Basic Electrical Engineering que_2

25, TRIBHUVAN UNIVER.SITY

INSTITUTE OF ENGINEERING

Examination Comtrol Division Programme
Year / Part
3il?4 Askwim

Engineering (EE40t.

candidates are required to give their answers in their own words as far as practicable.
questians.
Attempt 4!!

The figures in the margin indicate {utt fuIarks.

necess&ry.-Assume suitable data if

1' a) mwehtahot ddofoyr ocuonmveeratirngbypriadcetiaclaal nvcol l.tpargaectsicoaulrcveolitnatglecuarnednct usroruerncte source? Explain the
and vice versa.
b) mtiAneams6tteap0reniarwtal-otauisftrte,s02w.o04if0t0c4thhv5eion/ifgknil.acomaNned.netTsihsce2e0tne0trj0nl^opTec.ria.Dlttuelrtaeemrmcpoineiseffisctwhieertnccthueorrdfenroetnstaiaskttae2nn0cboeyco.thfTethhelaemofpiplearamatteitnhnget tsl

c) jDsAoueinptceepirrdlcmieuiidnniteapcttaoh6rneat0alvlvieanlliuanisengdcotohfintrfenoieseucrrftteohesdurinseitdsnoi.srtssthaeanwritceietsphoawrewnisdtehisrthtadaeinfstocsouieprlsltahtplezroderw2siies,srtla1gn2gcCeI.arnTedshies3ta6wnfh)ctoehrleeeissgpcrei3orcc6utuwipvi.aet tlitys. L1v6.ll
a)
Make comparison kbre between series and parallel circuit. t5l
disip;;;2.
14]
b) For the circuit shown in belorv figure, determine the resistance between points A and
B using star / delta transformation theorem. t6l

c) Find all branch currents in the given circuit by usi'g mesh current method. 161

3. a) Using Nodal analysis, determine currents in each branch of the network shorm in l8l

below figure. Also find the total power loss in the network.

10C) 20a

b) Find the value af Resistance 'R' to have maximum power tra.nsfer in the circuit as l8l
shown in beiow figure. Als* obtain the amount of maximuri pov/er.

4. a) Two inductances Lr and L2 are connected in parallel. Derive the relation showing the t4l

equivaient inductance of the combination when mutual flux helps the individual flux. i4l
what will be the equivalent inductance of the combination when mutual flux opposes t8l
the individual flux?

b) Tw.o alte/r\nating currents represented by the equations i1 = Tsinwt and
i"" =10sin[[o:t+2I )I are fed into a cornmon conductor. Find the equation for the

resultant current and its RMS value.

c) Belorv Figure shows a series parallel circuit. Find:

(i) totai impedance
(ii) curent drawn f,rom the circuit
(iii)voltage across the parallel branches
(iv)cunent flowing ttrough each parallel branch
(v) powel factor
(vi)Active, reactive and apparent power

Also, draw the phasor diagram of the circuit.

R::20() Ci: l00pF

200V. 50 Hz

a;il;"5. a) (csAia)uppfulaupncoriirytryae' nsT(ccihiee)en0tto.p9loab5mwetapecgrotgnaciknnoeegnsc.staeydcllucinrrrepbnaytraotlhrfee0l .l*7ai5imr4,pwtrirsrr"e8nla0mcowpnantouec.itmedpraocvreosthsetahp2eo4wv0aeyrr,u5fe0acHot2of rtaht.oec l6l
ffi?*ffi':gb) balanced three phase loads are connected to a 415 v, three phase, ibur t4l

lil 19q kVA at 0.7 power factor lagging t6l
IYl"(liiiiil):5?0 0.65 power a.to, r"ii'ioi
kW at
unity power factor

c) pPcoarowlcveuerlaitnhtearnt(aesa)usmtuhreeomtfoettanhtreloorfeaadpdoiinwngkirsvoAorf:-(tbpw)hotuhsewealilnitrlecmuceiutrrlrsbeynits2(ewc)qautthtamel ectotoemrthbmeinetetohdtoadpr.otwhreerefapchtaosre
t+*

ll Level BE Full,Marks 80
Fass Marks
i--i S TITUTE OF E,NGINE.ERN G Programme BEL, BEX. BCT', Time -):
Year / Part BAME. BIE. B. Asri" 3 hrs.
E ramination Control Division
TII
2074 Chaitra

- Basic Electrical f,ngineering (EE40li

, Candidates are requirecl to give their answers in their orvn words as far as piacticabie.
, -itrempt All qttestians"

Ttte /igures in the margin indicate Full *Iarks.

" .issutne suitable data if necessurr.

. a I \\tat is source transformation? Erpiain with the help of an example. t4j
)r A coil of stranded oopper w.ire having a resistance of l2O at 25oC is embedded in the
t6l
core of a large transforrner suppiied at 230 V. Atter the transfomer has been in t6l
seryice for several hours, the resistance of the coil is fr-runi to be 13,4 A. What is the
iemperature of the core? Also finri the power ratirig of the resistance. Assurne

temperature coefficient of lvire as 0.00125,/oC at 15oC.

r! Find V*u in the following circuit diagrarn.

r-

8r'

t l5l

Lise loop curent rnethod to calculitte the current through the 2Q resistanee for ther

netrvork shown belorv.

12v

r) Solye the given ner*ork n,ith nodal analysis to find voltage drop otr 8Q resisior. i6t
[4]
I O' '' h'u

4.4

YI\*

lil,o 1 6Q: ;( ,},, A
i', n
7

It

I

c) statc antl explain Norton's theorern rvith stiitable exampie.

