Defence Research & Development Organisation Apprenticeship Trainee Interview Questions and Answers for Experienced

Q1. Explain your B Tech project in detail
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Q2. Why HAL u want to join
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Q1. Related to aeronautics
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Q1. Salary discussion,documentation and bond details
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Q1. Why the brittle material fail as spiral fracture surface under torsion
Ans. 
Brittle materials fail as spiral fracture surface under torsion due to their inability to deform plastically.
• Brittle materials lack ductility and are unable to deform plastically under stress

• Under torsion, the material experiences shear stress which leads to the formation of spiral fracture surfaces

• The lack of plastic deformation causes the material to fail catastrophically along these spiral paths

• Examples of brittle m...read more
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Q2. What is entropy
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Entropy is a measure of disorder or randomness in a system.
• Entropy is a thermodynamic property that quantifies the amount of energy in a physical system that is not available to do work.

• It is a measure of the number of possible arrangements of particles in a system.

• Entropy tends to increase in isolated systems over time, leading to a state of maximum disorder or equilibrium.

• An example of entropy is the melting of ice -...read more
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Q3. How to find natural frequency practically
Ans. 
Natural frequency can be found practically by conducting modal analysis or using specialized equipment like accelerometers.
• Conduct modal analysis by applying a force or impulse to the structure and measuring the resulting vibrations.

• Use specialized equipment like accelerometers to measure the vibrations of the structure.

• Calculate the natural frequency using the formula: f = 1 / (2π√(k/m)), where f is the natural freque...read more
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Q4. What is Fast Fourier transform
Ans. 
Fast Fourier Transform (FFT) is an algorithm used to compute the Discrete Fourier Transform (DFT) of a sequence or signal.
• FFT is used to analyze the frequency content of a signal by decomposing it into its constituent frequencies.

• It is commonly used in signal processing, image processing, audio analysis, and many other fields.

• FFT algorithms are much faster than the naive DFT computation, making it practical for real-ti...read more
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Q5. How FFT is different from DFT
Ans. 
FFT is a faster algorithm for calculating DFT
• FFT is faster than DFT in terms of computation time

• FFT uses a divide-and-conquer approach to reduce the number of operations

• DFT computes all frequencies while FFT only computes the frequencies of interest

• FFT is commonly used in signal processing applications
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Q1. Distillation ,heat exchanger
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Q2. Tpye of distillation
Ans. 
Distillation is a process used to separate mixtures based on differences in boiling points.
• Distillation involves heating a mixture to vaporize the more volatile component.

• The vapor is then cooled and condensed back into a liquid, resulting in the separation of the components.

• Types of distillation include simple distillation, fractional distillation, and steam distillation.

• Simple distillation is used to separate liquids...read more
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Q1. What is refrigeration cycle
Ans. 
The refrigeration cycle is a process that removes heat from a space or substance to lower its temperature.
• The cycle consists of four main components: compressor, condenser, expansion valve, and evaporator.

• The compressor increases the pressure and temperature of the refrigerant gas.

• The high-pressure gas then flows into the condenser where it releases heat and becomes a high-pressure liquid.

• The liquid refrigerant passes ...read more
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Q2. What is air conditioner
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An air conditioner is a device that cools and dehumidifies the air in a room or building.
• Air conditioners use refrigeration cycles to remove heat and moisture from the air.

• They consist of components such as compressors, condensers, evaporators, and fans.

• Air conditioners can be used for both cooling and heating purposes.

• Examples of air conditioners include window units, split systems, and central air conditioning system
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Q3. How many types of condenser are tere
Ans. 
There are several types of condensers used in various industries and applications.
• Air-cooled condenser

• Water-cooled condenser

• Shell and tube condenser

• Plate condenser

• Evaporative condenser

• Surface condenser

• Finned tube condenser
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Q4. Primary secondary and condenser and ahu how to work explain
Ans. 
Primary, secondary, condenser, and AHU are components of a HVAC system.
• Primary and secondary refer to the two sides of a heat exchanger in the HVAC system.

• The primary side carries the hot fluid or refrigerant, while the secondary side carries the cool fluid or air.

• The condenser is a heat exchanger that removes heat from the refrigerant and converts it from a gas to a liquid.

• The AHU (Air Handling Unit) is responsible fo...read more
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Q5. How many types of chiller safety are there
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There are several types of chiller safety measures that are implemented to ensure safe operation and prevent accidents.
• Safety measures include pressure relief valves to prevent overpressure

• Temperature sensors to monitor and control the chiller's operating temperature

• Flow switches to detect and prevent low or no flow conditions

• High-pressure switches to protect against excessive pressure

• Low-pressure switches to prevent d...read more
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Q6. How much in resistance ohms
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The resistance is measured in ohms.
• Resistance is a measure of how much a material opposes the flow of electric current.

• The unit of resistance is ohms (Ω).

• Resistance can be calculated using Ohm's Law: R = V/I, where R is resistance, V is voltage, and I is current.

• Resistance can vary depending on the material, length, and cross-sectional area of a conductor.

• For example, a copper wire with a length of 1 meter and a cross-...read more
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Q7. How much sensor voltage
Ans. 
The sensor voltage varies depending on the specific sensor and its application.
• Sensor voltage is typically measured in volts (V).

• Different sensors may have different voltage ranges and requirements.

• For example, a temperature sensor may operate within a voltage range of 0-5V.

• Some sensors may require a specific voltage supply, while others may be designed to work with a wide range of voltages.

• It is important to consult t...read more
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Q8. Thermoelectric refrigeration system operate on the principle of peltier effect
Ans. Why is ammonia the only common refrigerant used in the absorption system
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Q9. Because ammonia is cheap readily available and has the highest efficiency
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Q1. How to major resistance by old method
Ans. 
Major resistance by old method involves using traditional techniques to determine the level of resistance in a material.
• Use manual testing methods such as scratch testing or hardness testing to assess resistance

• Refer to historical data or records of similar materials for comparison

• Consult with experienced professionals who have knowledge of traditional resistance testing methods
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