Answer: a [Reason:] De Broglie’s wavelength λ=h⁄mv. λ represents wavelength, h is Plancks constant, m represent mass and v represents velocity.

Answer: a [Reason:] Conductivity increases with increase in mean free path of crystal. Conductivity is inversely proportional to resistance of material.

Answer: d [Reason:] Silver has lowest conductivity so resistivity is equal to 10^-9 ohm-m.

Answer: b [Reason:] Iron has medium conductivity so resistivity is equal to 10^-6 ohm-m. Silver has lowest conductivity.

Answer: a [Reason:] Bismuth has low conductivity so resistivity is equal to 10^-4. Silver has lowest conductivity.

Answer: d [Reason:] For insulator Electric gap is very large and is generally greater than 3eV. It requires large energy to cross electron along the gap.

Answer: b [Reason:] For conductors Electric gap is very small and is generally smaller than 1eV. For insulator Electric gap is very large and is generally greater than 3eV.

Answer: a [Reason:] A = 3.14*d²/4 and resistivity = R*A/l, where ‘a’ is the area of cross section of wire and ρ is specific resistance.

Answer: b [Reason:] A = 3.14*d²/4 and resistivity = R*A/l, where ‘a’ is the area of cross section of wire and ρ is specific resistance.

Answer: b [Reason:] Semiconductor have negative temperature coefficient of resistance. There resistance increases with decrease in temprature.

Answer: d [Reason:] Electro chemical machining is an un-conventional machining process used for large material removal from the surface using electricity generated due to chemical reactions.

Answer: b [Reason:] Milling is a conventional machining process used for material removal from the surface.

Answer: b [Reason:] Sparks are generated in EDM, by using high voltage current, for proper erosion of material.

Answer: a [Reason:] Tool is very near to work piece but does not touch it in ECM.

Answer: a [Reason:] In ECM, erosion of metal takes place as reverse process of electroplating.

Answer: d [Reason:] Wood is a bad conductor of electricity and hence cannot be machined using electro chemical machining.

Answer: a [Reason:] Iron is a good conductor of electricity and hence can be machined using electro chemical machining.

Answer: c [Reason:] Electrode gap in electro chemical machining is generally ranges from 0.1 mm to 0.2 mm.

Answer: c [Reason:] Electrolytes used in ECM must have high electrical conductivity.

Answer: d [Reason:] Electrolyte provide reactive environment for chemical reactions to takes place.

Answer: d [Reason:] The various methods of mechanical surface treatments includes
a) shot peening
b) laser shot peening
c) water jet peening
d) ultrasonic peening
e) roller burnishing
f) explosive hardening

Answer: b [Reason:] In mechanical plating (also called mechanical coating, impact plating, or peen plating), fine metal particles are compacted over the workpiece surfaces by glass, ceramic, or porcelain beads that are propelled by rotary means (such as tumbling).

Answer: d [Reason:] Thermal spraying is a series of processes in which coatings of various metals, alloys, carbides, ceramics, and polymers are applied to metal surfaces by a spray gun with a stream heated by an oxyfuel flame, an electric arc, or a plasma arc.

Answer: a [Reason:] The oxyfuel flame melts the wire and deposits it on the surface. The bond is of medium strength, and the process is relatively inexpensive.

Answer: b [Reason:] Conversion coating, also called chemical-reaction priming, is the process of producing a coating that forms on metal surfaces as a result of chemical or electrochemical reactions. Various metals (particularly steel, aluminum, and zinc) can be conversion coated. Oxides that naturally form on their surfaces represent a form of conversion coating.

Answer: d [Reason:] Paints generally are classified as
a) Enamels: Produce a smooth coat with a glossy or semi-glossy appearance.
b) Lacquers: Form a film by evaporation of a solvent.
c)Water-based paints: Applied easily, but have a porous surface and absorb water, making them more difficult to clean than the first two types.

Answer: d

Answer: d [Reason:] Chemical cleaning usually involves the removal of oil and grease from surfaces. The operation consists of one or more of the following processes:
a) Solution: The soil dissolves in the cleaning solution.
b) Saponification: A chemical reaction converts animal or vegetable oils into a soap that is soluble in water.
c) Emulsification: The cleaning solution reacts with the soil or lubricant deposits and forms an emulsion; the soil and the emulsifier then become suspended in the emulsion.
d) Dispersion: The concentration of soil on the surface is decreased by surface active elements in the cleaning solution.
e) Aggregation: Lubricants are removed from the surface by various agents in the cleanser and are collected as large dirt particles.

Answer: d [Reason:] Common cleaning fluids used in conjunction with electrochemical processes for more effective cleaning include the following:
a) Alkaline solutions: A complex combination of water-soluble chemicals, alkaline solutions are the least expensive and most widely used cleaning fluids in manufacturing operations. Small parts may be cleaned in rotating drums or barrels. Most parts are cleaned on continuous conveyors by spraying them with the solution and rinsing them with water.
b) Emulsions: Emulsions generally consist of kerosene and oil-in-water and various types of emulsifiers.
c) Solvents: Typically petroleum solvents, chlorinated hydrocarbons, and mineral spirits, solvents generally are used for short runs. Fire and toxicity are major hazards.
d) Hot vapors: Chlorinated solvents can be used to remove oil, grease, and wax. The solvent is boiled in a container and then condensed. This hot-vapor process is simple, and the cleaned parts are dry.
e) Acids, salts, and mixtures of organic compounds: These are effective in cleaning parts covered with heavy paste or oily deposits and rust.

Answer: d [Reason:] Type of laser surface treatments are
a) heating
b) melting
c) vaporization
d) peening

Answer: c [Reason:] The evaporative-pattern casting process uses a polystyrene pattern, which evaporates upon contact with molten metal to form a cavity for the casting. This process is also known as lost-foam casting and falls under the trade name full-mold process.

Answer: a [Reason:] The investment-casting process, also called the lost-wax process, was first used during the period from 4000 to 3000 B.C. Typical parts made are components for office equipment, as well as mechanical components such as gears, cams, valves, and ratchets.

Answer: b [Reason:] In permanent-mold casting (also called hard-mold casting), two halves of a mold are made from materials with high resistance to erosion and thermal fatigue, such as cast iron, steel, bronze, graphite, or refractory metal alloys.

Answer: a [Reason:] In order to increase the life of permanent molds, the surfaces of the mold cavity usually are coated with a refractory slurry (such as sodium silicate and clay) or sprayed with graphite every few castings. These coatings also serve as parting agents and as thermal barriers, thus controlling the rate of cooling of the casting.

Answer: a [Reason:] Vacuum casting is an alternative to investment, shell-mold, and green-sand casting and is suitable particularly for thin-walled (0.75 mm) complex shapes with uniform properties.

Answer: b [Reason:] Hollow castings with thin walls can be made by permanent-mold casting using this principle: a process called slush casting. This process is suitable for small production runs and generally is used for making ornamental and decorative objects (such as lamp bases and stems) and toys from low-melting-point metals such as zinc, tin, and lead alloys.

Answer: c [Reason:] In pressure casting (also called pressure pouring or lou/-pressure casting), the molten metal is forced upward by gas pressure into a graphite or metal mold.

Answer: a [Reason:] Composite molds are made of two or more different materials and are used in shell molding and other casting processes. They generally are employed in casting complex shapes, such as impellers for turbines.

Answer: b [Reason:] In rheocasting, the metal is heated to just above its solidus temperature and poured into a vessel to cool it down to the semisolid state. The slurry is then mixed and delivered to the mold or die.

Answer: d [Reason:] The advantages of semisolid metal forming over die casting are
a) the structures developed are homogeneous, with uniform properties, lower porosity, and high strength
b) both thin and thick parts can be made
c) casting as well as wrought alloys can be used
d) parts subsequently can be heat treated,
e) the lower superheat results in shorter cycle times.
However, material and overall costs are higher than those for die casting.

Answer: d [Reason:] Typical applications of sand casting include machine bases, large turbine impellers, propellers, plumbing fixtures, and a wide variety of other products and components.

Answer: d [Reason:] Basically, sand casting consists of
a) placing a pattern (having the shape of the desired casting) in sand to make an imprint,
b) incorporating a gating system,
c) removing the pattern and filling the mold cavity with molten metal,
d) allowing the metal to cool until it solidifies,
e) breaking away the sand mold, and
f) removing the casting

Answer: b [Reason:] Patterns are used to mold the sand mixture into the shape of the casting and may be made of wood, plastic, or metal. The selection of a pattern material depends on the size and shape of the casting, the dimensional accuracy and the quantity of castings required, and the molding process.

Answer: a [Reason:] Sandslingers fill the flask uniformly with sand under a high-pressure stream, they are used to fill large flasks and are operated typically by machine.

Answer: b [Reason:] In impact molding, the sand is compacted by a controlled explosion or instantaneous release of compressed gases whine in vacuum molding the pattern is covered tightly with a thin sheet of plastic.

Answer: a [Reason:] In vacuum molding (also known as the V process), the pattern is covered tightly with a thin sheet of plastic while in impact molding, the sand is compacted by a controlled explosion or instantaneous release of compressed gases.

Answer: d [Reason:] Shell-molding applications include small mechanical parts requiring high precision, such as gear housings, cylinder heads, and connecting rods. The process also is used widely in producing high-precision molding cores.

Answer: c [Reason:] In the plaster-molding process, the mold is made of plaster of paris (gypsum or calcium sulfate) with the addition of tale and silica flour to improve strength and to control the time required for the plaster to set.

Answer: b [Reason:] Typical parts made are impellers, cutters for machining operations, dies for metalworking, and molds for making plastic and rubber Components. Parts weighing as much as 700 kg have been cast by this process.

Answer: b [Reason:] In the plaster-molding process, castings have a good surface finish with fine details. Because plaster molds have lower thermal conductivity than other mold materials, the castings cool slowly, and thus a more uniform grain structure is obtained with less warpage.