3. a) Find power dissipated in 3 f) resistor using Norlon's theorem t6l

20 i I 4f) 'lr-

20v 5 -{t,"'Z (,110 A 3r)

b) Calculate the value of 'R' such that maximum power will be absorbed by it in the i6l

given circuit. 5f) 10C)

c) Whal is inductance? Derive the expression for two inductances in series, wi& mutual t4l
flux aiding each other. t4l

4. a) Calculate the average (half period) value and rms value of the naveforrn shoqrt

below.

b) rAicneinsrsctiasautnliatttena(rcninie.iao)tui2vnso0gltocasugoareurnrecddferitoionpudfroueancmtprafeonsvci*s=e"to2,0r0f0.aa1sncidtnHoirn(3rd(e1uisi4cjptt)oearvccottaiilvvntseedlyir(sei.vaaD)cpectpiotvleineersdmtamtnloncdgtaap(pph0rapasaceotexircnpadrteliapscgsooriraoi*lmn'esr'ffitooohrrf t_61

above circuit. l6l
c) Find cu:rent flowing in each branches of the following circuit:

5. a) A 400V, 50 H3, 3 phase induction motor takes 60 KW power from supply mains at 18]

0.8 power factor lagging. Calculate the capacitance per phase and KVAR rating per
phase of capacitor in order to improve the power factor to 0.9 lagging using (i) star

connectedcapacitorbank and (ii) Delta connected capacitorbank.

b) Define phase order and explain its significance. A three phase balanced star corurected

load with (6+j8) ohm per phase is supplied by 400V, 50 W three phase source. Find
load.the line and phase currents and the total power dissipated in the
[2+6]

' 2s .TRIBtiuvAN UNIVERSITY

INSTITUTE OF ENGINEERING

Examination Control Division

2073 Shrawan

candidates are required to give their answers in their own words as far as practicable' i6l
i4l
Attempt All questions.
Thefgurrs in the margin indicate Full ll{arhs

Assuwe suitqble data ifnecessary'

1. a)Acoilhasaresistanceofl00ohms,wherrtheternperatureis20"Candll0ohms
whenthetempelatureis45'C.Findtemperaturerisewtrenitsresistanceisl24ohrns'

and surroundilg ternperafLrre is 15o C'

b)FindtheequivalentresistancebetweenAandBforthenetworkshowninfigure

below.
24{7

c) Find current frorn the source in the following circuit cliagram' t6l

2. a) Find the cuffent in 5-ohm resistor in the network shown below by using superposition l8l

theorem.
0.5

i5v i8l

b) Find the branch cunents in the circuit of figure below by using nodal analysis'

-

3. a) Find the value of Resistance 'R' such that the load resistance 'R1' which is equal to tbl

4 Q, w'ill deliver maximurn power. Also find that maximum power.

=4Q

b) Derir r- al equaiiol-l tbr inriuctance L in terms of flux iinkages and current change. i4l

c) Caicuiate the (ii average value and (ii) Rivls value of voliage wave shown in figure 14)

belo*:

4. a) Detetnine the value of current i1, 12 and I and overall fastor ol'the circuit shown in t8l

figire below for series and parailel circuit. Also draw the phasor ciiagrarn and find the

total power consumed by tlie circuit.

Ir 4o z2 b.oz u

a6 0.01H

Iz 2Q 200 pF

th-v, -50 ilz t8l

b) A coii is connectod in series u,itir a non-inciuctive resistance of 30Q across ?.40V, t8l
50H2, 1-$ supply. T'ite reading of voltmeters across the coii is 180 V and across the I8l
resistancc is 130 V. Calculate.

i) Inductance ofcoil
ii) ResisLuce olcoil

iii) Ircrver absorberl hl,ccil
iv) Porver at:sorbed b;r whole circuit

5. a) Define power l-acror and erplain w-hy in generai it should be kept on high as possiblc

in power supply' system.

b) Three simiiar coils each af resista.nce 7Q and inductarce of 0.03 FI are connected iri
Deita to a 400 V. 3 phasc. 50 I-{z -qupply. Calculate the line current and the total power

consumed.

***

TRII-1HIJV.I'I.J iiliiV rit SITi' Exam, tli'tii'',:rf l'j;ji;i,;: * ReEiit*r :r,; {::r'. i:. :,.i: .' :.
INSTIT'UTE O F ENGIhIEERN\]. G Level
BE i Full Marks I 80
Examrination Comtrol Division Programrne
BEI-, BE,X, BAME, Pass Marks 5/.
2073 Chaitra Ymr/Part I}CT. BIE.I]
Time 3 hrs.
I/I

Subject: - Basic Electrical Engineering (EE40I)

Candidates are required to give their answers in their ou.n words as far as practicable.
Attempt AUqwestions.
Thefigures in the margin indicate Full.Marks.
Assume suitqble data if necessary.

tt. a) Describe the open circuit, close circuit and short circuit with diagrarn [41

b) Two conductorqfftrc of copper and the r:ther of iron are conflected in paral1el and at t6j

20'C can'y equafiin^ents. What proportion of current will pass through each, if the t6j
temperature is raised to tr00 "C? Assume temperature coefficient of resistance at t6j

20'C for coppel as'0.0042 per oC and for iron as 0"006 per'C.

c) A direct curuent fircuit comprises two resistors A of value 25CJ and B of unknown

value, connected in parallel together vsith a third resistor C ofvatue 5Q connected in
series with the parallel group. The potential difference across C is found to 90\r. If the
total power in the circuit is 4320 watt. Calculate (i) the value of resistor B, (ii) the

voltage applied to the ends of the whole circuit, (iii) the current in each resistor.

2. a) t-tsing mesh analysis, calculate the voltage across the 20 O resistcr shown in the figure

below.

bi Lise tire noriai voltage methr*.d to find the current florving thror-rgh 10Q resistor for the [6]

neirvork sho*:t beiou'.
r0v

c) Sta.te and erplain thevenin's theorerr rvith slritable exampie. [4]
[5]
3. a) \\&at is the vaiue cf R suctr that rnaximum power is transfen'ed io it? Fit-r{'l the value

r:f this nraxirnun: po\yer fbr th.e eircuit shctq,n below"

b) $tate reciprocity theorem. VeriS' the reciprocity theorem for the network sircwn in t6l
figure below in branch cd.

