads.


• Limited parallelism: User-level threads may not fully utilize the available hardware resources, as the operating system schedules threads at the process level rather than at the thread level.

In conclusion, user-level threads are very effective because they eliminate the need for a mode switch and provide greater control over thread management. However, they also have some limitations that need to be considered in certain scenarios.

Internet safety is a crucial aspect that applies to everyone who uses a computer that can connect to the Internet, regardless of their online activities. It is essential to understand the potential risks and take necessary precautions to protect oneself and their personal information. Here are the key points to consider:

1. Online Identity Protection:

• Creating strong and unique passwords for all online accounts


• Using two-factor authentication when available


• Avoiding sharing personal information on public platforms


• Being cautious while interacting with strangers online

2. Phishing and Scams:

• Avoiding clicking on suspicious links or downloading attachments from unknown sources


• Verifying the legitimacy of websites before providing personal or financial information


• Being skeptical of offers that seem too good to be true


• Regularly updating and using antivirus software

3. Cyberbullying and Online Harassment:

• Being mindful of one's online behavior and treating others with respect


• Blocking and reporting any instances of cyberbullying or harassment


• Keeping personal information private and not engaging in online conflicts

4. Social Media Safety:

• Reviewing and adjusting privacy settings regularly


• Being cautious while accepting friend requests or following strangers


• Avoiding sharing sensitive or personal information publicly


• Using discretion while posting photos or videos

5. Safe Online Shopping:

• Verifying the credibility of online sellers and websites


• Using secure payment methods and checking for secure website connections (https)


• Keeping track of online transactions and reviewing bank statements regularly

6. Protecting Personal Data:

• Regularly backing up important files and data


• Using encryption tools to secure sensitive information


• Avoiding downloading files or software from untrusted sources

7. Safe Internet Usage for Children:

• Setting up parental controls and monitoring online activities


• Teaching children about online dangers and responsible Internet use


• Encouraging open communication and reporting any uncomfortable situations

The above information can be summarized below diagram,

Therefore, the code for “was” will be “3”. 

Hence, option 4 is the correct answer.

1) GRASS – FEARLESS (Cannot be formed because G is missing)

2) RESEAL – FEARLESS (Can be formed)

3) LESSER – FEARLESS (Can be formed)

4) ERASE – FEARLESS (Can be formed)

Hence, the correct answer is “GRASS”.

According to the sequence in the dictionary: 

The correct order of the given words is:

2. Arrange

1. Arrest

3. Arrogant

4. Arrow

Hence, the correct answer is "2, 1, 3, 4".

Additional Information

1. First of all, check the common letter in all.

2. Arrange them according to the alphabet they come first. 

3. When common letters are arranged, then go for the rest.