BEL Trainee Engineer Electrical Mock Test - 2 - Electrical Engineering (EE) MCQ

According to the question,

the Zener diode with a resistance ‘R_s’ across the supply ’30 V’ is given below.

Here given reference voltage is given as 10 V

∴ V_z = 10 V

Apply KVL in the first loop,

30 – I R_s – 10 = 0

Now when supply drops to 20 V from 30 V, then Zener current (I) will be:

∴ By applying KVL, we get

20 – IR_s – 10 = 0

IR_s = 10

Ohm’s law in the case of magnetic circuits can be stated as, the magnetic flux developed in the circuit is directly proportional to magnetomotive force. The relation is similar to Ohm’s law and can be formed by replacing electromotive force (emf) with mmf and electric current (i) with magnetic flux.

Flux = mmf/reluctance.

ϕ = mmf/S

Important Points:

Magnetic circuits are analogous to electric circuits. Some of the quantities are given below.

Hysteresis motor:

• A hysteresis motor is a synchronous motor with a uniform air gap and without DC excitation
• The torque in a hysteresis motor is produced due to hysteresis and eddy current induced in the rotor by the action of the rotating flux of the stator windings
• The hysteresis losses are very high. As the hysteresis losses are directly proportional to the area of the hysteresis loop, the hysteresis loop is very large.
• It has high starting torque as it has high rotor hysteresis loss
• It accelerates from rest to full-speed almost instantaneously
• It is not sensitive to fluctuations in supply voltage
• The noise level of the hysteresis motor is very low as compared to the induction motor because it operates at a constant speed and its rotor is smooth
• This type of motor is the smoothest running, quietest single-phase motor and is used for quality sound reproduction equipment like record players, tape recorders, etc.

• In a phase shift oscillator, the frequency-determining elements are R and C

Important Point:

• RC phase shift oscillator as shown in the figure is used to invert the input for 180° phase difference.
• The single R-C network gives the 60° phase shift
• In RC phase shift oscillator the inverting amplifier produces 180° phase shift.
• The RC Phase shift Oscillator: has a fixed frequency and is used at lower frequencies

dv/dt protection:

• When the SCR is forward biased, junctions J1 and J3 are forward biased and junction J2 is reverse biased. This reverse biased junction J2 exhibits the characteristics of a capacitor.
• If the rate of forward voltage applied is very high across the SCR, charging current flows through the junction J2 is high. This current is enough to turn ON the SCR even without any gate signal.
• This is called as dv/dt triggering of the SCR. This can be reduced by using RC snubber network across the SCR.
• A snubber circuit consists of a series combination of resistance Rs and capacitance Cs in parallel with the thyristor.
• False turn – ON of an SCR by large dv/dt, even without application of gate signal can be prevented by using a snubber circuit.

Concept:

• SF6 gas has excellent insulating property and it has a high electronegativity.
• Due to high electronegativity, the recovery of dielectric strength after the arc interruption in the SF6 circuit breaker is very fast.
• It has a high affinity for absorbing free electrons.
• It absorbs electrons from a negative ion. The attachment of electron with SF6 molecules may occur in two different reactions.
• Ions are obviously much heavier than a free electron and the overall mobility of charged particles in SF6 gas is much less compared to the other common gases.

Advantages of SF6 Circuit Breaker:

• High dielectric strength
• Take minimum time in installation
• The gas is non-inflammable and chemically stable; The decomposition products are non-explosive
• It gives noiseless operation it does not make a sound like an air-blast circuit breaker during operation
• Minimum maintenance
• The same gas is re-circulated into the circuit thereby reducing the requirement of SF6 gas.

Disadvantages of SF6 Circuit Breaker:

• The SF₆ gas is identified as a greenhouse gas, safety regulation is being introduced in many countries in order to prevent its release into the atmosphere.
• Puffer type design of SF₆ CB needs high mechanical energy which is almost five times greater than that of the oil circuit breaker.