?Q ?o

,i t' -ln )a) 1n

c) Define capacitance anci derive relation firr connection olcapacitors in series. t4]
4. a) Calculate the form factor and peak factor of the foilowing triangular wavefomr. [4]

100 v

0

b) A choke coil navilg a resistance of 10Q and inductance of 0.05H i^r cr:mccteci in
series rvitli a conCenser of i00 ;rF. The rvhole circuit has -been connected to 20tlY,
5A Hz suppi-v. Caicuiate (i) iinpedance (ii) c';rrent (iii)
power factor 1ir,) pcvier inpui
(-;) Apparent and reactive power oflcircuit.
16l
c) A 1il cirn resistcr, a 31.8 mH inductor and 3 i 8pF capacitor are connec,t€d in parallel
and supplied .flom a 200v, 50Hz supply source. calculate the supplv current and id]

power factor a:rd also caiculate current in each branch. t,4]

factor:?5" a) iJefine power factor and explain the disadvantages and causes cf low po\r,€r

b) A baianced star-connected icad of (8+ jO)slpm phase is connected to a balanced I6.i

3 phase 4C0V, 50Hz suppiy. Finri the iine c:u$ent, phase current and fotal prx.ver [6]

consurneC. Ta-ke RYB phase sequeiice.

c) With the help cf comection and pliascr diagrarrrs, shor-v that the power of a balanced

tlree phase load can be Cetennined using t\A,'o-watlmerers.

*,ki(

25 Tltl]:liluvAl'r iiliivLiR-!l'1'-\' Levet sr r soiii-r--*r-*-.-r.-,-:-"--*---:-:i:'=:--':**-""""'*-:"-"i"r"u':-t't-l-iu*-a--r-t-"'--'i-"'-""-'-"'''i i
lli Sf i'f {,rTI1 O ir }jN GlNi:LItIl\iC :zprogram*. p,u, ivrar*sI i
i
F-xarnim ation Csn fr*:l llivision Birl'-1i};,"ttiii.----.--',----.-----.-.i.-.-.-.-:-.---...H.-.........-......j.-........-...,---_------...-...._.."___,....i
i-Y$r1..rT!._.-i/1 _ .fi*e :J.lir, i
2072 K:rrtik

$u-,bi*SL:9ulig_flg_.ttica!pngineering(EE40t)

'/ Candidates are required to give their answers in their own words as far as practicable.
{ Anempt,4It questions.
,/ Thefigures in the margin indicate F,{tt Mqrks.
{ Assume suitable data if necessary.

i. a) Explain ideal cun'ent and voltage sources.- t4l

b) Define terrperature coefiicient o{'resistarrce. The resistance of a oerlain length of wire lS]

is 4.6f) at ZA.C and 5.880 at 80oC" Deterrnine (a) The temperature coefficient of 141

60"C.resistance of the u,ire at 0' (b) The resistance of the wire at tB]
c) State and explain Superposition thecrem with an appropriate example.
2. a) Find out the curent through 5 ohm resistor connected across the tenninal c and d in

the network shown below using the Veriin's theorem.

b) Use Nodal Analysis Method to determine the Yu, V6 and V. and caiculate current t8l
through 2.5 fj.

3. a) Find the resistance betu'een the terninals A and B in the circuit scsmeni beiow. [4]

R1 4.00
R2

b) TTree capacitors A, B and C have capacitances 10, 50 and 25 pF respectively. t5]

Calculate: lol
I6l
i) Charge on each when corurected in parallel to a 250 V suppl,v t5l
ii) Total capacitance and

iii) p.d. across each when connected in series

:c) State Maximum Power Transfer Theorem and also prove "maximurn power will be

dissipated v/hen Ri6"*6 RL"

4' a) Derive the expression for electricai current in a pure inductive circuit when input

pov/er is VrSinwt. Draw the wave forrn of voltage and current and phasor diagram of
the eircuit. Show analytically and graphically that it does not consurne real power.

b) In the given e.ircuit, {ind the current through the inductor, w-hat is the equivalent

impedance?

c) Find the peak f'actor ancl form fact+r of the triangular wave shown in figure beiow. t4l

5' a) Erplain the impofianr:e tl pcrver factcr in ;ur ac circuit, with suitabie example. How
power factor can bc improi,eC'i
14)
b) A ti"*'ee phase star ccnnecied systeni rvith iine voltage 400 V is connecteci tc three
iB]
io:rt'is:2.5'10o, 111.-2.a" and ii110" {also eonnectcd in.qtar). Finc! the iine to line i4]

system.curT ent, t*tai pov,,er and current in the neutral of the

systein.c) Define pl1as* sequence and rxpiain irs significa-npe in tlrree pirase

1< TRIBI{UVAN UN] VL- RSTIY Exam, BE Full Marks 80
Leve!
INS TITLTE f.)}- F;}i G N EE.RI]A{ G I]EL, BEX. BCT, Pass Mari<-s -12
Prrgramme BAI\48, tsiE,
Examination Control Division 8..,\Eri. Time 3 hrs.
Year / I':rr1
2fi72 Chaitra llt

Syliect, - Bas.ic Electlical Eng_rneering iEE4At)

r' Candidates are required to give their ansrners in their own r,vords as fat as practicabie.
{ Attewpt All questions,
/ Thefigures in the margin indicate Full.Marb;
{ Assume suitable datci if necess*ry.

