BEL Trainee Engineer Electrical Mock Test - 3 - Electrical Engineering (EE) MCQ

• Direct memory access (DMA) is a feature of computer systems that allows certain hardware subsystems to access main system memory (random-access memory), independent of the central processing unit (CPU).
• DMA avoids using the CPU thus allowing the CPU to attend another job
• It increases the speed of the data transfer between the memory and the I/O devices
• DMA is used when a large amount of data is to be printed out from the memory of a computer
• The problem of slow data transfer between input-output port and memory or between two memory is avoided by implementing the Direct Memory Access (DMA) technique
• It is implemented by using 8257 DMA controller

The power dissipated in the system due to corona discharges is called corona loss. Accurate estimation of corona loss is difficult because of its variable nature. It has been found that the corona loss under fair weather conditions is less than under foul weather conditions. The corona loss under appropriate weather conditions is given below by the Peek’s formula,

Where Pc – corona power loss

f – Frequency of supply in Hz

δ – Air density factor

En – r.m.s phase voltage in kV

Eo – disruptive critical voltage per phase in kV

r – Radius of the conductor in meters

D – Spacing between conductors in meters

From the above formula, we can observe that power loss due to corona is inversely proportional to the spacing between conductors.

Corona losses can be reduced by the following methods:

1) By increasing the conductor size (The voltage at which corona occurs can be raised by increasing conductor size. Hence, the corona effect may be reduced. This is one of the reasons that ACSR conductors which have a larger cross-sectional area are used in transmission lines.)

2) By increasing the distance between conductors

3) Using bundled conductors

4) Using corona rings

Concept:

KP = position error constant =

Kv = velocity error constant =

Ka = acceleration error constant =

Steady state error for different inputs is given by

From the above table, it is clear that for type – 1 system, a system shows zero steady-state error for step-input, finite steady-state error for Ramp-input and steady-state error for parabolic-input.

Calculation:

Velocity error coefficient,

Concept:

Synchronous speed N_s =120f/P

f = frequency in Hz

P = number of poles

Rotor speed N_r = N_s(1 - s) 

Where s = slip of the motor

Calculation:

Given, poles (P) = 6

Frequency (f) = 50 Hz

Slip (s) = 0.05

Speed of rotating field produced by rotor current is synchronous speed

Rotor speed rotates at speed slightly less than synchronous speed and it is given by
N_r = 1000(1 - 0.05) = 950 rpm

Speed of rotating field w. r.t. rotor = N_s - N_r = 50 rpm 

Concept:

Voltage across inductor is given by

(Power absorbing)

(Power delivering)

Nodal Analysis:

• Nodal Voltage Analysis uses the “Nodal” equations of Kirchhoff’s first law to find the voltage potentials around the circuit. So by adding together all these nodal voltages the net result will be equal to zero.
• If there are “n” nodes in the circuit there will be “n-1” independent nodal equations and these alone are sufficient to describe and hence solve the circuit.
• At each node point write down Kirchhoff’s first law equation(KCL), that is: “the currents entering a node are exactly equal in value to the currents leaving the node” then express each current in terms of the voltage across the branch using Ohm's law.
• So the nodal analysis is primarily based on the application of KCL and Ohm's law.
• For “n” nodes, one node will be used as the reference node and all the other voltages will be referenced or measured with respect to this common node

Calculation:

Circuit Diagram:

Given: L = 1 H, R₁ = R₂ = 1 Ω

By applying KCL,

I_L = eat + ebt

• A power MOSFET has three terminals called a drain, source and gate. It is a voltage-controlled device.
• As its operation depends upon the flow of majority carriers only, it is a unipolar device. Therefore, time delays caused by the removal or recombination of minority carriers are eliminated. Thus, it can work at high switching frequencies.
• These are so constructed as to avoid punch through
• The channel length is relatively small and the channel width is relatively large.
• These can be put in parallel to handle large currents

Punch through: It is observed when the depletion region on the source side of the body-drift p-n junction reaches the source region at drain voltages below the rated avalanche voltage of the device. This provides a current path between source and drain and causes a soft breakdown characteristic as shown.

The application of different two port network parameters are shown below.