Concept:

In transformer voltage regulation is given by,

Voltage regulation = x (Rpu cosθ ± Xpu sinθ)

Where x = fraction of load

Rpu = resistance in pu (we can use % resistive drop in fraction)

Xpu = reactance in pu (we can use % reactive drop in fraction)

+ for lagging load

– for leading load

Calculation:

When transformer is working at 0.8 lagging power factor at full load

⇒ cos θ = 0.8, sin θ = 0.6

x = 1

Rpu = 1%

Xpu = 4%

%V.R. = 1 × (1 × 0.8 + 4 × 0.6) = 3.2%

When transformer is working at 0.8 leading power factor at full load

⇒ cos θ = 0.8, sin θ = 0.6

x = 1

Rpu = 1%

Xpu = 4%

%V.R. = 1 × (1 × 0.8 - 4 × 0.6) = -1.6%

Current source inverter:

• In current source inverter, the input current remains constant due to large inductance, but this input current is adjustable.
• The current source inverter is also called the current fed inverter.
• The output voltage of the inverter is independent of the load.
• The magnitude and nature of the load current depend on the nature of load impedance.
• It is most suitable for supplying power to capacitive loads.

Advantages:

• The circuit for CSI is simple as it uses only converter grade thyristor which should have the reverse blocking capability, and also able to withstand high voltage spikes during commutation.
• An output short circuit or simultaneous conduction in an inverter arm is controlled by the ‘controlled current source’ used here, i.e., a current-limited voltage source in series with a large inductance.
• The commutation failure in the same leg does not occur due to the presence of a large inductance and has the capability to recover from occasional commutation failure.
• The converter-inverter combined configuration has inherent four-quadrant operation capability without any extra power component.

Disadvantages:

• A minimum load at the output is required, and the commutation capability is dependent upon load current. This limits the operating frequency and also puts a limitation on its use for UPS systems.
• At light loads, and high frequency, these inverters have sluggish performance and stability problems.

• Param Yuva 2 is a supercomputer developed by India.
• Supercomputer Param Yuva-2 was rated first in India, 9th in the Asia Pacific Region and 44th in the world among the most Power-efficient computer system as per the Green 500 list. The list was released in June' 2013 at the International Supercomputing Conference held at Leipzig, Germany.
• It was developed by the Centre for Development of Advanced Computing (C-DAC).
• It uses hybrid technology, processor, co-processor and hardware accelerators.

https://www.cdac.in/index.aspx?id=hpc_nsf_param_yuva_ii

For parallel connection of single phase transformers, primary windings of the transformers are connected to source bus-bars and secondary windings are connected to the load bus-bars.

Various conditions that must be fulfilled for the successful parallel operation of single phase transformers:

1. Same voltage ratio & turns ratio (both primary and secondary voltage rating is same).

2. Same percentage impedance and X/R ratio.

3. Identical position of tap changer.

4. Same phase angle shift (vector group are same).

5. Same frequency rating.

6. Same polarity.

7. Same phase sequence.

Some of these conditions are convenient and some are mandatory.

The convenient are: Same voltage ratio & turns ratio, same percentage impedance, same KVA rating, same position of tap changer.

The mandatory conditions are: same phase angle shift, same polarity, same phase sequence and same frequency.

When the convenient conditions are not met paralleled operation is possible but not optimal.

• A potentiometer is an instrument designed to measure an unknown voltage by comparing it with the known voltage.
• The known voltage may be supplied by a standard cell or any other known voltage reference source
• It makes use of a balance or null condition, no current flows and hence no power loss is consumed in the circuit
• Thus, the determination of voltage by a potentiometer is quite independent of the source resistance
• Measurements using comparison methods are capable of a high degree of accuracy because the result obtained does not depend upon the actual deflection of the pointer, as in the case of deflection methods
• Hence potentiometer is the best device to measure the true open circuit e.m.f. of a battery

• DC excitation in a synchronous machine is provided to the rotor poles so that a rotating field is produced when the rotor moves.
• Loss of excitation results in asynchronous operation with the machine working as an induction generator.
• Offset Mho relay is an inherently directional relay.
• Due to the directional nature of Mho relay, it can detect easily the loss of excitation of an alternator.

The center of offset mho relay can be shifted to any point in the R – X plane by characterizing the relay as

If | Z – Z_s | < |="" />_set|, relay trips CB

If |Z – Z_s| > | Z_set|, relay Blocks CB

Operating characteristics of offset Mho relay are shown below.

Microprocessor 8085 can perform following types of arithmetic operations:

1. Addition
2. Subtraction
3. Increment
4. Decrement

8085 Cannot perform:

1. Multiplication
2. Division

There are instructions to perform addition, subtraction but not division and multiplication in 8085.

