Online Preliminary Examination 2020 For B.Sc.-II Semester,Organized By Department Of Physics,Sgmm Hingna,Dist-naGPur

The total amount of energy in the universe is constant because of the law of conservation of energy. According to this law, energy cannot be created or destroyed, only transformed from one form to another. Therefore, the total amount of energy in the universe remains the same over time. This concept is supported by scientific evidence and is a fundamental principle in physics.

A reversible cycle consists of processes that can be reversed without any loss of energy. In this case, the answer states that there are 2 isothermal and 2 adiabatic processes. An isothermal process is one in which the temperature remains constant, while an adiabatic process is one in which there is no heat exchange between the system and its surroundings. Therefore, having 2 isothermal and 2 adiabatic processes in a reversible cycle ensures that the temperature remains constant at certain points and there is no heat exchange, making it a valid explanation for the correct answer.

Enthalpy is a measure of the total energy of a system, including both its internal energy and the energy required to do work on its surroundings. An increase in enthalpy indicates an increase in the total energy of the system, which means there must be an increase in the internal energy as well. Therefore, the correct answer is internal energy.

The statement "If two systems are both in equilibrium with a third system, they are in thermal equilibrium with each other" is the statement of the Zeroth law of thermodynamics. The Zeroth law states that if two systems are separately in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This law establishes the concept of temperature and allows for the measurement and comparison of temperatures between different systems. It forms the foundation for the development of the other laws of thermodynamics.

The average kinetic energy is given by 1.5 KT. This is because the average kinetic energy of a system is directly proportional to the temperature of the system. The constant of proportionality, denoted as K, represents the Boltzmann constant. Therefore, multiplying the temperature by 1.5 times the Boltzmann constant gives the average kinetic energy.

Driven harmonic vibration refers to a type of forced vibration in which an external force or driving force is applied to a system. This external force causes the system to vibrate at a frequency that is different from its natural frequency. The term "harmonic" indicates that the vibration follows a sinusoidal pattern, while "driven" implies that the vibration is caused by an external force rather than occurring naturally. Therefore, "Driven harmonic vibration" is an appropriate term to describe forced vibration.

A heat pump and a refrigerator can both be considered examples of a reversed heat engine. In a heat pump, heat is transferred from a colder area to a warmer area using mechanical work. This is the opposite of a traditional heat engine where heat is transferred from a hotter area to a colder area to produce work. Similarly, a refrigerator also transfers heat from a colder area (inside the refrigerator) to a warmer area (outside the refrigerator) using mechanical work. Therefore, both a heat pump and a refrigerator can be considered examples of reversed heat engines.

At low pressure, the gas molecules are far apart and experience weak intermolecular forces. This allows the gas to behave more like an ideal gas, where the volume of individual gas molecules is negligible compared to the total volume. At high temperatures, the kinetic energy of the gas molecules increases, causing them to move faster and collide more frequently. This also leads to a more ideal gas behavior, as the collisions become more elastic and the gas molecules occupy a larger space. Therefore, under conditions of low pressure and high temperature, a real gas most closely approaches the behavior of an ideal gas.

A compound pendulum refers to a rigid body that is suspended vertically and oscillates with a small amplitude under the force of gravity. Unlike a simple pendulum, which consists of a mass attached to a string or rod, a compound pendulum has a more complex structure, such as a bar or a physical object. The oscillation of a compound pendulum is influenced by both its mass and its distribution of mass, making it different from other types of pendulums mentioned in the options. Therefore, the correct answer is compound pendulum.

In a gas, the transport of momentum gives rise to the phenomenon of viscosity. Viscosity is a measure of a fluid's resistance to flow, and it is caused by the internal friction between different layers of the fluid as they move past each other. When momentum is transferred between gas molecules, it creates a shearing effect, causing the gas to exhibit viscosity. This property is important in understanding how gases flow and interact with each other and with solid surfaces. Conduction refers to the transfer of heat or electricity through a substance, diffusion refers to the movement of particles from an area of high concentration to an area of low concentration, and volume refers to the amount of space occupied by a gas.

The temperature of a gas molecule in a container is directly proportional to the mean free path of a gas molecule. This means that as the temperature increases, the mean free path also increases, and vice versa. The mean free path is the average distance a gas molecule travels between collisions with other molecules. When the temperature increases, the gas molecules gain more kinetic energy and move faster, leading to longer mean free paths.