1. a) A 60 W,24A V incandesceni fiiament larnp is switched on at 20oC. The cperating

temperature of ihe filament is 2000'C. Determine the current taken by the lamp at the

- instant of switching ON. the temperature coefficient of resistance of the f,rlamenl

material is 0.0045/K 16l

b) A battery of unknown emf is connected across resistances, as shown in figure beiow. t5l
The voltage drops across the I Q resistor is 20 V. What wili be the current reading in

the ammeter? What is the emf of the battery?

8n llo

c) What do you mean by ideal and practical "";:*. and current sources? i5j
2. a) Find the power dissipation in 15 fj resistor shown in figwe beiow using mesh

analysis.

theorsm.b) Find current on load resistclr Rr-, if its resistence is 2 CI, using superposition t6]

?ft

2rr ?fi

c) State and explain Norton's lirecrem with an appropriate example. I4l

3. a) Find the value of R1- 1-cr u.hich rhe maximum power is tr"ansferred iri the load
resistance Ft1. Aiso tlnd the rnaximi:m polycr lhat can be translerred krad
1o the
resistance R1.

i8l

+ at i ii
a rr. _,;

I 20 Rg

I

b) Derive the expression for the inductance of incluctor in terms ovaf *itus p,,h,/y*svicaarr
dimensions.

beiow.c) Caiculate the average and rrns value of fuIl-war/e rectified sine wave as shown t4]

t4l

4. a) pcsAcacionnpwcgnaielreeccrcituptfaeaihntCcactcsoeioenrnosaspufniaspd1trpian0(llyigi{ie,i)plocpwFafol'iactwIhurfeelaartsthiecsceotia1rnpcnis;aucuTerimtahceoleloedfcn.i3uscA0riosrretomsinnobtgidininnroaasfteweiaoaricunerhesnissU"wiusricttutaohfnnntc*ante*neitocroilntrife;ddd2Tui0hactoegtfiJrxataromicntea2. 4lso0ecfruiVTerrs5,enw5mtsiHtahHnidzsa tBl
b) rpHFl.-hvo,$haraosaosicerusacepdpriipraiaeclegysuir.taipotcm,arata.ihl8cc0wtuipvliateFhtepiasobrwkereaseipnrstctaahi:nnrdccpeuraercrraaefcln8lteitvsol.e,,Ttpochoateapwnlaetcchriutecororrcenoonsmftublnf2ri:n0oeapdmtFibosnyauntiphdspeafleyncd,iirnpcbdouy,wict2.tea4Arn0lcfvsae,oc5otso0fhrI-0oIo.zw1,f
l8l
-5. a) Develop relation between phase voltage and line voltage in 3-{ star connecte6 systein. i4l
b) I8l
For the circuit shown in figure below, calculate the curuent tkough the neutral and the
total power consumed in the loari.

4'i5 V
baiarrced
supp:y

\,) Erplaitr with connection iiiagrarn ihe measureme[t of 3-$ power rislng two

1 ,?timetfis.

***. t4l

T'RIBHLiV Al.i t.rl{IVtTRSiTY Exam. New:Back (2066,& Later Batch)
i Level i BE ; FuIt Marks : 80 i
INSTITLITE OF ENGINEERING
Examixration Control Division

i32071 Shawan
ilfn-"Tlr*{:."t*sIl:,i]H{k-,_l?.'* lt"'u: irnlit::rsy':-I--rl.lrr, j

i

Swbject: - Basic Electrical Engineering (8840 1)

Candidates are required to give their answers ln their own words as far as practicable.

/'t Auempt any h-iygquestions.
{ Atl questions carry equal marks.
{ Assume suitable data dnecessary.

a) What is the diff'erence between thc potential difference and electromotive force? t4l
b) Find Ir, Iz and 13 in the circuit shorvn in the figure using Kirchh-off s iaw. t6l

12v

1 r-\

c) \tr4rat is the value of the u-nknorvn re-qistor 'R' in figure belorr,. if ihe voitage drop I6l

across 500f) resistor is 2.5 voits?

R 500fi

2. a") Use the node voltage me.tiiod {'nodal) to find 'rtrre current {lowing thror.rgh l0f) r*sist<-rr I8l

in the rietrvoik shor.vn figure below.

10Q 2A

L v.50

b) For the circuit shown in figure below, calculate the current in the 10 ohm resistance
using Thevenin's theorem.

ioj

5fl
i0rJ

" il:f#;tr.Jfi3' dissipared in 3f,) resitor in the circuit shown in figure berow using i8t

1C)

t0v

b) An inductor is to bccmmeorHmew,aiisctdhae1r5ccw0ruo0iiats.htse-cstoehpcetpioennruawmi iarbree",awooorfut5nu0drrnoqJn;.":aqc"iirric"fauthlaegrirviereoqnnuktcheoadrtevraehllauavetiivnoegf

mean length of 40
inductance is 500
permeabiiity of the

4. a) ti0Ahm'e7p42pr1oop5vwoevwe,rtehrf3eafcpaothcvoaterosrrteao,llai05gp.ag9oiHnl*agZigt.giAfinandcgbut.oacr,t.kiocnoaflmccuaoipatoaterctiattokhre"cs"i.,5"0p.o*K*iW;r;."L]pdoowinerdpfeirrolutamr*aiscnuroposprsdryethrmetoaliinrnaesistaeot i8l

b) Three loads (3 Fr+inj5d.9t.h] eo,ph(3as0e-i4cu0n)oenatsn,dri(nge0c+uj6rr0e)netsaarendcotontnaer cpreodweinr derta to a 3 phase, 18t
a) supply. absabed.
200 v t8i

5. Define cycle, Time period, anguiar verocity, frequency,
alternating quality"
everage and rms value of an

b) A series circuit consists o(3f0r0ets+isgkn0c')ev.ecqauraclutloate4Qtheafnotllroinwdiuncgt:ance of 0.0i I5l
[10]
i)applied voltage is 283 sin FL The

Power factor
ii) Expression for i(t)
iii) The power dissiputed in the circuit
iv) Voltage drop across each
Draw a phasor diagram elements
v)

a+*

'iRIIl ill.r V;\i'J Ui{Mlll ij lT V Exarn. leguldr'.i: ' " ""i, t
Level
IIN STITUTE OF ENGINEER}N $ Rtr Full Marl,r-q 80
Exarninatinn Control Divisicn Frograrnme
Year / Part BEI-, BEX, BCT Pass Marks 32
?i]Tl Ctraitra
BIE. B.Asri.

