Latest Electrical Engineering Materials Questions and Answers 1. The converse of hardness is known as (a) malleabilit (b) toughness (c) softness (d) none of the above Ans! c ". #n which of the following factors does the resistivit of a material de$end % (a) &esistance of the conductor (b) Area of the conductor section (c) Length of the conductor (d) All of the above Ans! d '. is a negativel negativel charged $article $resent in an atom. (a) roton (b) eutron (c) Electron (d) one of the above Ans! c *. The formula ++++ determines the number of electrons that can be accommodated in an level. (a) "n" (,) *n" (c) "n' (d) *ns Ans! a -. The tin block formed b the arrangement of a small grou$ of atoms is called the (a) unit cell (b) s$ace lattice (c) either (a) or (b) (d) none of the above Ans! a ,. The coordination coordination number number of a sim$le cubic structure structure is (a) " (b) * (c) , (d) / Ans! c 0. The covalen covalentt bond bond is formed b (a) transfer of electrons between atoms (b) sharing of electrons between atoms (e) sharing of variable number of electrons b a variable variable number of atoms (d) none of the above Ans! b /. A $erfect conductor has (a) ero conductivi conductivit t (b) unit conductivit (c) infinite conductivit (d) none of the above Ans! c 2. The metal having the lowest tem$erature coefficient coefficient of resistance is (a) gold (b) co$$er (c) aluminium (d) kanthal Ans! a 13. 4ommonl used conducting materials are (a) co$$er (b) aluminium
(c) both (a) and (b) (d) co$$er and silver (e) $latinum and gold Ans! c 11. 5hich of the following materials is $referred for transmitting electrical energ over long distance % (a) 4o$$er (b) Aluminium (c) 6teel reinforced co$$er (d) 6teel reinforced aluminium Ans! d 1". The kinetic energ of a bounded electron is (a) less than that of unbounded electron (,) greater than that of unbounded electron (c) e7ual to that of unbounded electron (d) infinite (e) none of the above Ans! a 1'. A highl conductive material must have (a) highest conductivit (b) lowest tem$erature coefficient (c) good mechanical strength (d) good corrosion resistance (e) eas solderable and drawable 7ualit (f) all of the above Ans! f 1*. The conductivit of a conductor can be increased b (a) decreasing its tem$erature (b) increasing its tem$erature (c) decreasing its vibration (d) increasing its vibration Ans! a 1-. 6u$erconductivit is observed for (a) infrared fre7uencies (b) d.c. and low fre7uenc (c) a.c. and high fre7uenc (d) fre7uencies having no effect (e) none of the above Ans! b 1,. The su$erconductivit is due to (a) the crstal structure having no atomic vibration at 389 (b) all electrons interact in the su$erconducting state (c) the electrons :um$ into nucleus at 389 (d) none of the above Ans! a 10. The value of critical f ield below the transition tem$erature will (a) increase (b) decrease (c) remain unchanged (d) an of the above Ans! a 1/. ;n a su$erconductor the value of critical densit de$ends u$on (a) magnetic field strength (b) tem$erature (c) either (a) or (b) (d) both (a) and (b) Ans! d 12. 6u$erconductors are becoming $o$ular for use in (a) generating ver strong magnetic field (b) manufacture of bubble memories (c) generating electrostatic field (d) generating regions free from magnetic field Ans! a
"3.
