Recent questions tagged engineering-materials

Description : Fire refining process is employed in case of (A) Tin (B) Copper (C) Zinc (D) Aluminium

Last Answer : (B) Copper

Description : The following type of bonding is strongly directional in solids. (A) Vander Waal's (B) Ionic (C) Metallic (D) Covalent

Last Answer : D) Covalent

Description : What is a modular system? List the important properties of a modular system.

Last Answer : Ans: A modular system consists of well defined manageable units to well defined interfaces among them. Desirable properties are Each module is a well defined subsystem useful to others Each module ... modules Modules should be easier to use than build Modules should have a simple interface

Description : State the functions of a fuse. Mention the desirable properties of fuse materials.

Last Answer : Ans: Fuse is a protective device, which consists of a thin wire or strip. This wire or strip is placed with the circuit it has to protect, so that the circuit-current flows through it. When ... silver and silver alloys are used of lower ratings. Copper alloys are used in fuses of higher ratings.

Description : Give four examples of natural insulating materials.

Last Answer : Ans: Examples of the natural insulating materials are cotton, rubber, wood, mica.

Description : Classify plastic materials into two categories, describe their important properties and give two examples of each.

Last Answer : Ans: Plastic materials can be classified into thermoplastic and thermosetting plastics. Thermoplastic materials:- The properties of these plastic materials do not change considerably if they are melted ... forming elastic threads and films. Examples are Phenol formaldehyde (Bakelite), Epoxy resins.

Description : Ferroelectric materials are characterised by (A) Very high degree of polarisation. (B) A sharp dependence of polarisation on temperature. (C) Non-linear dependence of the charge Q on the applied voltage. (D) All the above.

Last Answer : (D) All the above.

Description : Tick of the property, which is different from the group (A) Ductility. (B) Resistivity. (C) Tensile strength. (D) Hardness.

Last Answer : (B) Resistivity

Description : Tick off the material, which is different from the group (A) Constantan. (B) Manganin. (C) Nichrome. (D) Brass.

Last Answer : (D) Brass.

Description : Semi-conductors have ________ temperature coefficient of resistance. (A) Negative (B) Positive (C) Both positive and negative (D) None of the above

Last Answer : (A) Negative

Description : Atoms with four valence electrons are good conductors. (A) True (B) False

Last Answer : (B) False

Description : Hysteresis loss least depends on (A) Frequency. (B) Magnetic field intensity. (C) Volume of the material. (D) Grain orientation of material.

Last Answer : (D) Grain orientation of material.

Description : Insulators have (A) A full valence band. (B) An empty conduction band. (C) A large energy gap. (D) All the above.

Last Answer : (C) A large energy gap.

Description : Paper is hygroscopic and absorbent. (A) True (B) False

Last Answer : (A) True

Description : In a ferromagnetic material the state of flux density is as follows when external magnetic field is applied to it. (A) Increased (B) Decreased (C) Remains unchanged (D) Becomes zero

Last Answer : (C) Remains unchanged

Description : Magnetic materials (A) provide path to magnetic flux. (B) are good insulators. (C) are semiconductors. (D) None.

Last Answer : (A) provide path to magnetic flux.

Description : Addition of trivalent impurity to a semiconductor creates many (A) holes. (B) free electrons. (C) valance electrons. (D) bound electrons.

Last Answer : (B) free electrons.

Description : Hall effect is associated with (A) Conductors. (B) Semiconductors. (C) Thermistors. (D) Solders.

Last Answer : (B) Semiconductors.

Description : Hard magnetic materials are used for making (A) Permanent magnets. (B) Temporary magnets. (C) Conductors. (D) Insulator.

Last Answer : (A) Permanent magnets.

Description : Example of high resistivity material is (A) Nichrome (B) Silver (C) Gold (D) Copper

Last Answer : (A) Nichrome

Description : A transistor has (A) One p-n junction. (B) Two p-n junction. (C) Four p-n junction. (D) Five p-n junction.

Last Answer : (B) Two p-n junction.

Description : Bronze is an alloy of (A) Copper and Tin. (B) Copper and Steel. (C) Copper and Mercury. (D) Copper and Aluminium.

Last Answer : (A) Copper and Tin.

Description : Which of the following material has the highest melting point (A) Copper. (B) Aluminium. (C) Tungsten. (D) Gold.

Last Answer : (C) Tungsten.

Description : Number of Terminals in a MOSFET are (A) Two (B) Three (C) Four (D) Five

Last Answer : (B) Three

Description : When a semiconductor is doped with a P-type impurity, each impurity atom will (A) acquire negative charge. (B) acquire positive charge. (C) remain electrically neutral. (D) give away one electron.

Last Answer : (A) acquire negative charge.

Description : The conductivity of an extrinsic semiconductor (A) decreases with temperature. (B) increases with temperature. (C) remains constant with temperature. (D) decreases and then increases with temperature.

Last Answer : (B) increases with temperature.

Description : P-N junction is (A) a rectifier. (B) an amplifier. (C) an Oscillator. (D) a Coupler.

Last Answer : (A) a rectifier.

Description : What is the type of bonding in silicon? (A) Ionic. (B) Covalent. (C) Metallic. (D) Ionic + Metallic

Last Answer : (B) Covalent.

Description : Micanite is a form of (A) Built up mica. (B) Hydrated potassium aluminium silicate. (C) Magnesium mica. (D) Calcium mica.

Last Answer : (A) Built up mica.

Description : The main constituents of glass is (A) SiO2 (B) B2O3 (C) Al2O3 (D) Cr2O3

Last Answer : (A) SiO2

Description : Hard ferrites are used for making (A) Transformer cores. (B) Electrical machinery. (C) High frequency equipment. (D) Light weight permanent magnets.

Last Answer : (D) Light weight permanent magnets.

Description : Aluminium is (A) Silvery white in colour. (B) Yellow in colour. (C) Reddish in colour. (D) Pale yellow in colour.

Last Answer : (A) Silvery white in colour.

Description : The percentage of carbon in mild steel is (A) 0.08 to 0.3 % (B) 0.5 to 1.4 % (D) 2.35 % (D) 0.5 %

Last Answer : (A) 0.08 to 0.3 %

Description : The most malleable, ductile low resistivity material is (A) Copper. (B) Aluminium. (C) Silver. (D) Iron.

Last Answer : (C) Silver.

Description : The heating elements of electric irons are made of (A) Copper. (B) Nichrome. (C) Constantan. (D) Aluminium.

Last Answer : (B) Nichrome.

Description : Barrier potential in a P-N junction is caused by (A) Thermally generated electrons and holes. (B) Diffusion of majority carriers across the junction. (C) Migration of minority carriers across the junction. (D) Flow of drift current.

Last Answer : (B) Diffusion of majority carriers across the junction.

Description : In order to obtain p-type germanium it should be doped with a (A) Trivalent impurity. (B) Tetravalent impurity. (C) Pentavalent impurity. (D) Any of the above will do.

Last Answer : (A) Trivalent impurity.

Description : Plastics are (A) Good conductors of heat. (B) Good conductors of electricity. (C) Bad conductors of electricity. (D) High density.

Last Answer : (C) Bad conductors of electricity.

Description : For silicon the forbidden gap is (A) 1.1ev. (B) 0.25ev. (C) 0.5ev. (D) 0.7ev.

Last Answer : (A) 1.1ev.

Description : Transformer cores are laminated with (A) Low carbon steel. (B) Silicon sheet steel. (C) Nickel alloy steel. (D) Chromium sheet steel.

Last Answer : (B) Silicon sheet steel.

Description : A ferrite core has less eddy current loss than an iron core because ferrites have (A) High resistance. (B) Low resistance. (C) Low permeability. (D) High hysteresis.

Last Answer : (A) High resistance.

Description : The conductivity of copper is less than that of silver by (A) 5 – 10 %. (B) 50 – 60 %. (C) 80 – 90 %. (D) 20 – 30 %.

Last Answer : (A) 5 – 10 %.

Description : Mica is a (A) Dielectric material. (B) Insulating material. (C) Magnetic material. (D) Both insulating and dielectric material.

Last Answer : (D) Both insulating and dielectric material.

Description : Resistivity of conductors is most affected by (A) composition. (B) temperature. (C) pressure. (D) current.

Last Answer : (B) temperature.

Description : The dielectric strength of transformer oil should be (A) 100 V. (B) 5 KV. (C) 30 KV. (D) 132 KV.

Last Answer : (C) 30 KV.

Description : For germanium the forbidden gap is (A) 0.15ev. (B) 0.25ev. (C) 0.5ev. (D) 0.7ev.

Last Answer : (D) 0.7ev.

Description : Copper is completely miscible with (A) nickel. (B) gold. (C) hydrogen. (D) lead.

Last Answer : (B) gold.

Description : In p-type semiconductor the majority carriers are (A) holes. (B) electrons. (C) positive ions. (D) negative ions.

Last Answer : (A) holes.

Description : A pure semiconductor under ordinary conditions behaves like (A) a conductor. (B) an insulator. (C) a magnetic material. (D) a ferro-electric material.

Last Answer : (B) an insulator.

Description : Eddy current loss is proportional to the (A) frequency. (B) square of the frequency. (C) cube of the frequency. (D) square-root of the frequency.

Last Answer : (B) square of the frequency.