Ut Time 3 hrs.

S-y"Qies!::ee{g--slg-.gig4l-"eswr:r:,s(!!!-9!)--
r' Candidates are required to give their answers in their own words as far as practicable.
{ Auempt All questions.
,/y' The figures in the marlin indicate Full-Marks,

Assume suitable data if necessary.

1. a) Discuss voltage and current sources in brief. Also justifu the statement "Terminal voltage
goes on decreasing on increasing load current."
16l

b) The field winding of d.c. motor connected across 230 V supply takes 1.15 A at room

temperature of 20"C. After working for some hours the current falls to 0.26 A, the supply

voltage remaining constant. Calculate the final working temperature of field winding.
11254-5.Resistance temperature coeflicient of copper at2A"C is
16l

c) Discuss roles of Kirchoffs laws in electrical circuit analysis with justification. t4l

2. a) Determine the value of load resistance R; to receive maximum power from the source.

Also find the maximum power delivered to the load in the circuit shown in figure below: t8l

t--

I
I
I

I

I

r-\_1.

100V*

I

i
,l

I
I

Dl Use the superposition theorem to determine the current in the branch 'AB'of the net*,ork

shown helor.v: I8l

"'3' fff?*:i3).anairsis to calculate power dissipared by 5a resisror in the circuit shown in

t8l

b) Calculate the curent flowing through i ohm

current method. resistor for network shown below using loop

4A l8l

---_---i1

-!

---!:- 6 V

;;_ilr'',r,,tfo*i..i;_,:ffi:[*L':i,tT4. a)
Derive the equation for instantaneous curreonwt flaonuaD]lnyrgtIicwtahlilrryo,"ualgn.ht*i]ga"rrap"pu,hmreicacolalyrpva,orcrrirtrtoarg?erw:ha,ien#dn

ff :,H? ,lJ,
not consume ,.ul

rmb) ,Tj

*) the equivarenr capacirance of 4 sroup of capacirors when thev
3:ffi;r"J',fr'Ji:;r:"r

i;;l0'rii. rir-;;#;i;ls.lH;J,::;5'a)
b) rVAm,sse5vr0aielHusezRss-oLuf-prc'pocirlir,racgFueinitad.hcrtaohsvesin"*g"uuR""n"=n*lr*I^r0n,i0rone*t*s,g.LuA:"0Itsi.orrr2*dId-ior;ai"&ni";drr0;";ud="iari2gugr..2a7pmopw.Fe-isr-,,ferpdvowfrr.eovrmfraacctro0r0, 14l
Each lpinheasevoaoiftnaajs3te-h1.eihsats4oe4t,a0dr eprotaw-ceoi.n"nwecrte,,d,crwooai*drri1cmo,n.s;isht-s; 16l

The of an impeda nce z:20 L6o. ohm.

consumed by each nhase
watrmeters
of the rwo

c) Derive the expression for inductance of a coir in terms of its dimensions. 16l

*d<* t4l

25 ]'RIBI{UVANtINIVI'lilillY I,lr u nr. BIJ Iiull N{arks 80
INSTITUTE OF I]NGINI'I iIT IN( ;
t,t'r'cl rii,r,, si,r. sc'i'. Pass Nlarlis 32
Examination Control Division
I'l'og rit nt Itt c lllE. t). Agr i. l'imc 3 hrs.
2070 Ashad Yt':rt'/ l'ru'l
I/I

',// (lancliclatcs are rccl"rircdto givc thcil rrnslr,crs irr tlrcir olvu rvolrls as lirr as practicable.
,1 ltantltl All cltreslions.
,/ I'ltt'/igures in lhe margin indiculc Iiull MurAs.

'/ .1,s,srtnre suilable dota i/ ncces.\'ury).

l. ir) What is the factor responsiblc lirr thc devialion of'thc practical solrrccs frorn their t6l
t4l
idcal behavior? Explain the eflect o{'this lactor on 1hc tcrminal charactcristics of the
I6 I
voltagc source.
I4l
h) Writc dorvn the steps to calculate Nortor-r's ccluivalent rcsistance in the circr-rit u,ith a t6l

sLritable example.

c) A concluctor materiai has a fiee electron density of 102a electrons p.r n",3. Whcn zr

voltagc is applied a constant drifi velocity of 1.5x10-2 m/s is attained by the elcctrotrs.

ll' thc cross sectional area of the rnaterial is I cm2, calculate tirc magnitucle of thc
ctrrrcnt.

ir) Lrplain u,ith neat diagram and rvrite the equations for Dclta- Star Conversion and Ior

Star-l)elta Conversion
Re.s.l,) l:inrl thc equivalent resistance across the termir-rals A and B,

6 Ohm

3 Ohm A 2ohm 3ohm

4 ohm 4 Ohm 5 ohm 10 ohm
6 Ohm 6 Ohm 2 Ohm

a 6 ohm

c) "'l'hcvcnin's theorem and Norton's theorem are dual of each other". .iustify the t6l
t8l
3. a) state ment u,ith suitable example.

[Jsc Superposition theorem to l-rnd the current 11 through 2 f) resistors in figure

below.

10O tov r

5A 2A

20Y

25 TFJBHUVAN{JNIVERSITY Exam. ;,=1 j :':.;;=ri"r.iTi.:. ;iRiEular],'..i -;{;;:"f ,;;1:ji
IN-STITUTE OF ENGINEERING Level
BE Full Marks 80
Exrarnination Control Division Programrne
IJI]J-,BEX.BCT,BIE, Pass Marks 32
]l.Asri.