9 Ans! c "0. ? increasing im$urit content in the metal allo the residual resistivit alwas (a) decreases (b) increases (c) remains constant (d) becomes tem$erature inde$endent Ans! b "/. The structure sensitive $ro$ert of a su$er conductor is (a) critical magnetic field (b) transition tem$erature (c) critical current densit (d) none of the above Ans! c "2. At transition tem$erature the value of critical field is (a) ero (,) negative real value (c) $ositive real value (d) com$le@ value Ans! a
'3. 5hich of the following variet of co$$er has the best conductivit % (a) ;nduction hardened co$$er (b)
*3. #verhead tele$hone wires are made of (a) aluminium (b) steel (c) A46& conductors (d) co$$er Ans! b *1. ++++++ is an e@am$le of $ieoelectric material. (a) lass (b) Quart (c) 4orrundum (d) eo$rene Ans! b *". +++++ is the main constituent of glass (a) Ce"3' (b) 6i3" (c) A;"#' (d) ?"#' Ans! b *'. A good electric contact material should have all of the following $ro$erties e@ce$t (a) high resistivit (b) high resistance to corrosion (c) good thermal conductivit (d) high melting $oint Ans! a **. Most of the common metals have +++++ structure. (a) linear (b) he@agonal (c) orthorhombic (d) cubic Ans! d *-. 5hich of the following affect greatl the resistivit of electrical conductors % (a) 4om$osition (b) ressure (c) 6ie (d) Tem$erature Ans! a *,. Thermonic emission occurs in (a) vacuum tubes (b) co$$er conductors (c) ferrite cores (d) transistors Ans! a *0. +++++ is a hard solder. (a) Tinlead (,) Tinsilverlead (c) 4o$$erinc (d) one of the above Ans! c */. Addition of 3.' to *.-D silicon to iron +++++ the electrical resistivit of iron. (a) increases (b) decreases (c) does not change Ans! a *2. 6u$er conductivit can be destroed b (a) adding im$urities (b) reducing tem$eratures (c) a$$lication of magnetic field (d) an of the above Ans! c -3. (a)
onlinear resistors $roduce harmonic distortion
(b) follows #hm>s law at low tem$eratures onl (c) result in nonuniform heating (d) none of the above Ans! a -1. A carbon resistor contains (a) carbon crstals (b) solid carbon granules (c) $ulveried coal (d) finel divided carbon black. Ans! d -". 5hich of the following materials does not have covalent bonds % (a) #rganic $olmers (b) 6ilicon (c) Metals Ans! c -'. ;n gra$hiteB bonding is (a) covalent (b) metallic (c) ander 5aals (d) ander 5aals and covalent Ans! d -*. Total number of crstal sstems is (a) " (b) * (c) 0 (d) 1" Ans! c --. The number of atoms $er unit cell in ?.4.4. structure is (a) 1 (b) " (c) * (d) / Ans! b -,. The conductivit of a metal is determined b (a) the electronic concentration and the mobilit of the free electrons (,) the number of valence electrons $er atom (c) either (a) or (b) (d) none of the above Ans! a -0. The resistivit of a metal is a function of tem$erature because (a) the am$litude of vibration of the atoms varies with tem$erature (b) the electron densit varies with tem$erature (c) the electron gas densit varies with tem$erature Ans! a -/. ;n a crstalB an atom vibrates at a fre7uenc determined b (a) the heat content of the crstal (b) the tem$erature of the crstal (c) the stiffness of the bonds it makes with neighbors Ans! c -2. =ue to which of the following reasons aluminium does not corrode in atmos$here % (a) Aluminium is a noble metal (b) Atmos$heric o@gen can onl diffuse ver slowl through the o@ide laer which is formed on the surface of aluminium (c) o reaction with o@gen occurs ft An of the above Ans! b ,3. The im$urit atoms is semiconductors (a) in:ect more charge carriers (,) reduce the energ ga$ (c) increase the kinetic energ of valence electrons (d) all of the above Ans! b
,1. 5hich of the following material is not a semiconductor % (a) 6ilica (b) ermanium (c) 6elenium (d) alliumarsenide Ans! a ,". 4arbon resistors are used e@tensivel because the are (a) eas to make (b) com$act (c) ine@$ensive (d) all of the above reasons Ans! d ,'. 4arbon rods are used in wet and dr cells because (a) carbon rod serves as conductor (b) carbon can resist the attack of batter acid (c) both (a) and (b) (d) either (a) or (b) Ans! c ,*. =ue to which of the following factors the brush wear rate is altered % (a) 6$eed of the machine (b) 4ontact $ressure (c) 6urface conditions of brush and commutator (d) E@cessive s$arking (e) All of the above Ans! e ,-. 5hich of the following are nonconductors of electricit% (a) onmetal solids e@ce$t carbon (b) Air and most other gases (c) ure water and li7uids in general e@ce$t mercur (d) All of the above Ans! d ,,. 4arbon bearings are used under which of the following conditions % (a) 5here lubrication is difficult or im$ossible (b) 5here corrosive chemical action e@ists (c) 5here high tem$erature e@ists (d) All of the above Ans! d ,0. 5hich of the following high resistance materials has the highest o$erating tem$erature % (a) 9anthal (b) Manganin (c) ichrome (d) Eureka Ans! a ,/. 6teel wire is used as (a) overhead tele$hone wire (b) earth wire (c) core wire of A46& (d) all of the above Ans! d ,2. Low resistivit materials are used in (a) transformerB motor and generator windings (b) transmission and distribution lines (c) house wiring (d) all above a$$lications Ans! d 03. latinum is used in (a) electrical contacts (b) thermocou$le (c) heating element in high tem$erature furnace (d) grids of s$ecial $ur$ose vacuum tubes (e) all of the above
Ans! e 01. 5hich of the following is an advantage of stranded conductor over e7uivalent single conductor % (a) Less liabilit to kink (b) reater fle@ibilit (c) Less liabilit to break (d) All of the above Ans! d 0". =ue to which of the following reasons co$$er and aluminium are not used for heating elements % (a) ?oth have great tendenc for o@idation (b) ?oth have low melting $oint (c) er large length of wires will be re7uired (d) All of the above Ans! d 0'. 4o$$erB even though costlB finds use in the windings of electrical machines because (a) co$$er $oints offer low contact resistance (b) co$$er can be easil soldered and welded (e) co$$er windings are less bulk and the machines become com$act (d) all of the above Ans! d 0*. 5hich of the following materials is used for making coils of standard resistances % (a) 4o$$er (b) ichrome (c) latinum (d) Manganin Ans! d 0-. 6ubstances whose s$ecific resistance abru$tl decreases at ver low tem$erature are called (a) insulators (b) conductors (c) semiconductors (d) su$erconductors Ans! d 0,. 5hich of the following materials is the best conductor of electricit % (a) Tungsten (b) Aluminium (c) 4o$$er (d) 4arbon Ans! c 00. is the $ro$ert of absorbing moisture from atmos$here. (a) 6olubilit (b) iscosit (c) orosit (d) <grosco$icit Ans! d 0/. Thermocou$les are mainl used for the measurement of (a) tem$erature (b) resistance (c) edd currents (d) cou$ling coefficient Ans! a 02. =ue to which of the following factB in ;ndiaB aluminium is re$lacing co$$er % (a) Aluminium is more ductile and malleable than co$$er (,) Aluminium is available in $lentB chea$er and lighter than co$$er (c) Aluminium has lower resistivit than that of co$$er (d) Aluminium has less tem$erature coefficient than co$$er Ans! b /3. The conduction of electricitB in semiconductorsB takes $lace due to movement of (a) $ositive ions onl (b) negative ions onl (c) $ositive and negative ions (d) electrons and holes Ans! d
/1. 5hich of the following is a semiconductor material % (a) hos$horous (b) &ubber (c) 6ilicon (d) Aluminium Ans! c /". 6elenium is +++++ semiconductor. (a) e@trnisic (b) intmisic (c) t$e (d) t$e Ans! b /'. ++++++++ has the best dam$ing $ro$erties. (a) =iamond (b) s law it is known as (a) nonlinear conductor (b) reverse conductor (c) badconductor (d) nonconductor Ans! a /,. 6$ark $lug makes use of which of the following materials for insulation % (a) orcelain (b) 6late (c) Asbestos (d) lass Ans! a /0. The forbidden ga$ in an insulator is (a) large (b) small (c) nil (d) an of the above Ans! a //. 5hich of the following factors affect resistivit of metals % (a) Age hardening (b) Alloing (c) Tem$erature (d) 4old work (e) All of the above Ans! e /2. Effect of moisture on the insulating materials is to (a) decrease dielectric constant (b) decrease dielectric strength (c) decrease insulation resistance (d) increase dielectric loss (e) all of the above Ans! e 23. 6urface resistance of an insulating material is reduced due to the (a) smok and dirt atmos$here (b) humidit in the atmos$here (c) both (a) and (b) (d) neither (a) nor (b)
Ans! c 21. 6u$erconducting metal in su$er conducting state has relative $ermeabilit of (a) ero (b) one (c) negative (d) more than one Ans! a 2". ;n conductors conduction of electricit takes $lace due to movement of (a) electrons onl (b) $ositive ions onl (c) negative ions onl (d) $ositive and negative ions (e) none of the above Ans! a 2'. The carbon $ercentage is least in (a) low carbon steel (b) wrought iron (c) cast iron (d) malleable iron Ans! b 2*. Cor a $articular material the
