Answer: a [Reason:] Nitriding is a diffusion process for surface hardening of steels. It involves the addition of nitrogen atoms to obtain the desired hardness of steel components.

Answer: b [Reason:] Nitriding differs from case-hardening as they contain nitrogen instead of carbon. Nitriding requires special steels called ‘Nitralloy’. This is because hardness depends on the formation of very hard compounds of nitrogen and metal such as aluminum, chromium, and vanadium present in the steel.

Answer: c [Reason:] Nitriding is generally not preferred for plain carbon steels. This is due to the formation of iron nitrides formed to a considerable depth below the surface of the steel. This causes embrittlement of the material.

Answer: a [Reason:] Before nitriding is carried out, it is required that the workpieces are heat treated. This is done in order to produce the required properties in the core. The parts are heat treated at just about 500^oC for several hours.

Answer: b [Reason:] Before nitriding is carried out, it is required that the workpieces are heat treated to produce the required properties in the core. The parts are heat treated at around 500^oC for a period of 40 to 100 hours. This process takes place in a gas-tight chamber through which ammonia gas is allowed to circulate.

Answer: c [Reason:] Ordinary atmospheric nitrogen exists in the form of molecules (N2). As a result, these molecules cannot be absorbed by the steel, which is necessary for the nitriding process. Therefore, atmospheric nitrogen is not suitable for nitriding process.

Answer: d [Reason:] Nitriding has an edge over case-hardening as the surface formed is extremely hard. The treatment is conducted at comparatively low temperatures due to which the cracking and distortion effects are minimized. Nitriding is generally an expensive process. However, it may be cheaper when a large number of components are to be treated.

Answer: a [Reason:] Cyaniding is a process of hardening the surface of steel components through the addition of nitrogen and carbon. It is done by immersing the workpiece is a cyanide bath. Usually, plain carbon steels and alloying steels containing 0.2% carbon are hardened using this process.

Answer: c [Reason:] Cyaniding is a process of hardening the surface of steel components through the addition of nitrogen and carbon. It is done by immersing the workpiece is a bath of molten sodium cyanide and sodium carbonate. This process is conducted at a temperature of 950^oC. This causes the formation of hard iron nitrides which leads to surface hardening of the material.

Answer: c [Reason:] Normalising is a process similar to annealing, which helps to refine grain structure, increase strength, and relieve stresses and other properties. Cooling for annealing is done in a furnace, whereas it is done in still air for normalising.

Answer: d [Reason:] Normalising is a process similar to annealing, where the material is subjected to temperature changes to alter their properties. This process is particularly employed for low and medium carbon steels, as well as alloy steels.

Answer: c [Reason:] For hypoeutectoid steels, normalising is done by heating the steel 50-60^oC C above its upper critical temperature (A3 line). For hypereutectoid steels, it is heated above the Acm line. The steel is held at that temperature for some time and then allowed to cool in still air.

Answer: b [Reason:] Normalising is carried out by heating of the steel at higher temperatures (compared to annealing) and then cooling it in still air. Since cooling is different at different locations, their properties will also vary. It also provides a fine grain structure and is less time-consuming.

Answer: c [Reason:] The type of structure obtained by normalising largely depends on the thickness of the cross-section of the material, as this also affects the rate of cooling. Thin sections tend to give a finer grain structure than thick sections.

Answer: b [Reason:] Normalising produces microstructure containing ferrite (white network) and pearlite (dark area) for hypoeutectoid steels. For eutectoid steels, the microstructure is only pearlite. Meanwhile, for hypereutectoid steels, it is a pearlite and cementite microstructure.

Answer: d [Reason:] The rate of cooling heavily depends on the quenching medium used. 5-10% caustic soda and 5-20% NaCl are the two most popular media in terms of severity, followed by cold and warm water. This is followed by mineral, animal, and vegetable oils. Finally, air has the lowest severity of the preferred media.

Answer: b [Reason:] Oils are generally more effective as quenching media as compared to air. In decreasing order, mineral oil, animal oil, and vegetable oil are widely used. The commonly used vegetable oils are linseed, cottonseed, and rapeseed.

Answer: c [Reason:] Mineral oils are obtained during the refining of crude petroleum. These are widely used as quenching media due to their severity of quench. Mineral oils are used in hardening alloy steels.

Answer: b [Reason:] Water produces the most severe quench followed by oils and air. For the quenching of carbon and low alloy steels, water or an aqueous solution of NaOH or NaCl is used.

Answer: c [Reason:] In general, both vapor-jacket and liquid-cooling are slow cooking stages. However, liquid-cooling is the slowest as all the heat transfer occurs through conduction across the solid-liquid interface.

Answer: b [Reason:] The vapor-jacket stage of quenching is a slow cooling stage since all the heat is transported through a gas by conduction and radiation. This stage occurs when the metal is above the boiling point of the quenchant.

Answer: c [Reason:] Nylon is a standard name for a group of polyamide polymers containing the amide group –CONH. It is primarily used as a fiber but also finds its applications as an engineering plastic. Nylon has good mechanical, chemical, and frictional properties.

Answer: b [Reason:] Nylon is a crystalline and thermoplastic polymer. It had a good tensile strength of 105 psi and a specific gravity of 1.14. The melting point of Nylon 6 is 223^oC, whereas that of Nylon 6,6 is 264^oC.

Answer: a [Reason:] Nylon is a material that possesses good abrasion and impact resistance. However, it absorbs a lot of moisture. This results in changes in dimensions by more than 2% in a 100% relative humidity surrounding.

Answer: b [Reason:] Nylon’s drastic drawback is regarded as its high moisture absorption. At 65% relative humidity, the moisture absorption is 4%, whereas, at 100% relative humidity, it is 2%.

Answer: b [Reason:] Nylon is regarded as a material having good load-bearing characteristics. It can be extruded over a wide range. Nylon 6 has an elongation of 30-220%, whereas that of Nylon 6,6 is 60%.

Answer: b [Reason:] Nylon is a self-extinguishing material that is difficult to ignite. It has the ability to melt and form beads. Its maximum service temperature range is 250-300 F.

Answer: d [Reason:] Nylon 610 is a material formed by the condensation of sebacic acid and hexamethylenediamine. It has been trademarked by the name of Tynex.

Answer: a [Reason:] Nylon 11 is a material made from castor bean oil that has a French origin. It is known by its trademark name of Rilsan. The other name of Nylon 12 is Rilsan 12.

Answer: c [Reason:] Nylon 9 is a material made from 9-aminononanoic acid present in soybean oil. It has higher electrical resistance than both Nylon 6 and Nylon 6,6. Therefore, it is mainly used in metal coatings and electrical parts.

Answer: c [Reason:] Nylon generally holds good electrical resistance, even though it may accumulate static charges. Nylon 6 and Nylon 6,6 have dielectric strengths of 385 V/mil. The dielectric strength of Nylon 610 is 470 V/mil.

Answer: a [Reason:] The optimum quality of rubber is achieved when 1 to 5 parts of sulfur are added to 100 parts of rubber. The material becomes hard and less extensible when this proportion is increased.

Answer: c [Reason:] Vulcanization of rubber drastically improves the strength of a rubber. Vulcanized rubber exhibits a tensile strength of about 700 kg/cm² and an elongation at break of 800%. Unvulcanized rubber has a low tensile strength of around 70 kg/cm².

Answer: c [Reason:] Calendering is a forming operation by which rubber compounds are spread like sheets over a fabric. The calendering unit involves three to five rolls in different combinations.

Answer: d [Reason:] Sheeting involves the production of long and continuous sheets of a rubber compound. These sheets are then mechanically pressed from a thin layer to a sheet of fabric. Skim coating is the application of a thin sheet of rubber to the sheet of fabric.

Answer: a [Reason:] Tubing is the most economical and widely used method of rubber preparation. Here, the compound is heated in a mill and then inserted directly into the extruder. The extruder is also known as a Tubing machine. This extrudes the rubber of the desired shape and size.

Answer: a [Reason:] This figure illustrates the arrangement of the rolls, fabric, and coating material for calendering. Here, the arrangement is a Z-type 4-roll calendar extending on both sides.

Answer: b [Reason:] A screw mechanism is used to force the rubber into a tightly closed mold. This force, under a high pressure, increases the temperature and reduces the time required.

Answer: a [Reason:] Epoxy adhesive is a copolymer made of a resin and a hardener. They have a faster curing rate and are used for quick fixes. These adhesives possess good resistance to heat, chemicals, and creep.

Answer: b [Reason:] Araldite glue is a common adhesive used to join small and lightweight metals. It is extensively used by automobile companies like Audi, Bentley, and even Lamborghini.

Answer: d [Reason:] Polyurethane glues when in contact with moisture result in speedy curing of materials. They are primarily used are woodworking adhesives. Gorilla Glass is a widely used Polyurethane adhesive.

Answer: a [Reason:] Dendrite acts as both an adhesive and a cement brand. Contact adhesives are used in applications involving strong bonds with great shear resistance. These are applied to two surfaces, left to dry for a while, and they are made to contact each other.

Answer: d [Reason:] Blu Tack is a common pressure sensitive type of adhesive used on surfaces to attach lightweight objects. Pressure sensitive adhesives, as the name suggests, form a bond on the application of pressure.

Answer: d [Reason:] Wood glue, as the name suggests, is an adhesive used to join wood pieces and materials together. Along with the above-mentioned types, wood glues include urea-formaldehyde, cyanoacrylate, and polyvinyl acetate among others.

Answer: c [Reason:] From the time that a product or service is opened for use till the time it retires is recorded as its shelf life. In common terms, shelf life is known as the expiration date.

Answer: c [Reason:] Cyanoacrylate is an adhesive belonging to the wood glue family. These are commonly used in household and medical applications. This adhesive has a short shelf life of one year if unopened and of one month once it has been opened.

Answer: a [Reason:] Electromagnetic induction is the production of a voltage in an electrical conductor having a varying magnetic field. It is defined as Weber per square meter or Tesla (T). Saturation induction Ba and residual induction BT are also given by the same unit.

Answer: c [Reason:] Permeability in electromagnetism is defined as its ability of formation of a magnetic field in itself. Magnetic permeability is given as Henry per meter (H m-1) and is denoted by the symbol .

Answer: c [Reason:] The strength of a magnetic field produced as a result of moving charges and dipoles is known as magnetic field strength (H). Mathematically, it is denoted by with its SI units given in ampere per meter (A m-1).

Answer: b [Reason:] Permeability is defined as the ability of a material to form a magnetic field within itself. The permeability of free space is denoted by and has a constant value of 4 * 10^-7 H m^-1.

Answer: b [Reason:] The magnetic moment is the amount of torque produced in a magnetic field. This is expressed in terms of the constant known as Bohr magneton.

Answer: a [Reason:] Bohr magneton is defined as that constant which is used to express the magnetic moment of an electron. It is mathematically defined by . It has a constant value of 9.273 * 10^-24 A m² in case of SI units and 9.273 * 10^-21 A m² in case of CGS units.

Answer: d [Reason:] In electromagnetism, susceptibility is defined as a measure which is used to identify whether a material is attracted to or repelled on the application of a magnetic field. It is denoted by X and is mathematically defined as.

Answer: a [Reason:] Diamagnetism is caused due to the modifications of motion of electrons which produces an opposing magnetic field. The magnetic lines of force are repelled, which results in weak force and low susceptibility. Copper, mercury, and gold are common examples of diamagnetic materials.

Answer: c [Reason:] Superconductors are considered as perfect diamagnets due to their ability to eject magnetic force in all directions. This principle is based on the well known Meissner effect. Superconductors have a susceptibility of -1 * 105.

Answer: c [Reason:] The phenomenon by which the magnetic moments of atoms of a material get aligned in the direction of the magnetic field is known as paramagnetism. This force is usually small, thereby producing a weak effect.

Answer: b [Reason:] Curie temperature is defined as that temperature at which materials lose their permanent magnetic properties. In other words, a transition from ferromagnetic state to paramagnetic phase occurs. This is otherwise also known as Curie point, named after Pierre Curie.

Answer: b [Reason:] Neel temperature is defined as that temperature at which materials lose their magnetic ordering due to a large thermal energy. In other words, a transition from anti-ferromagnetic state to paramagnetic phase occurs. This is otherwise also known as magnetic ordering temperature and is named after Louis Neel.