2070 Chaitra Year / Part \tt l\ L Time 3 hrs.

S ubi ect ; - Basic Eiectrical Engi1ee518- ;(EE+ {) !

a;did;itt ;i; Edi.ei itgive their answers in their ontt viords as far as practicalrle.

Atternpt A!! que stirtns.

The,figures in the margin indicote Full Marks.

Assttmc suitab!e data if necessary.

1. a) W6at do you unCerstatd by terms 'resislance' and 'resistivity'? On u'hat tactors the [4]

resistance offered by a conductor depends? t6l
t6l
b) Two resisiors made of different materials having temperature coefficienis of
resistance clr = 0.004i"C and crz : 0.005/C" are connected in para1le1 and consume
equal pcwer at 15'C. What is the rate of power consumed in resistance Rz to that in

R1 at 70 c"?

c) Caiculate the value of unknovn resistance R in the circuit shou'n beloq' and the

current flowing tfuough it u,hen the current in the branch oc is zero.

4fi

10v tsl

2. a) Calculate the output voitage, Vo for the circuit shown in figure below using Kirchoff s

laws.

2sl

2A

tti--vv\-l
i,-lI !.: D,o Vo

Duo )z

b) Determine the power dissiPated bY 5Q resistor in the circuit shoun in figure below by t6l
applying nodal voltage analYsis.

c) state and explain zuperposition Theorem with an appropriate example. lsl

3. a) Por the circuit shou,n in frgure below, what rvill be the value cf R1 to get the€

maximuin pow'er? i&hat is tie rnaxinium por,,.er delivereri to the ioad? t8l

1- i4l

b) Determine the current in 20f) resistor of the network shown in figure below using Star
Delta Transformation

c) State the definition of the capacitance and from it write an equation for the charge t4l
t4]
stored in a capacitor. t4l

4. a) :Derive the equation for instantaneous current flowing through a pure capacitor when t8]
t4]
excited by AC sinusoidal voltage V V* Sinot. Draw the waveform of voltage and t8l
current and phasor diagram ofthe circuit. Show analytically and graphically that it
t4l
does not consume real power.

b) A coil takes 1.3 kVA nd 1.2 kVAR when connected to a 240 Y, 50 Hz sinusoidal

coil.supply. Calculate: (i) Po*'er dissipated (ii) Current and (c) lnductance of the

c) A Circuit consisting of a resistance of 30Q in series with an inductance of 75mH is

connected in paratlel with a circuit consisting of a resistance of 20Q in series with a

capacitance of 100pF, if the parallel combination is connecte.d to a24AY,5AHz,

single-phase supply. Calculate (0 The total current (ii) Power factor (iii) Active and

diagram.reastive power. Also draw a neat phasor

5. a) What are the two ways of connecting a 3-phase system? Draw their phasor diagrams

and write down the relationship between phase and line voltages and phase and line

aurrent for these system.

b) A220 V, 3-phase voltage is applied to a balanced delta connected 3-phase load of

phase impedance (15+j20)4. Calculate:

i) The phase voltages

ii) The phasor current in each line

iii) The power consumed per phase

iv) Draw the phasor diagram

v) What is the phasor sum of three line currents? Why does it have ttris value?

c) Explain 2-wattmeter method for the measurement of power in a balaoced three phase

load.

r**{.

25 TRIBI{UVAN UNIVERSITY Exam. - .Nerv Back(2066 & Later Batch)
I-evel
' - INSTITUTE OF ENGiNEERING BE FulI Marks QN
Frograxnme
Examination Control Division. BEL, BEX,
Year / Part
2S69 Ashad T}CT, BIE, Pass Llarks )/.
B.aeri.

M Time 3 hrs.

- Basic Electrical (Efr 40J)

Candidates are required tc give their answers in their own words as far as practicable.
Attempt any {ive {luestions.

The figures in tlze margin indicate Full Marks.

Assume suitable data if necessary.

l. a) Define the temperature coefficient of rcsistance and explain the effect of temperature t6l

on resistance ofa substance- 14l

b) A lead wire and al iron wire are connected in parallel. Their specific resistances are in tol

the ratio 49:24. The former carries 807o more current than the lauer and the latter is
4TYolanger than the former. Detentrine the ratio of their cross-sectional areas.

c) Using series-parallel combination of resistances find the current delivered by the

source in the following circuit.

2. a) A lkm length of wire having a diameter of 1l.7mm and a resistance 0.03ifj is drawn LJ.:,ttl

so that its diameter becomes 5mm. what does its resistance become? i6j

b) Use Kirchhoffls laws to detemrine the magnitude of source cun.ent and polarity of the
source S, if the current flowing through branch BD is 0.2A from D to B in the circuit
_*__-v_
shown below.

c) state superposition theorem" Find the current in 0.5e resistor in the follcwing

[6]

3. e) Derive an expression for the equivalent inductance of two inCuctors when they are q

connectec in parallel (i) Aiding coml:ination {ii) opposing combinatica t8l
[8]
b) Applying Thevenin's thtorem, calculate the magnitude arrd <lirection of current in the
135f resistcr in the circuit shown in the following figure.

180Y

200v

50v

4. a) What is power factor in ac circuit? Explain the disadvantages of low power factor. i4l
b) When a voitage v- 10sin(50ft-60")v is applied to a series ac circuit, the current is
I;
i=6sin(5001-10'). Find (i) Power factor (ii) Circuit parameters (iii) Apparent, active
and reactive power (iv) Also indicate wkther the circuit is capacitive or inductive and t6l

why? t8l

c) Derive the expressions between phase and line voltages and phase and line eurrents

for a baianced star and delta connected lmds.

a) Following figwe shows a series parallel circuit. Find: (i) Total impedance (ii) Current

drar*a from the circuit (iii) Voltage across the parallel branches (iv) Cryrent flowing
through each parallel branch (v) Power factor (vi) Active, reactive and appareri

power. Draw phasor diagram showing V, 11, 12 and 13.

