BEL Trainee Engineer Electrical Mock Test - 1 - Electrical Engineering (EE) MCQ

Let F(ω) is the Fourier transform of f(t).

The closed-loop transfer function (CLTF) for unity feedback is given by:

Rearranging the above to get the Open Loop transfer function G(s), we get:

Putting s = 0, we get the DC gain as:

Applying KCL at V₊,

⇒ 5V₊ - 8 = V₀

From the fig. V₊ = V_in

⇒ 5V_in = V₀ + 8

Given V_sat = ±15 volts

So, for positive saturation, V₀ = +15 V

⇒ V₊ = V_in = 4.6 V

Now, for negative saturation, V₀ = -15 V

⇒ V₊ = V_in = -1.4 V

Concept:

The 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:

c(t) = 1 – e^-3t

Applying Laplace transform, i.e. time domain into s- domain

Input is unit step, i.e. r(t) = u(t)

In a DC motor, T ∝ ϕI_a

In series motor, ϕ ∝ I_a

⇒ T ∝ (I_a)²

In shunt motor, ϕ is constant

⇒ T ∝ I_a

The characteristic of DC series and shunt motor are shown below.

Characteristics of DC series motor:

Characteristics of DC shunt motor:

Concept:

In a parallel resonance circuit at the resonating frequency reactance will be ∞ and a combination of L & C will be open-circuited but however the LC combination work by exchanging their previously stored energy.

At the resonance:

I_L = -jQ₀I and,

I_C = +jQ₀I.

This is “current amplification”

‘Q₀’ indicates the quality factor, ‘I’ indicates the source current, ‘I_L‘ indicates the inductive current at the resonance and ‘I_C’ indicates the capacitive current at the resonance

Analysis:

The general parallel RLC circuit is mentioned below

The Laplace domain of the above parallel RLC circuit is

Finding resonance frequency (f_r)

Admittance (Y) calculation is easy in a parallel circuit and it is inversely proportional to the impedance

Comparing the equation (i) with Y = G ± jB_net we get

At the resonance, the imaginary part will be zero. So making 

After solving it,

We get  Radians/sec

Resonating frequency

Application:

For a parallel RLC circuit

When all components get doubled then-new resonant frequency (f₀') becomes,

The Measurement of Resistance according to classification is shown below:

Carbon:

• Carbon has approximate characteristics for resistance due to which carbon had been used in resistor construction for over a century.
• One of the main reasons is that resistors made out of carbon are regarded as highly reliable, that is, they don't fail often. They are also very effective at high energy levels.
• Carbon resistors can be found in two forms - carbon composition and carbon film.

Carbon composition resistors:

It contain both solid carbon (graphite) and a clay additive to help with durability and were formed with properly separated carbon black.

They are less common today due to their higher cost and lower reliability in high humidity applications.

• Because carbon resistors hold up well at high energy levels, they are often utilized in power supply applications.
• This includes both high voltage uses, like you would see being used by an electrical utility provider, and lower voltage applications, like a simple power strip-style surge protector or other home electronics.
  

Carbon film resistors:

• These are often used in devices involving x-rays and lasers and have some use with radar and welding technology as well.
• And chances are you probably have at least a few electronic devices in your home containing a carbon film resistor, perhaps even the surge protector your computer or cell phone is currently plugged in to.

Given that,

Measured value = 25.34 W

Absolute error = - 0.11 W

Absolute error = Measured value – true value

⇒ -0.11 = 25.34 – true value

Analog transducer: It converts the input signal into an output signal, which is a continuous function of time.

Ex: Thermistor, strain gauge, LVDT, thermocouple

Discrete transducer: It converts the input signal into the output signal, in the form of pulses i.e. it gives the discrete output.

Ex: Encoder, digital resolvers, digital tachometers, hall effect sensors, limit switches

Encoder:

It is a digital transducer which generates pulses corresponding to the angular rotation of the shaft.

They are further classified into two category

• Incremental encoder
• Absolute type optical encoder

Incremental encoder

It generates equally spaced pulses base on angular rotation of shaft

Absolute type optical encoder

sIt generates directly binary logic based on angular rotation of the shaft.