Series compensation is the method of improving the system voltage by connecting a capacitor in series with the transmission line. In series compensation, reactive power is inserted in series with the transmission line for improving the impedance of the system. It improves the power transfer capability of the line. It is mostly used in extra and ultra-high voltage line. The following are the advantages of series capacitive compensation.

1. Increase in power transfer capability

2. Improvement in system stability

3. Load division among parallel line

4. Control of voltage

5. Lower the voltage drop

Important Points:

• Whenever an inductive load is connected to the transmission line, power factor lags because of lagging load current. To compensate this, a shunt capacitor is connected which draws current leading the source voltage. The power factor can be improved.
• Series capacitors are used to compensate for the inductance of the transmission line. They will increase the transmission capacity and the stability of the line. These are also used to share the load between parallel lines.
• Series reactors are used as current limiting reactors to increase the impedance of a system. They are also used to limit the starting currents of synchronous electric motors and to compensate reactive power in order to improve the transmission capacity of power lines.
• A shunt reactor is an absorber of reactive power, thus increasing the energy efficiency of the system.

Concept:

In AC bridges, there are two conditions to get bridge balance condition.

1. The magnitude of impedances satisfy the relationship, Z1Z4 = Z2Z3

2. The phase angles of impedances satisfy the relationship, ∠θ1 + ∠θ4 = ∠θ2 + ∠θ3

These two are independent conditions for balance and both of them must be satisfied for the bridge to be balanced.

Calculation:

From the given bridge, the condition to get balance is

Z₁ R₃ = R₂ Z₄

Concept:

The synchronous speed of a synchronous machine is given by

Where f is frequency and P is the number of poles.

A synchronous machine always rotates with a synchronous speed.

Calculation:

Alternator:

Number of poles (P_G) = P

Frequency (f_G) = 50 Hz

Synchronous speed,

Synchronous motor:

Let the number of poles is P_m

Frequency (f_G) = 60 Hz

Synchronous speed,

As the alternator is driven by the synchronous motor, both the machines operate at the same speed.

⇒ P_m = 1.2P

Creep:

• In energy meters, when the pressure coil is energized, a slow, but the continuous rotation of the disc is observed even when there is no current in the current coil. This is called Creeping.
• This can be due to several reasons such as overcompensation for friction, vibrations, stray field effects, and excessive pressure coil voltage.
• To prevent creeping, two diametrically opposite holes are drilled on the disc.
• The disc will stall when one of the holes comes under one of the poles of the shunt magnet. Thus the rotation is restricted to a maximum of half a revolution.

How to reduce creep:

• To prevent creeping, two diametrically opposite holes are drilled in the disc of energy meters.
• Due to this hole, the disc will come to rest when the hole comes under the edge of the pole of the shunt magnet. Thus creeping is limited to a maximum of half of the rotation

Concept:

Source transformation:

In the source transformation of a circuit, a voltage source can be transformed into the current source, and a current source can also be transformed into the voltage source.

According to source transformation technique, a voltage source-series resistance combination is equivalent to a current source-parallel resistance combination if and only if their

• Respective open-circuit voltages are equal
• Respective short-circuit currents are equal
• Resistance remains the same in both cases

The source transformation from one source to another source is as shown below.

1) Voltage source to current source:

2) Current source to voltage source:

Calculation:

Given circuit can be transformed as,

5 A, 5 Ω transform into 25 V in series with 5 Ω and 2 A, 4 Ω transform into 8 V in series with 4 Ω.

The circuit can be drawn as,

Now, V_eq = - 25 + (- 8) = - 33 V

R_eq = 24 V

We know that,

V = IR

Given, the signal

V (t) = 30 sin 100t + 10 cos 300 t + 6 sin (500t+π/4)

So, we have

ω₁ = 100 rads

ω₂ = 300 rads

ω₃ = 500 rads

∴ The respective time periods are

So, the fundamental time period of the signal is

as

∴ The fundamental frequency,

Concept:

For an ‘n’ flip flop counter,

• The total number of states = 2ⁿ (0 to 2ⁿ – 1)
• The largest number that can be stored in the counter = 2ⁿ – 1

To construct any mod counter, the minimum number flip flops required such that:

Modulus ≤ 2ⁿ

Where n is the number of counters.

Calculation:

Number no. of flip – flops are required to construct a mod-128 counter: 2ⁿ ≥ 128 i.e. n = 7

The literal meaning of bash is "strike hard and violently"
He was bashed on his head by street thugs
But the figurative meaning is "to hit someone by speaking or writing harshly about"
In the sentence above, bash refers to its figurative meaning
Hence the answer is C

Insinuate means suggest or hint (something bad) in an indirect and unpleasant way
Some insinuate that he doesn't love India enough to defend it wholeheartedly
It's degrading for people like Romney to insinuate that they don't contribute

Obdurate means obstinate or stubborn, hence compliant is the antonym.

The sentence "They will have completed the work by the time we get there" in the Active Voice can be transformed into the Passive Voice as:

A. The work will have been completed by the time we get there.

This option accurately represents the original sentence in the Passive Voice, maintaining its intended meaning.

The correct option is (4) By default, it has 3 placeholders.

Key Points

• Choose Home > New Slide to add a new slide to your presentation. The Title and Content slide layout are now added. This slide arrangement, which is the default, has placeholders for a title, bulleted text, pictures, and illustrations.
• Microsoft creates a Title slide by default when you create a new presentation because it expects the first slide in your presentation will be for the title. Two text placeholders are included on a title slide.
• The font family and font size of the regular input text are automatically carried over to the placeholder text, but there may be times when you want to modify the color of the placeholder text.

Additional Information

• Create a presentation storyboard or outline using the outline view. It merely shows the text on your slides; no graphics or other visual elements are displayed.
• Only a static string of text can be used as placeholder help information, which may not always be enough to convey the intended message.

The correct answer is .

Key Points

• In MS Word, Shift- Ctrl - K is used for small-cap in MS Word.
• Other few common keyboard shortcuts used in MS Word are given below:
  • In MS Word, Shift- Ctrl - > is used to increase the font size in the document.
  • In MS Word, Shift- Ctrl - D is used to double-underline the selected content.
  • In MS Word, Shift- Ctrl-A is used to open the list bullet.

Additional Information

• The leading creators of MS Word software are Charles Simonyi and Richard Brodie, launched in 1983 under Microsoft corporation.
• Microsoft word is recognised as a word processor software which means that a user can rewrite, erase or modify a document as per the requirement.
• The documents created in MS Word are very high in quality. MS Word creates reports, stories, letters, resumes etc. 
• It allows users to edit or modify the new or existing document with colour or any other formats like bold, italic and underline. 
• In MS Word, the users can write the stories in paragraph format.
• The file extension used in Ms Word is .doc or .docx.

The correct answer is Microsoft Outlook.

Key Points:

• Microsoft SQL Server is a relational database management system developed by Microsoft.
• MySQL Database Service is a fully managed database service to deploy cloud-native applications.
• Microsoft Outlook is the email service provided by Microsoft.
  • Hence this is the answer.
• Microsoft Access is the only application software you need to create apps, utilize databases, and store data in SQL Server and Microsoft Azure SQL.

The correct answer is Tab

Important Points

• Tab key should be pressed continuously while moving a column in MS Excel.
• Select the column that you want to move. Hold the Shift Key from your keyboard. Move your cursor to the edge of the selection.
• It would display the move icon (a four-directional arrow icon). Click on the edge (with the left mouse button) while still holding the shift key.
• Move it to the column where you want this row to be shifted.

Key Points

• Open a blank workbook on Excel and press the TAB key and your active cell should move to the column on the right. Hold in Shift and then press the TAB key and it reverses direction moving your active cell to the column on the left. You can also use this shortcut when tabbing through options in a dialogue box.
• Press the Enter key and your active cell should move to the row below. Hold in Shift and then press the Enter key and it reverses direction moving your active cell to the row above.
• 
• Using Shift and the arrow keys will select cells and using Shift when clicking on cells will select a contiguous cell range.

• The print option is available under the file menu or the office button option available at the left top corner of the screen in a document. Alternatively, you can go to the document that you wish to print and right-click ( using your mouse) it.
• All: The whole document will be printed.
• Current Page: Only the page where the cursor is currently located will be printed.
• Selection: Only the text highlighted on the screen will be printed. The printed copy of this text may well be wrapped differently from what is on screen.
• Print Page Number(s): Only the pages you specify will be printed. Specify pages by typing one or more page numbers as they appear on the pages of your document. You may specify a range of characters by using a hyphen. You may also specify one or more sets of pages by using a comma. For example, to print pages ix, x, 15, 16, and 17, you might type ix-x,15-17
• Page Sequence Number(s): Only the pages you specify will be printed, but you must specify those pages as if your document starts at page 1 and continues with pages 2, 3, etc. In other words, you may have to ignore the page numbers displayed on each page and simply count pages in the document or look at the status line when the cursor is on each page you wish to specify. This option is useful when one or more page numbers are repeated (e.g. you have two pages that are labeled "1"). You may use the hyphen and comma characters as described above.

The correct answer is OMR.

Important Points

• Optical mark recognition
  • It is the input device used to scan a marked answer book of a multiple choice question paper.
  • An optical answer sheet or bubble sheet is a special type of form used in multiple-choice question examinations. 
  • Optical mark recognition is used to detect answers.

Additional Information

• OCR
  • ​OCR (Optical Character Recognition) recognizes all the characters from the paper document.
  • It collects and stores them into an editable document.
• ​MICR
  • ​The term magnetic ink character recognition (MICR) refers to the line of numbers that appears at the bottom of a check.
  • The MICR line is a group of three numbers, which are the check number, account number, and bank routing number.
• Card reader
  • A card reader is a data input device that reads data from a card-shaped storage medium.

The correct answer is Home

Key Points

In Microsoft PowerPoint 2016, the Home tab in the ribbon contains a wide variety of tools and features, including commands related to paragraphs, drawing, and editing. This includes:

• Paragraph: The Home tab contains controls for paragraph alignment, bullets and numbering, indentation, and line spacing for text boxes in slides.
• Drawing: The 'Drawing' group in the Home tab allows you to add shapes, lines, and other drawing elements to your slides. It has tools for selecting, aligning, and distributing shapes, setting the order of elements, and more.
• Editing: The Home tab also contains the Clipboard group (for copy, paste, cut, and format painter features) and the Editing group (with find, replace and select functions).

These tools and features are helpful while creating and editing presentation content, making the Home tab a central location in PowerPoint for managing this content.

The correct answer is Ctrl + c, Ctrl + v.

Important Points

Ctrl + c is used to copy text and Ctrl + v is used to paste it.

Additional Information

Some other shortcuts-

•  Ctrl+Z- undo
•  Ctrl+X- Cut
•  Ctrl+F- Find
•  Ctrl+P- Print

As on melting, liquid is formed similarly on freezing solid is formed.

- Given Codes:
- PAINT = 74128
- EXCEL = 93596

- Analysis:
- Each letter is represented by a single digit in the code.

- Mapping:
- P -> 7
- A -> 4
- I -> 1
- N -> 2
- T -> 8

- Applying the same logic to ACCEPT:
- A -> 4
- C -> 5
- E -> 5
- P -> 7
- T -> 8

- So, the code for ACCEPT is 455978, which corresponds to option A.

As 24:60 = (2/5)

Similarly, (120/300) = (2/5)

1. Atheist: Someone who lacks belief in the existence of gods or deities and typically rejects organized religion.
   Religion: A system of beliefs, practices, and rituals centered around the worship of one or more gods or a divine power.
2. Sceptic: A person inclined to doubt or question accepted opinions and beliefs, especially those in religion or superstition.
   Pious: Devoutly religious or reverent, typically exhibiting strong religious devotion or dedication.
3. Iconoclast: A person who attacks or criticizes cherished beliefs or institutions, especially those in religion.
   Idol: An image or representation of a god used as an object of worship, or a person or thing that is greatly admired, loved, or revered.
4. Apostate: Someone who renounces or abandons a religious or political belief or principle, often after previously holding it.
   State: A politically organized community living under a government, usually sovereign, occupying a definite territory.

Both are pairs of antonyms.
Hence, Option A is correct.