*-z;*I 4CI- 2{l r

b) what do you mean by complex power? Explain it with the help of an R-L series i"4j
14]
circuit and power triangle.
i8l
c) An adustable resistor R in series rvith a capacitance of 25pF draws a cl]I"rent cf 0.8A, l8l

when connected across 50Hz supply. Calculate:

i) The value of resistor so that the voitage across the capacitor is 'half of the supply
r-oltage.

ii) Power consumed a:id

iii) The power factor

5. a) Three impedances of,(6rjs)o, (s+j6)o, (3+j4)9, are connecred in star to a 3-phase,

4 wire system for which the line voltage is 400Y. Find the line currents, and ictive,
reactive and apparent power per phase. Abo find the current through neutral wire.

b) Prove that surn of, the readings of tvro Wattcmeters is equal to the total three phase
power in measurement of power of 3-phase circuit by two wattmeter method.

*H

)

25 II{ll}ilti\r,\\ U\il\/il{srr Y Exam. Regular

INSI I'fi-l I'E Oi" ENGIN}rlrli IN('i Level RE r F'ull Marks 80

t l*:nx,j em,-

;;;;;;;-""ti BIE. B.Agr:i.

t:
Examination Controt Division ri ' Pass Marks )1-

i 2tXr9('haitra '\car/l)arl l/l

-l'inre 3 hrs.

S uhjcct - llasic I : lcctrical t:nginccr.i ng rt: t: t0 I t

canciidates are required to gi'e ,rr.r. unrr""; ;; ,;";;:o,, *ora. as lar as pracrrcabre.

Attentpl any liive questions.
l-he.figures in the ntargin indicate Full Marks.

A.s's um e,Eu i t ab I e da ta iJ' ne c e s s a ry).

l. a) Explain the methods for converting practical current source in to practical voltage t4l

source. t4l

b) Calculate the power rvhich would bc dissipated in a 75 f) resistor connected across

XY in the netu,ork shou,n belorv.

20o

200v

75fJ.

20e) i8l

Y

c) lriircl thc currcnts I1. 12, 13 using Kirchhoffs Law and also find the power output of

cach voltagc source of figure belorv?

<I-*. ___* -r
T

2. a) The resistivity of a metal allof is 50xi0-8(-)-m. A sheet of material 15 cm long.6 cm t6l
t6l
wide and 0.014 cm thick. Calcuiate the resistance inthe direction: (a) along the length
and (b) along the thickness.

b) Use Norton's theorem to calculate the value of R that will absorb maximum power

from the circuit shou,n in the figure below. Also calculate the maximum power drau,n
by it.

::,#

c) I, the netrvork shou,r-r below. llncl tlie r,alue o1'resistance lL and the currenl throuplt it t4l

u,hen thc current thror-rgh branch I)A is z-eltr.

j. ir) liipd the current through the 10 f) resistor using loop-current rnethod? t8l

4n en SIt

l0v

Fig:3.1 t8l

b) F'ind the current I in the circuit of figure below by applying nodal voltage method'

---)'l t2Y

18V 6f)

4. a) Explain generation of sinusoidal emf with diagram and define angular velocity. t6l

b) A sinusoidal voltage is applied to three parallel branches yielding branch currents, t6l
Cos(rot-60') and
irl4.l4 Sin(rot-45'), i2:28.3 ir7.07 Sin(rot+60o) (i) Find the L4l

complete time expression for the source current (ii) Draw the phasor diagram in terms

of effective values. Use the voltage as reference.

c) Define inductance and derive relation for connection of inductors connected in

parallel connection.

:i TUBTILVAN U),i\-EaSiTY Jiii--EL:ugrl::9-1_--.._l,iBnrrEoEprF!rc-"96;6r_uBi_itrrr;sk}.r-"T*sjto*'_)'
NST ITUi'E OF E\GI^\IEER.T\,-G . uL.L! JLj\!
, l'ass Uarks j J:
Erlmi nation Conrol Division Frogrlrnme : BCT, BIE,
' R r,*i ,
2068 Shrau au
if.sri.i r l.t_ _i!_..!:_t____- :_:ilira---_=}r._l

.-_-*_- Swbject. -pasic Elecfical:ng
*__*l
_

Ca::,.1iCates are required to give their ans*.ers in tireir own t'ords as iar as practicabie.

.l;iensi an.'., Five cuestiotts.

The jlztires in the m;;.gin indicate Full ]ta.;.ks.
.L:j::in€ s:t:t;tble Ca:;t if necessar,..

z') rt,-ia: is the iit-f;rence bet..r.een tl:e por:n:ial c1:fieren;e and electromoiir': for;e?

L, ;i-ire resistanc e an,l r:sistivil.,..

': r ll-'--..;-: ..t,---.= .r.,..r1r.J€ ol :he ui.:lr;ori-n rr'sis:or 'R.' ir rh: ci;cuit belc',r, i. ti:e voitag:

.iicp a:rcss jt-]CO ;:sistoi rs 2.5 r,oi;s.

P-.r^r5Aifu-i1-re^v\,I- ;:cr i

:-12\,' i I

) "'"+

.ll iiii
r-i-rl -

Usii:f su::rposit:on il;:orem, ria.i il.- curiiii in EC resisror ol tire n:t.-r'ork sho*:r

Og,O'rr.'. '\

I LJ]

Jo\l I t8l

I 5\l
t
i
t_

b.t Lsing N:dal .{naiysis methoc to finc the curr:nt in incividual resi:;tors of the circuit

sho,.'"'n bciorv.