Concept:

The current in each parallel path = I/A

A is the number of parallel paths

In a wave wound generator, number of parallel paths = 2

In a lap wound generator, number of parallel paths = number of poles

Calculation:

Power (P) = 25 kW

Voltage (V) = 200 V

Total current

Number of parallel paths = 2

The current in each parallel path = 125/2 = 62.5 A

Let us first learn the meanings of the given words:
Enhancement (noun): an increase or improvement in quality, value, or extent.
Modified (adjective): revised or changed.
Amendments (noun): a minor change or addition designed to improve a text, piece of legislation, etc.
Since the context is that the changes are in the bill, noun ‘amendments’ is the perfect fit contextually and grammatically.

Hence, the correct answer is option D.

One word substitution is Oligarchy.

Monarchy: A form of government with a monarch at the head.

Oligarchy: A small group of people having control of a country or organization.

Plutocracy: A state or society governed by the wealthy.

Autocracy: A system of government by one person with absolute power.

We can say that ,
Use structure “auxiliary + past participle”
The above given sentence is given in Passive Voice :-
Wine should be opened about three hours before it is used.
Hence ,required answer will be option D .

The given sentence in active voice is: "Ads on TV increase the sale of any commodity."

The correct transformation of this sentence into the passive voice is: "The sale of any commodity is increased by ads on TV."

Therefore, the correct answer is option B: "The sale of any commodity is increased by ads on TV."

The correct answer is 4.4.

Key Points

• The formula to calculate the average of given numbers is equal to the sum of all the values divided by the total number of values.
• In MS-Excel the format of using the Average formula is
  • ​= Average(number1, number 2, number 3, .....).
• Here, the sum of numbers is 22 and this should be divided by 5.
• Hence the result is 4.4

Additional Information

• SUM(): This function is used to adds all the values within a cell range.
• ROUND(): The round function is used to round a number to a specified number of digits.
• RAND(): This function is used to returns a random number greater than or equal to 0 and less than 1.
• MOD(): This function is used to find the remainder after dividing a number by another number.

The correct answer is Datasheet.

Key Points

• Datasheet
  • Each table that appears as a spreadsheet grid is called a datasheet. Hence, Option 2 is correct.
  • A datasheet is a useful way of viewing data in Access.
  • A database is a collection of tables.
  • Most importantly, datasheet view allows a user to view many table records at the same time.
  • In datasheet view, information is displayed in rows and columns—similar to a spreadsheet.
  • Records are displayed as rows, so each row is an individual record.
  • Within each row, columns represent fields within the record.
  • At the top of the datasheet, a window is the title bar, the Quick Access toolbar, and the Ribbon.
  • The bottom of the window has a status bar and on the right side of the window is a scroll bar as you would expect.
  • Many of the features that are common to spreadsheets are present in Access datasheet windows.
  • A user can modify row height, column width, font size to change the amount of data that fits without scrolling.
  • A user can also change the order of the rows or columns displayed in the window.
  • Datasheet views are a common display tool for tables, queries, and forms in Access.
  • There are some irregularities in the functionality of the datasheet windows for these depending on the underlying data sources.

Image of Datasheet View:

Additional Information

• Query
  • A query is like a saved filter. It enables us to combine data into a single datasheet from multiple tables.
• Record
  • A record is a row in a table that consists of information about something.
• Table
  • A spreadsheet table, in OpenGL Tablets, is an analog of the Excel table with rows, columns, formulas, and calculations as contents.
  • Spreadsheets can also call decision tables or other executable tables to make decisions on values, and based on those, make calculations.

The correct answer is Fire fox.

Key Points

• An Operating System
  •   It is software that acts as an interface between computer hardware components and the user.
  • Every computer system must have at least one operating system to run other programs. Applications like Browsers, MS Office, Notepad Games, etc., need some environment to run and perform their tasks.

• The OS helps you to communicate with the computer without knowing how to speak the computer's language. The user can't use any computer or mobile device without having an operating system.   

Additional Information

• Symbian
  • It is a discontinued mobile operating system and computing platform designed for smartphones.
  • Symbian was originally developed as a proprietary software OS for PDAs in 1998 by the Symbian Ltd. consortium.
• Android
  • It is a mobile operating system based on a modified version of the Linux kernel and other open-source software, designed primarily for touchscreen mobile devices such as smartphones and tablets.
• Firefox
  • It is a Browser also known as Mozilla Firefox or simply Firefox is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation.
  • Firefox uses the Gecko layout engine to render web pages, which implements current and anticipated web standards.
• iOS 
  • This is the world's most advanced mobile operating system.