Concept:

The comparison of different feedback configuration is as follows:

Calculation:

Open loop gain (A) = 50

Input impedance (R_i)= 1 kΩ

Output impedance (R_o)= 0.5 kΩ

Negative Feedback factor (β) = 0.8

The amplifier is connected in current shunt configuration:

R_if = R_i / (1 + A) = 1000 / {1 + (50 × 0.8)} Ω = 24.39 Ω

R_of = R_o (1 + A) = 0.5{1 + (50 × 0.8)} kΩ = 20.5 kΩ

• When a thyristor or SCR is forward biased and is turned on by gate pulse, the conduction of anode current begins in the immediate neighbourhood of the gate cathode junction.
• Thereafter, the anode current spread over the entire gate cathode junction area.
• The thyristor or SCR is designed in such a way to permit the speared of current in the entire junction are as soon as possible.
• But in case, the rate of rise of anode current di/dt is more than the spread velocity of the current in the junction area, then there will a chance for the formation of local hot spot.
• Since the current rises in the vicinity of the gate to cathode junction, hot spot may be formed in that region.
• This hot spot formation is harmful for the SCR and may damage it
• Local spot heating is avoided by ensuring that the conduction spreads to the whole area very rapidly or the di/dt value must be maintained below a threshold (limiting) value.
• This is done by means of connecting an inductor in series with the thyristor.

Concept:

In a single-phase fully controlled rectifier, the average output voltage is given by

Where V_m­ is the maximum value of supply voltage

α is firing angle

Calculation:

At α = 0°, the average output voltage (V_o) = P volts

At α = 30°, the average output voltage will be

By using source transformation, the parallel combination of 2 A current source and 20 ohm resistance can be replaced by a series combination of 40 V voltage source with 20 ohm resistance

Now, the given circuit becomes

Now by applying KVL in the left most loop, we get

40 + 20 I + 10 + 30 (5 + I) = 0

50 I = – 200

⇒ I = – 4 A

Now Voltage across node ‘b’ can be calculated as

V_b = 30 (5 + I) = 30 (5 – 4)

V_b = 30 V

Registers in 8085 are primarily used to store temporary data.

General Purpose Registers:

• There are six 8-bit registers B, C, D, E, H, L. Each register contains 8 flip-flops hence, each register can store a maximum of 8 bit (1 Byte) of data.
• For storing data greater than 8 bits, these registers are used in pairs. There are three register pairs: BC pair, D – E pair, HL pair
• Each register pair can store a maximum of 16 bits of data (2 Byte).

Accumulator:

• It is an 8-bit register that contains 8 flip-flops. It can store a maximum of 8 bits of data.
• The importance of the accumulator is that, in most of the 8-bit arithmetic and logical operations, the microprocessor will always take the first 8-bit number from the accumulator.

Temporary Registers:

• There are three 8-bit registers W, X, and Z.
• Each register can store a maximum of 8 bits of data.
• These registers cannot be used or accessed by the programmer.
• These registers can be used only by the microprocessor for executing its operation i.e., the microprocessor will use these registers for the temporary storage of data.
• For storing 16-bit data W – Z pair can be used by the microprocessor.

The time required by the microprocessor to complete an operation of accessing memory or input/output devices is called Machine Cycle

The 4 steps involved in machine cycle in order are:

Fetch

decode

execute

store

In execution of any instruction first cycle is op-code fetch cycle.

After that depending upon the given instruction the memory read/write and I/O read/ write cycle occurs.

Concept:

For the negative feedback amplifier, the closed-loop gain is given by:

For the positive feedback amplifier, the closed-loop gain is given by:

Where A_OL is the open-loop gain

β is the gain of the feedback

Calculation:

The gain of feedback (β) = 0.009

Gain with feedback = 100

⇒ 0.9 A_OL + 100 = A_OL

⇒ A_OL = 1000

Gain without feedback or open-loop gain (A_OL) = 1000

Double Line to line Ground Fault (LLG):

• In double line-to-ground fault, the two lines come in contact with each other along with the ground.
• The probability of such types of faults is nearly 10%.
• All sequence networks are connected in parallel.

I_a0 + I_a1 + I_a2 = 0

V_a0 = V_a1 = V_a2

I_F = 3I_a0

Additional Information

The idiom crack someone up can be used to imply that you actually make someone laugh with something. It is regarding bringing a smile on the faces of people. Among the given options we can easily choose option D since it gives us the correct meaning of the phrase in underlined whereas the rest can be eliminated from consideration.

This makes option D the correct choice among the given options.

Engender is to cause or create.

The correct answer is the Presentation program.

Key Points

• Microsoft PowerPoint
  • It is a powerful slide show presentation program. Hence, Option 4 is correct.
  • It is a standard component of the company's Microsoft Office suite software and is bundled together with Word, Excel, and other office productivity tools.
  • The program uses slides to convey information rich in multimedia.

Additional Information

Domain Name:

• It resolves to the hostname of an IP address.
• It utilizes a hierarchical naming pattern and a distributed database of IP addresses and associated names.
• Domain names are symbolic strings associates with an IP address.
• Domain names are bifurcated into 2 main categories:- i) Generic top-level domains which represent the sponsored designated agencies, ii) ccTLD's (Country code top-level domains which represent the Nation designation.
• The top generic level domains currently in the world are:-

1. .aero - air transport industry
2. .asia - Asian Pacific region
3. .biz - business but all user
4. .cat - catan linguistic and cultural community
5. .com - commerce unit
6. .coop - cooperatives
7. .edu - Higher educational institutions
8. .gov - Government departments
9. .info - informational sites
10. .int - International organizations
11. .job - Employment related portals
12. .mil - US Military department
13. .mobi - Mobile users
14. .museum - Museaum/historical sites
15. .name - Individuals
16. .net - networks but unresttricted/all purpose
17. .org - organizations
18. .pro - Professional service providers
19. .tel - Online directory 
20. .travel - Travel industry

The full form of HTML is Hypertext Markup Language.

 Key Points

1.  HTML, in a full hypertext markup language, a formatting system for displaying material retrieved over the Internet.
2. Each retrieval unit is known as a Web page (from World Wide Web), and such pages frequently contain hypertext links that allow related pages to be retrieved.
3. HTML is the markup language for encoding Web pages.

Key Points
The To field is, according to the rules of email etiquette, meant for the main recipient(s) of your email. To be more precise, this field should be used to include the recipients who are required to take action in response to the email.

Hence the correct answer is To.

Additional Information
Cc stands for carbon copy which means that whose address appears after the Cc: header would receive a copy of the message.

• Bcc stands for blind carbon copy which is similar to that of Cc except that the Email address of the recipients specified in this field does not appear in the received message header and the recipients in the To or Cc fields will not know that a copy sent to these address.
• The subject line of an email is the single line of text people see when they receive your email. This one line of text can often determine whether an email is opened or sent straight to trash, so make sure it's optimized toward your audience.

The correct answer is DPI (dots per inch).

• The resolution of a printer is measured in DPI.

​Key Points

• The resolution of a printer 
  • In printing, the term Resolution refers to the sharpness and detail of images.
  • Higher resolution means more image detail.
  • Lower resolution means less image detail.
  • Common measures of resolution include
    • Pixels per inch (PPI).
    • Dots per inch (DPI).

Additional Information

• Difference PPI and DPI
• Dots per inch (DPI)
  • DPI refers to the number of printed dots contained within one inch of an image printed by a printer.
• Pixels per inch (PPI) ​
  • PPI refers to the number of pixels contained within one inch of an image displayed on a computer monitor.

The correct answer is the Visual Display Unit (VDU).

•  A Visual Display Unit (VDU) is also referred to as a Monitor and VDU (video display unit), a monitor is an output device that displays video images and text.
• A monitor is made up of circuitry, a screen, a power supply, buttons to adjust screen settings, and a casing that holds all of these components.
• Like most early TVs, the first computer monitors were comprised of a CRT (cathode ray tube) and a fluorescent screen.
• Today, all monitors are created using flat panel display technology, usually backlit with LEDs (light-emitting diode).

Important Point

• Soft copy output devices give screen displayed output that is lost when the computer is shut off.
• Once the soft copy is printed or burned, it is referred to as a hard copy.
• Audio Output is a type of soft copy.

Additional Information 

14 = (2 x 9 - 4)

26 = (2 x 15 - 4)

? = 15

Checking Statement I:

Using the above references, we get the information:
 
_ > _ > _ > _ > Tarak > _

Vijay > Komal > Rishi

Here, we cannot merge the above inferences to form a single arrangement of the order of heights of these persons.

So, we cannot say who among these persons is the tallest.

Hence, data in statement I alone is not sufficient.

Checking Statement II:

Using the above references, we get the information:

Rishi > Tarak/Sanjay

So, we cannot say who among these persons is the tallest.

Hence, data in statement II alone is not sufficient.

Checking Statements I and II:

Using the above reference, we get the following arrangement:

Usha > Vijay > Komal > Rishi > Tarak > Sanjay

Clearly, both statements I and II together are sufficient to answer the question.

Hence, Option D is correct.

From the common explanation, we get B sits second to the left of D.
Hence, Option D is correct.
Final Arrangement:

Common explanation:
References:
Six person A, B, C, D, E and F sit around a triangular table.
One person sits at each corner of the table facing away from the centre while one person sits at the middle of each edge facing toward the centre.
Inferences:
So, we need to arrange as follows to accommodate the information as stated in the question,

References:
Three persons sit between C and D, who is not facing the centre.
Inferences:
From the above reference, we get two different cases:
Case 1:

Case 2:

References:
F sits third to the left of C.
A sits second to the left of E.
A is not an immediate neighbour of D.
Inferences:
So, from this case 2 will be eliminated as A is not an immediate neighbour of D.
Case 1:

Case 2: (Eliminated)

Hence, Case 1 is the final arrangement.

As 'Indolence' and 'Work' are opposite to each other in the same way 'Taciturn' and 'speak' are opposite to each other.