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The equation DQ = dU + pdV represents the closed system. In this equation, DQ represents the heat added to the system, dU represents the change in internal energy of the system, and pdV represents the work done on the system. The equation shows that the heat added to the system is equal to the change in internal energy plus the work done on the system. This equation follows the first law of thermodynamics, which states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system.

Helium is the correct answer because it is an ideal gas that behaves closely to Boyle's law over a wider range of temperatures and pressures. Boyle's law states that at a constant temperature, the pressure and volume of a gas are inversely proportional. Helium, being a noble gas, has low intermolecular forces and is highly compressible, allowing it to exhibit a wide range of pressure and volume changes while still obeying Boyle's law.

When helium expands at room temperature, heating is produced. This is because helium gas molecules gain kinetic energy and move faster when they expand. As a result, the average temperature of the gas increases, leading to the production of heat.

A diatomic gas molecule consists of two atoms connected by a bond. Each atom has three degrees of freedom: translational motion in three dimensions. In addition to these six degrees of freedom, the diatomic molecule also has rotational motion around its center of mass. However, since it is a linear molecule, one of the three rotational degrees of freedom is restricted. Therefore, a diatomic gas molecule has a total of five degrees of freedom: three translational and two rotational.

The third law of thermodynamics states that it is impossible to reach absolute zero temperature in a finite number of operations. This means that no matter how many cooling or heat removal processes are applied, it is not possible to completely remove all heat from a system and reach absolute zero temperature. This law provides a fundamental limit to the cooling of objects and the behavior of systems at very low temperatures.

The term N.T.P. stands for Normal temperature and pressure. This term is commonly used in scientific and engineering contexts to specify standard conditions for measurements and calculations. Normal temperature is typically defined as 20 degrees Celsius or 293.15 Kelvin, while normal pressure is typically defined as 1 atmosphere or 101.325 kilopascals. These standard conditions allow for consistent and comparable results in experiments and calculations.

Boyle's law states that the pressure of a gas is inversely proportional to its volume, as long as the temperature and amount of gas remain constant. In order for Boyle's law to hold true, the gas must be "perfect" which means it follows the ideal gas law, where the gas particles have no volume and do not interact with each other. Additionally, the gas must have a constant mass and temperature, meaning that the number of gas particles and the temperature remain unchanged.

The constant used in pressure correction by Vander Waal is A. Unfortunately, without any further context or information provided in the question, it is difficult to provide a specific explanation for why A is the correct answer. Vander Waal's equation of state is commonly used to account for the non-ideal behavior of gases, and it involves the constants 'a' and 'b'. It is possible that A represents one of these constants in the equation. However, without additional information, it is not possible to provide a definitive explanation.

The correct answer is Q = 2π (energy stored in the system / energy lost per period). This formula is derived from the definition of the Quality Factor (Q) for a damped oscillator. The Q factor represents the ratio of energy stored in the system to the energy lost per period. Therefore, the correct formula is Q = 2π (energy stored in the system / energy lost per period).

The first law of thermodynamics states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system. This means that the internal energy of a system can be increased by adding heat to it or by doing work on it, and it can be decreased by removing heat from it or by the system doing work on its surroundings. The equation Internal Energy= (Heat added) - (work done) represents this relationship between heat, work, and internal energy.

The expansion device in a refrigeration system is responsible for reducing the pressure and temperature of the refrigerant before it enters the evaporator. The receiver is a component that stores excess liquid refrigerant and prevents it from entering the compressor. The evaporator is where the refrigerant absorbs heat from the surroundings and evaporates. Therefore, the expansion device is connected between the receiver and the evaporator to regulate the flow of refrigerant and ensure proper cooling efficiency.

The correct answer is ω2∙r. In simple harmonic motion (SHM), the maximum acceleration of a particle moving is directly proportional to the square of the angular frequency (ω) and the displacement (r) from the equilibrium position. Therefore, the product of ω2 and r gives the maximum acceleration of the particle.

Reynolds law holds good at constant volume. This means that the law applies when the volume of a system remains constant during a process. Reynolds law is a principle in fluid dynamics that relates the flow rate of a fluid to its viscosity and the pressure gradient across the system. It is commonly used to analyze fluid flow in pipes and channels.