To determine the work done in a free expansion process, we need to understand the definition of free expansion and the formula for work done in thermodynamics. Free expansion is an irreversible process where a gas expands into a vacuum without any external resistance. The work done by a system is generally defined by the integral of pressure with respect to volume change.
Correct Option: A) Zero. In a free expansion process, a gas expands into a vacuum, meaning there is no external pressure against which the gas has to do work. Consequently, the work done by the system is zero.
The internal energy of an ideal gas is a fundamental concept in thermodynamics. To determine what it depends on, we need to recall the kinetic theory of gases and the definition of internal energy for an ideal gas.
A) A function of temperature only
As explained above, for an ideal gas, internal energy is entirely due to the kinetic energy of its molecules, which in turn depends only on the absolute temperature. Pressure and volume changes at constant temperature do not affect the internal energy of an ideal gas.
The question asks to identify the thermodynamic process where no heat enters or leaves the system. This directly refers to the definition of a specific type of thermodynamic process. We need to recall the definitions of the processes listed in the options.
C) Isentropic — An isentropic process is defined as a thermodynamic process in which the entropy of the fluid or gas remains constant. For a reversible process, this condition (\(\Delta S = 0\)) implies that there is no heat transfer (\(Q = 0\)) into or out of the system. Therefore, a reversible adiabatic process is an isentropic process. In the absence of "adiabatic" as an option, "isentropic" is the correct answer.
The question asks about the indicator for the ignition quality of diesel fuel. This is a direct knowledge-based question related to internal combustion engines and fuel properties. We need to identify the specific number used to quantify diesel's ignition characteristics.
B) Cetane number is the standard measure for the ignition quality of diesel fuel. It indicates the readiness of the fuel to ignite under compression. A higher cetane number means the fuel ignites more quickly and smoothly in a diesel engine.
The question asks about the type of fuel used in a Spark Ignition (SI) engine. Understanding the fundamental working principle of an SI engine and its fuel requirements is key to answering this question.
Correct Option: B) Petrol is the fuel primarily used in Spark Ignition (SI) engines. These engines rely on a spark plug to ignite a pre-mixed charge of fuel and air, a process for which petrol's volatility is well-suited.
The question asks about the primary mode of heat transfer in solids. We need to recall the definitions of the three main modes of heat transfer: conduction, convection, and radiation, and identify which one is characteristic of solids.
A) Conduction is the process of heat transfer through direct contact between particles, without any bulk movement of the material. This is the primary and most significant way heat moves through solids, as their particles are fixed in position and transfer energy through vibrations and collisions.
The question asks for the definition of a perfect black body. We need to understand the fundamental properties of an ideal black body in physics and thermodynamics.
D) One which absorbs all radiant energy at all wavelengths
This option accurately defines a perfect black body. It emphasizes that the absorption is complete (all radiant energy) and universal across the electromagnetic spectrum (at all wavelengths). This is the most precise and comprehensive definition.
The question asks about the cause of weld spatter, a common welding defect. We need to identify which of the given options directly leads to the formation of spatter.
B) High welding current is a primary cause of weld spatter. Excessive current leads to an unstable arc, overheating of the weld pool, and violent expulsion of molten metal droplets, which solidify as spatter.
Arc welding produces an extremely bright and hot electric arc. This arc emits various forms of electromagnetic radiation, some of which are highly damaging to human eyes. The question asks what specific types of radiation eyes need protection against during this process.
Correct Option: D) Ultraviolet and infrared radiation. Arc welding arcs produce significant amounts of both ultraviolet and infrared radiation, which can cause severe and permanent eye damage if not properly protected against. Welding helmets with specialized filters are designed to block these harmful radiations.
The question asks about the material typically used for a lathe bed. The choice of material for a machine tool component like a lathe bed is crucial as it directly impacts the machine's stability, vibration damping, wear resistance, and manufacturing cost. We need to evaluate the properties of the given options against these requirements.
B) Cast iron is the most suitable material for a lathe bed due to its high compressive strength, excellent vibration damping properties, good wear resistance for guideways, and cost-effectiveness in casting large, complex shapes. These properties are essential for maintaining the accuracy and stability of the lathe during operation.