The Correct answer is Home Page.

Key Points

• A home page also refers to the first page that appears upon opening a web browser, sometimes called the start page, although the home page of a website can be used as a start page.
• A home page on a website serves as a launching pad to other products and services.

Additional Information

• An identification page printed at the beginning of a print job by many print spoolers. It serves as a title page and separator between print jobs.
• The Banner page is the first page of a print job used as a separator of print jobs and used to identify the originator of the print job request.
• A Master Page is a nonprinting page that you can use as the template for the rest of the pages in your document.
• Master pages can contain text and graphic elements that will appear on all pages of a publication (i.e. headers, footers, page numbers, etc.).

The correct answer is Adobe Inc.

• Photoshop is a software program used extensively for image editing, graphic design, and digital art. Thus Adobe Inc company have the right to sell this software.
• Adobe Photoshop is a raster graphics editor developed and published by Adobe Inc. for Windows and macOS.
• It was originally created in 1988 by Thomas and John Knoll. Since then, the software has become the industry standard not only in raster graphics editing but in digital art as a whole.
• Photoshop can edit and compose raster images in multiple layers and supports masks, alpha compositing, and several color models including RGB, CMYK, CIELAB, spot color, and duotone.

Key Points

• Photoshop uses its own PSD and PSB file formats to support these features.
• Photoshop's naming scheme was initially based on version numbers. However, in October 2002, each new version of Photoshop was designated with CS plus a number.
• Photoshop was developed in 1987 by two brothers Thomas and John Knoll, who sold the distribution license to Adobe Systems Incorporated in 1988.
• Photoshop 1.0 was released on February 19, 1990, for Macintosh exclusively.
• On March 31, 1995, Adobe purchased the rights for Photoshop from Thomas and John Knoll for $34.5 million.

Additional Information

The correct answer is option 1 i.e Root Directory.

Key Points

• The root directory is the top-level directory of a file system.
  • The root directory contains all other folders in the drive or folder.
  • The default root directory in Windows is C:\.

Additional Information

• A database is a data structure that store organised information electronically in a computer system 
  • Microsoft Access is an application used for database purposes.
• A cell is the intersection of row and column.

From the common explanation, we get Sagar scored 2nd lowest marks.

Hence, Option D is correct.

References:

Tarun scored more marks than Priyam but less than Rahul.

Sagar neither scored 3rd highest nor scored lowest marks.

Priyam scored more marks than Anurag.

Sagar scored less than Tarun, who scored 87 marks.

Inferences:

From the above references, we get the following arrangements

Rahul > Tarun (87) > Priyam > Sagar > Anurag

These are all defensive games.

As 'smoke' leads to 'pollution' in the same way ''War'' leads to 'destruction'.

From Statement I:

From this statement, we get the following ranking.

Person in the row = 8 persons + Akansha + 4 persons + Rhea + 7 persons + Harshita + 8 persons

So, we get that Rhea is 17th from the bottom in the class.

Clearly, Statement I alone is sufficient to answer the question.

From Statement II:

From this statement, we get the following ranking.

Person in the row = 11 persons + Yamini + 13 persons + Rhea + 4 persons

So, we get that Rhea is 5th from the bottom in the class.

Clearly, Statement II alone is sufficient to answer the question.

Clearly, Either Statement I or Statement II alone is sufficient to answer the question.

Hence, option C is the correct answer.

Peel : Peal

The above words represent pair of homophones.

(c) is a pair of homophones. (a), (b) and (d) do not have pairs of homophones.

Hence, correct option is C.

From the common explanation, we get D sits fifth to the right of N.

Hence, Option D is correct.

Final Arrangement:

Common Explanation:

References:

J sits fourth to the right of O and N sits second to the left of J.

Only H sits between J and G.

Inferences:

From the above references, we get

References:

Only D sits between G and C

G is not an immediate neighbour of J but fifth to the right of I.

M, who sits exactly in the middle, is second to the right of I.

Five persons sit between L and J.

Inferences:

From the above references, we get

References:

E is not an immediate neighbour of N.

Inferences:

From the above reference, we get the final arrangement: