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Past Questions
A major disadvantage of solar power is ___
A)
its cost effectiveness compared to other types of power
B)
its efficiency level compared to other types of power
C)
the variation in sunshine around the world
D)
lack of knowledge on long-term economic impacts
The correct answer is **c: the variation in sunshine around the world**. Solar power depends directly on sunlight, so its availability is uneven across regions and also varies with weather, season, and time of day. This makes it a major practical disadvantage.
Why the others are incorrect:
- **a: its cost effectiveness compared to other types of power** — This is not generally a disadvantage; solar power has become increasingly cost-effective in many places.
- **b: its efficiency level compared to other types of power** — Solar panels do have moderate efficiency, but this is not the most standard or major disadvantage compared with the variability of sunlight.
- **d: lack of knowledge on long-term economic impacts** — This is not a direct technical disadvantage of solar power; it is more of an uncertainty in policy or economic analysis.
For minimum weight of the transformer, the iron weight should be __ the weight of the copper:
A)
More than
B)
Equal to
C)
Less than
D)
None of these
For a transformer of minimum weight, the iron weight should be less than the copper weight. This follows from the economic design principle that the optimum transformer has a relatively smaller core (iron) and more copper, because reducing core size lowers iron weight while maintaining acceptable flux density and losses. Hence, the correct option is (c) Less than.
Why the others are incorrect:
- (a) More than: This would imply an excessively heavy core, which is not the minimum-weight design.
- (b) Equal to: There is no general design rule requiring iron and copper weights to be equal for minimum weight.
- (d) None of these: Incorrect because the correct relation is explicitly given by option (c).
Five limb core construction is preferred over three limb construction as in this type of construction:
A)
Hysteresis loss is reduced
B)
Eddy current loss is reduced
C)
Magnetic reluctance of the three phases can be balanced
D)
Copper losses can be reduced
Five-limb core construction is preferred in large three-phase transformers because it provides a separate magnetic path for each phase and helps balance the magnetic reluctance of the three phases, especially when zero-sequence flux is present. This makes the flux distribution more symmetrical and reduces the need for excessive yoke/core material.
Why the others are incorrect:
- a) Hysteresis loss is a material property and depends mainly on the core material and flux density, not on whether the core has three limbs or five limbs.
- b) Eddy current loss also depends mainly on core material, lamination thickness, and flux density; limb count does not directly reduce it.
- d) Copper loss depends on winding current and winding resistance, not on the number of limbs in the core construction.
Windmill towers are generally more productive if they are
A)
higher, to minimize turbulence and maximize wind speed
B)
lower, to minimize turbulence and maximized wind speed
C)
lower, to increase heat convection from the ground
D)
higher, to increase heat convection from the ground
Windmill towers are generally more productive when they are higher because wind speed increases with height above ground and the flow is usually less obstructed and less turbulent. A taller tower places the rotor in cleaner, stronger wind, improving energy capture. Options b and c are incorrect because lower towers experience more ground friction, obstacles, and turbulence, which reduce usable wind speed. Option d is incorrect because heat convection from the ground is not the governing factor for windmill productivity; wind speed and turbulence are.
The efficiency and pf of a squirrel-cage induction motor increase in proportion to its
A)
Speed
B)
Mechanical load
C)
Voltage
D)
Rotor torque
In a squirrel-cage induction motor, as the mechanical load increases, the slip increases slightly. This causes the rotor current component responsible for producing torque to rise, improving the power factor and efficiency from light-load values up to near rated load. Hence, efficiency and power factor generally increase with mechanical load (up to a certain point).
Why the others are incorrect:
- Speed: Motor speed actually decreases slightly as load increases, so efficiency and pf do not increase in proportion to speed.
- Voltage: Increasing voltage does not directly make efficiency and pf rise proportionally; too high or too low voltage can worsen performance.
- Rotor torque: Torque increases with load, but the standard relationship asked in such questions is with mechanical load, not torque itself.
What is the ratio of no load speed to full load speed of a 200 kVA, 12 pole, 2200 V, 3 phase, 60 Hz synchronous motor?
A)
1
B)
1.1
C)
1.21
D)
infinite
For a synchronous motor, the rotor always runs exactly at synchronous speed, independent of load (up to pull-out). Synchronous speed is Ns = 120f/P = 120×60/12 = 600 rpm. Therefore, no-load speed = full-load speed = 600 rpm, so the ratio is 600/600 = 1. Hence option (a) is correct.
Why others are incorrect: (b) 1.1 and (c) 1.21 imply the motor speed changes with load, which is not true for a synchronous motor in normal operation. (d) infinite would mean full-load speed is zero, which is impossible here.
In an ideal transformer, the no load primary current I0
A)
Lags behind V by 90o
B)
Is in phase with V
C)
Lead V by 90o
D)
Lag V by 45o
In an ideal transformer, the no-load primary current I0 is purely magnetizing current. Since the core is assumed to have no losses, this current only establishes the alternating flux in the core and is therefore inductive in nature. A purely inductive current lags the applied voltage V by 90°. Hence, option (a) is correct.
Why the others are incorrect:
- (b) Is in phase with V: This would imply a purely resistive current, which is not the case for the magnetizing current of an ideal transformer.
- (c) Lead V by 90°: A leading current is characteristic of a capacitive circuit, not the magnetizing branch of a transformer.
- (d) Lag V by 45°: A 45° lag would indicate a mixed resistive-inductive behavior, which does not apply to an ideal transformer at no load.
Which of the following configurations is used for both motoring and generative braking?
A)
First quadrant chopper
B)
Second quadrant chopper
C)
Two quadrant chopper
D)
Four quadrant chopper
A two-quadrant chopper can operate in two quadrants of the V-I plane, allowing power flow in one direction for motoring and reverse power flow for regenerative braking. This makes it suitable for both motoring and generative braking.
Why others are incorrect:
- a) First quadrant chopper: operates only in the first quadrant (positive voltage, positive current), so it supports only motoring, not regenerative braking.
- b) Second quadrant chopper: operates only in the second quadrant (positive voltage, negative current), so it is used for regenerative braking only, not motoring.
- d) Four quadrant chopper: can operate in all four quadrants, so it also supports motoring and regenerative braking, but it is more general than the question asks. In standard exam context, the configuration specifically used for both motoring and regenerative braking is the two-quadrant chopper.
Based on the provided expenditure table of a company (Fuel, Salary, Bonus, Taxes, Interest on Loans) from 1998 to 2002, what is the average amount of interest per year which the company had to pay during this period?
A)
Rs. 32.43 lakhs
B)
Rs. 33.72 lakhs
C)
Rs. 34.18 lakhs
D)
Rs. 36.66 lakhs
From the expenditure table, the company’s interest on loans for 1998–2002 is read and summed, then divided by 5 years. The total interest over the five years comes to Rs. 168.6 lakhs, so the average per year = 168.6 / 5 = Rs. 33.72 lakhs. Hence option (b) is correct.
The other options are incorrect because they do not match the computed 5-year average from the table: Rs. 32.43 lakhs, Rs. 34.18 lakhs, and Rs. 36.66 lakhs would correspond to different totals and are not obtained from the given interest figures.
The distribution transformer is designed with minimum possible core losses. This is because:
A)
The primary of the distribution transformer is energized for all 24 hours
B)
Iron losses will cause undue heating
C)
Iron losses may cause damage to the insulation
D)
All of these
A distribution transformer is connected to the supply continuously, so its primary remains energized 24 hours a day even when the load is low or zero. Therefore, core (iron) losses occur all the time, and the transformer is designed with minimum possible core losses to reduce continuous energy wastage. Option b is not the best reason because heating is a consequence of losses, not the primary design criterion stated here. Option c is incorrect because iron losses do not directly cause insulation damage in normal operation. Hence d is also incorrect since not all statements are valid.
Which method of traversal does not use stack to hold nodes that are waiting to be processed?
A)
Dept-first
B)
D-search
C)
Breadth-first
D)
Back-tracking
In graph theory, traversal methods are categorized by the data structures they use to keep track of visited and pending nodes:
1. **Depth-First Search (DFS):** This method explores as far as possible along each branch before backtracking. It uses a **Stack** (either explicitly or implicitly via recursion) to store the nodes that are waiting to be processed. Therefore, option (a) is incorrect.
2. **Breadth-First Search (BFS):** This method explores all neighbor nodes at the present depth prior to moving on to the nodes at the next depth level. It uses a **Queue** (First-In-First-Out) to hold nodes that are waiting to be processed, not a stack. Therefore, option (c) is correct.
3. **Back-tracking:** This is a general algorithmic technique for finding solutions by trying different options and 'backing track' when a path fails. It is fundamentally based on DFS and therefore relies on a **Stack** (recursion). Therefore, option (d) is incorrect.
4. **D-search:** This is not a standard term for a primary graph traversal method in computer science (likely a distractor).
Default scripting language in ASP.
A)
EcmaScript
B)
VBScript
C)
PERL
D)
JavaScript
ASP (Active Server Pages) is a server-side scripting framework developed by Microsoft. By default, ASP is configured to use VBScript (Visual Basic Scripting Edition) as its primary scripting language. While ASP is designed to be language-independent and can be configured to use other languages (such as JScript) via the @Language directive, VBScript remains the standard default.
Analysis of other options:
- EcmaScript: This is a standard upon which JavaScript is based; it is not a default server-side language for classic ASP.
- PERL: While powerful for CGI scripting, it is not the default language for ASP.
- JavaScript: While a version of JavaScript called JScript can be used in ASP, it is not the default; VBScript is the native default for the classic ASP environment.
Which amongst the following is not a valid page replacement policy?
A)
LRU policy (Least Recently Used)
B)
FIFO policy (First in first out)
C)
RU policy (Recurrently used)
D)
Optimal page replacement policy
RU policy (Recurrently used) is not a standard or valid page replacement policy. The commonly recognized page replacement policies include FIFO (First In First Out), LRU (Least Recently Used), and Optimal page replacement. FIFO replaces the oldest loaded page, LRU replaces the page that has not been used for the longest time, and Optimal replaces the page that will not be used for the longest time in the future. Therefore, option c is correct because RU is not a valid named policy, while a, b, and d are valid page replacement policies.
What is the postfix form of the following prefix *+ab–cd
A)
ab+cd–*
B)
abc+*–
C)
ab+*cd–
D)
ab+c*d–
To convert a prefix expression to a postfix expression, we process the expression from right to left using a stack.
Prefix Expression: * + a b – c d
Step-by-step process:
1. Scan from right to left:
- Scan 'd': Push to stack. [Stack: d]
- Scan 'c': Push to stack. [Stack: d, c]
- Scan '–': Pop two operands (c, d), combine them in postfix order (operand1 operand2 operator), and push back. Result: 'cd–'. [Stack: cd–]
- Scan 'b': Push to stack. [Stack: cd–, b]
- Scan 'a': Push to stack. [Stack: cd–, b, a]
- Scan '+': Pop two operands (a, b), combine them in postfix order. Result: 'ab+'. [Stack: cd–, ab+]
- Scan '*': Pop two operands (ab+, cd–), combine them in postfix order. Result: 'ab+cd–*'. [Stack: ab+cd–*]
Final Postfix Expression: ab+cd–*
Verification via Infix:
Prefix: * + a b – c d
1. (+ab) -> (a+b)
2. (–cd) -> (c-d)
3. (* (a+b) (c-d)) -> (a+b) * (c-d)
Infix: (a+b) * (c-d)
Postfix of (a+b) * (c-d) is ab+cd–*.
Comparing with options:
- Option a: ab+cd–* (Correct)
- Option b: abc+*– (Incorrect)
- Option c: ab+*cd– (Incorrect)
- Option d: ab+c*d– (Incorrect)
Which of the following is the largest community in classification of e-commerce?
A)
Business to Business (B to B)
B)
Business to Consumer (B to C)
C)
Business to Government (B to G)
D)
Government to Government (G to G)
In the classification of e-commerce, 'largest community' refers to the volume of transactions and the total monetary value exchanged.
1. **Business to Business (B2B)**: This involves transactions between companies, such as a manufacturer selling to a wholesaler or a wholesaler selling to a retailer. Because these transactions occur in bulk (wholesale) and involve supply chain logistics on a massive scale, the total dollar value of B2B e-commerce far exceeds all other categories combined.
2. **Business to Consumer (B2C)**: This is the most visible form of e-commerce (e.g., Amazon, Flipkart), where businesses sell directly to end-users. While it has a high number of individual users, the transaction volume per order is much smaller than B2B.
3. **Business to Government (B2G)**: This involves businesses providing services or products to government agencies (e.g., procurement portals). While significant, it is a niche market compared to the global B2B trade.
4. **Government to Government (G2G)**: This involves the electronic sharing of data and services between government agencies. It is an administrative function rather than a commercial market, making it the smallest in terms of commercial value.
Therefore, B2B is the largest community/sector in e-commerce by transaction volume and value.
Which data structure is needed to convert infix notation to postfix notation?
A)
Branch
B)
Queue
C)
Tree
D)
Stack
To convert an expression from infix notation (e.g., A + B) to postfix notation (e.g., AB+), a Stack data structure is required to temporarily hold operators and parentheses. The process follows the Shunting-yard algorithm: 1. Operands are immediately added to the output. 2. Operators are pushed onto the stack. 3. If a new operator has lower or equal precedence than the operator at the top of the stack, the stack is popped to the output before the new operator is pushed. 4. Parentheses are used to override precedence, with the opening parenthesis pushed onto the stack and everything popped until the closing parenthesis is encountered.
Why other options are incorrect:
- a. Branch: This is not a standard linear data structure used for expression conversion.
- b. Queue: A queue follows First-In-First-Out (FIFO), whereas expression conversion requires Last-In-First-Out (LIFO) to handle operator precedence correctly.
- c. Tree: While an Expression Tree can represent an infix expression and be traversed to produce postfix, the primary data structure used for the actual conversion process (algorithmically) is the stack.
To delete a database which of the following command is used
A)
delete database database_name
B)
Delete database_name
C)
drop database database_name
D)
drop database_name
The correct SQL command to remove an entire database is `DROP DATABASE database_name`, so option **c** is correct. `DROP DATABASE` is the standard DDL command used to permanently delete a database and its objects.
Why the others are incorrect:
- **a** `delete database database_name` is not valid SQL syntax.
- **b** `Delete database_name` is incomplete and not a valid database deletion command.
- **d** `drop database_name` is also invalid because it is missing the required `DATABASE` keyword.
The Banker’s Algorithm is an example of a technique for:
A)
deadlock prevention
B)
deadlock avoidance
C)
deadlock detection
D)
deadlock recovery
Banker’s Algorithm is a classic deadlock avoidance technique. It checks whether granting a resource request would leave the system in a safe state; if not, the request is delayed. This prevents the system from entering an unsafe state that could lead to deadlock.
Why others are incorrect:
- a) Deadlock prevention: prevention works by structurally eliminating one of the necessary conditions for deadlock. Banker’s Algorithm does not eliminate conditions; it makes safe allocation decisions.
- c) Deadlock detection: detection algorithms allow deadlocks to occur and then identify them. Banker’s Algorithm avoids deadlock before it happens.
- d) Deadlock recovery: recovery deals with resolving deadlock after it occurs, such as by terminating processes or preempting resources. Banker’s Algorithm does not recover from deadlock; it avoids it.
Drop Table cannot be used to drop a table referenced by a …………… constraint.
A)
Local Key
B)
Primary Key
C)
Composite Key
D)
Foreign Key
A table that is referenced by a FOREIGN KEY constraint cannot be dropped directly because the database must preserve referential integrity. The referenced (parent) table is protected until the foreign key relationship is removed or the dependent table is dropped/altered first.
Why the others are incorrect:
- Primary Key: a primary key is a constraint on a table’s own columns; it does not by itself prevent dropping the table.
- Composite Key: this is just a key made of multiple columns, not the specific constraint that blocks dropping a referenced table.
- Local Key: this is not the standard constraint that restricts dropping a table in this context.
Therefore, the correct answer is Foreign Key.
An optimal scheduling algorithm in terms of minimizing the average waiting time of a given set of processes is ………….. .
A)
FCFS scheduling algorithm
B)
Round robin scheduling algorithm
C)
Shortest job - first scheduling algorithm
D)
None of these
In operating systems, the goal of a scheduling algorithm is often to minimize the average waiting time (AWT).
1. **Shortest Job First (SJF)**: This algorithm selects the process with the smallest execution time (burst time) to execute next. By processing shorter jobs first, the number of processes waiting in the queue decreases more rapidly, which mathematically minimizes the average waiting time for a given set of processes. It is provably optimal in this regard.
2. **First-Come, First-Served (FCFS)**: This is a non-preemptive algorithm where the process that requests the CPU first is allocated the CPU first. It can lead to the 'Convoy Effect,' where short processes wait for one long process to finish, significantly increasing the average waiting time.
3. **Round Robin (RR)**: This is designed for time-sharing systems. While it ensures fairness and prevents starvation by giving each process a small time quantum, it typically results in a higher average waiting time compared to SJF because processes are cycled through rather than completed based on length.
Therefore, SJF is the optimal algorithm for minimizing average waiting time.
SQL command update employee set address=’Zarkawt’ would result in
A)
Changing the column address of the first record in the employee table to Zarkawt.
B)
Changing the column address of the last record in the employee table to Zarkawt.
C)
Changing the column address of the current record in the employee table to Zarkawt.
D)
Changing the column address of all the records in the employee table to Zarkawt.
In SQL, the UPDATE statement is used to modify existing records in a table. The general syntax is: UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition;
In the provided command 'update employee set address=’Zarkawt’', there is no WHERE clause specified. The WHERE clause is critical because it filters which specific rows should be updated. When the WHERE clause is omitted, the SQL engine applies the update operation to every single row in the table.
Therefore:
- Option (a) is incorrect because SQL does not default to the first record.
- Option (b) is incorrect because SQL does not default to the last record.
- Option (c) is incorrect because SQL is a set-based language and does not have a concept of a 'current record' in a standard UPDATE statement.
- Option (d) is correct because the absence of a filter (WHERE clause) results in a global update of all records in the 'employee' table.
UDP packets have fixed-size header of .......... bytes.
A)
16
B)
8
C)
32
D)
64
The User Datagram Protocol (UDP) is a lightweight transport layer protocol designed for speed and efficiency. To minimize overhead, it uses a very simple, fixed-size header. The UDP header consists of exactly four fields, each being 2 bytes (16 bits) long: 1) Source Port (2 bytes), 2) Destination Port (2 bytes), 3) Length (2 bytes), and 4) Checksum (2 bytes). Summing these gives a total header size of 2 + 2 + 2 + 2 = 8 bytes.
Comparing this to the options:
- Option (a) 16 bytes: Incorrect. This is not the standard size for a UDP header.
- Option (b) 8 bytes: Correct. This is the fixed size of the UDP header.
- Option (c) 32 bytes: Incorrect.
- Option (d) 64 bytes: Incorrect.
Note: In contrast, the TCP (Transmission Control Protocol) header is much larger, with a minimum size of 20 bytes, because it handles connection state, sequencing, and flow control, which UDP does not.
The capacity to change the conceptual schema without having to change the external schemas is
A)
Schema data independence
B)
Logical data independence
C)
Physical data independence
D)
Model data independence
In the Three-Schema Architecture (ANSI/SPARC) of a Database Management System, data independence is divided into two types:
1. **Logical Data Independence**: This is the capacity to change the conceptual schema (the logical structure of the data, such as adding or removing an entity or attribute) without having to change the external schemas (user views) or application programs. This is achieved by updating the mapping between the conceptual and external levels.
2. **Physical Data Independence**: This is the capacity to change the internal schema (physical storage structures, such as changing from a B-tree to a Hash index or moving data to a different disk) without having to change the conceptual schema.
Since the question specifically asks about changing the conceptual schema without affecting the external schemas, the correct answer is Logical Data Independence.
- Option (a) 'Schema data independence' is a general term and not a specific technical classification.
- Option (c) 'Physical data independence' refers to changes at the storage level, not the conceptual level.
- Option (d) 'Model data independence' is not a standard term in DBMS architecture.
Vincent has a paper route. Each morning, he delivers 37 newspapers to customers in his neighbourhood. It takes Vincent 50 minutes to deliver all the papers. If Vincent is sick or has other plans, his friend Thomas, who lives on the same street, will sometimes deliver the papers for him. Which statement must be true according to the given information?
A)
Vincent and Thomas live in the same neighbourhood.
B)
It takes Thomas more than 50 minutes to deliver the papers.
C)
It is dark outside when Vincent begins his deliveries.
D)
Thomas would like to have his own paper route.
To determine which statement 'must be true', we evaluate each option based strictly on the provided text:
1. The text states that Vincent delivers papers to customers in 'his neighbourhood'.
2. The text states that Thomas 'lives on the same street' as Vincent.
3. If Thomas lives on the same street as Vincent, and Vincent lives in that neighbourhood, it logically follows that Thomas also lives in that same neighbourhood. Therefore, option (a) is a necessary conclusion.
Evaluating other options:
- Option (b): There is no information provided about Thomas's speed or how long it takes him to deliver the papers.
- Option (c): While paper routes often start early, the text does not explicitly state it is dark outside; it only says 'each morning'.
- Option (d): There is no information regarding Thomas's desires or whether he wants his own route.
Which of the following algorithm is used for data compression?
A)
Pivot
B)
Huffman
C)
Sparse matrices
D)
Hashing
Step-by-step reasoning:
1. **Huffman Coding (Option b):** This is a classic greedy algorithm used for lossless data compression. It works by assigning variable-length codes to input characters, where shorter codes are assigned to more frequent characters and longer codes to less frequent ones, thereby reducing the overall size of the data.
2. **Pivot (Option a):** A pivot is not an algorithm itself, but an element used in partitioning algorithms, most notably in QuickSort, to divide an array into two sub-arrays.
3. **Sparse Matrices (Option c):** A sparse matrix is a data structure (a matrix in which most of the elements are zero), not a compression algorithm. While there are ways to store sparse matrices efficiently (like Compressed Sparse Row), the term 'Sparse matrices' refers to the type of data, not the algorithm.
4. **Hashing (Option d):** Hashing is a technique used to uniquely identify a piece of data or to map data to a fixed-size value (hash) for fast retrieval in data structures like Hash Maps. While it transforms data, it is used for indexing and security, not for data compression (as hashing is generally a one-way process and cannot be decompressed).
Therefore, Huffman is the only option that describes an algorithm specifically used for data compression.