1CA

\)
('n
:3A
<'-41

1

I

3. a) Find the value of R1 in the netw,ork shown belorv to obtain maximum por,,,er in i'. tsl

Also find the maximum porver in R1.

b) Derive the relationship betw'een the voltage ancl crin'ent for a purel,,.ind,..:::..-: crclrit t6l
Ll)-1)
excited by ac voltage scurce. Also shor.v that the average por".i consurnetl br a prireiy, i8l

inductive circuit is zero. t8l
t4l
c) Tr'r'o coiis of indr-rctance of 4 and 5 Henry are comected in parallel. If their mutual t4l
inductance is 3 Henrl', calculate the equivalent inductance of the cc.;rt,ination if t8l

mutual indrrcirnce:

i) Supports the self inciuctance, antl ii) oppose the sellinductance
4. a) The impressed r-oltage a,-'cl thc curent flo*-ing through a circuit are:

r' = -i00 sin (-100t + ;r,'3) and i = 5 srn (,100t - n/6). Determine the
i) nns and average value ofv and i,
ii)
Radian through *,hich it's \recror has gone r.vhen t:0.001 sec.
iii) Phase difference, and

iv) Pou,er consumed in the circuit.

b) A voltage of 200/j3'is applied across impedances in para1lel. The.,,al,re oi

impedances are (12 + J16)() and (10-J20)Q. Determine the kw, k\"'.\ and k\r^{R in

each branch and the po\\'er factor of the r,vhole circuit.

5. a) Define power lactor and explain the disad'antages of lo*. p f. u'ith eranrles.

b) Compare the star and delta 3 phase con_nection.

c) For the circuit show'n belorv, calculate the current tl.,rough the neutral and. total power
of the circuit.

380V
balanced source

6. a) A star connected altemator supplies a delta connected load. The impedance of the t8l
t8l
load branch is (8 + J6)e. The line voltage is 230 volt. Determine:

i) Current in the load branch ii) Power consumed by load

iii) Power factor of the load iv) Reactive power of the load

b) Describe the measurement of power in a unbalanced three phase Ioad by trvo

***

lc TRIBHUV;\N I-INIVERSiTY hlxarn. BPi ,eiiifl*S,t,..,;. Iir,,, lli..;,,i:, 1'1,;
NSTITUTE OF ENGINEERIh] G Level
Full Marks 8ij
Exarnination Control Division Prograrnme
BEL,BEX, i
2{168 {-haitr.r B.BCT, BIE,
i Pass Marks i 32

Ut 'l-ime 3 hrs,

'/ Candidates are required to give their answers in their own words as far as practicable.

'/ Attempt any Fiygquestions.
,'// The figures in the margin indicste Futl Markq.
Assume suitable data if necessary.

1. a) Explain emf, potential difference and current with a circuit diagram, .i' -

b) The temperature rise of the machine field winding was determined by the

measurement of the winding resistance at 20"C the field winding resistance was
160 Ohm(CI). After running the machine for some hours at full load the resistance is

185 C). If the temperature coefficient of resistance of the copper winding is

4.3 x l04l C at 0"C. Determine the temperature rise of the machine.

c) Find the equivaient resistance in the figure shown, and power dissipated in the 5CJ

resistor.

2. a', -alcular__ re value of R that wmiallxia.rbnsuomrbpmow\rEr.f 'llilm pr_,r from the circuit (sho*n in
-ftre figure). Also calculate the
drawn by it.

48V

b) State Norton's description theorem and list the steps for Nortonizing a circuit.

Compare the Norton's equivalent circuit to the Thevenin's equivalent circuit.

c) what is the total cost of using the following at Rs 7 per killowatt hour?

i) A 1200 W toaster for 30 min
ii) Six 50 W bulbs for 4 hours

a iii) A 400 W nashing machine for 45 min.

3. a) Use Nodai analysis method to calculate the current tfuough ttre 15fj resistor in the Loj

figure shor+n below.

8(} 10()

b) Find the current I as shown in figure below using star - deita transformaticn. 14l

c) An air cored coil is 2.5cm long and has an average cross-sectional area of 2cm2. IV
Determine the number of turns if the coil has an inductance of 100 pH.
[61
4. a) Calculate the average value, rms value, form factor and peak factor of the saw tooth

wave as shown in figure below.

50v

b) What do you rnean by reactive power in AC circuit? Explain it by ccnstructing phasor i5]
t5]
diagram for real power, reactive power and apparent power. tg]

c) Describe and illustrate the phasor relatiorship that exist between the voltage that tS].
appears across the tenninais of a pure capacitor and the current that flows through it

in steady state when the capacitor is excited by a sinusoidal source.
5. a) A voltage *f Zaallo v is applied across impedances in parallel. The value of

impedances are (12 + j16)a and (10-j20)e. Derermine rhe Kw, KvA and KVAR in

each branch and the power factor of the whole circuit.

b) A delta connected load of Zan = 52245"{2, ZBC = 522-3A"e and ke = I0l0o(-l are

connected to a 380V,3 phase ac source. Find the magnitude of the line currents and

ABC.total power.absored by loads, when phase sequence is

b) t41
c)
t6l
\".
;tp

*?
{*?

s
-.#k-?

arr.#

+

i... r. ,_.. : j,- ,LA I RlllHUtrrAN- Utllvlll SlTf i- Exam. _.'_ Nery :lBacFllu(l2F0IV5,l:hBrkai*r'Li hi

TN:STIJ UTE oI E',GL\I:.IIRL;6. .EE:"' r 80,-.,. -.' ,

-Exainin:ition Controi Dir,is ion BJL, BEX, .
Pio$ramme BCT,,BIS, r*iMuir" l:z
B'Afl"i.
2067 Ashwin ,,Yter/&lt I I{_l Tiqe . 3hrs.

-_.'.---__'+

t./ A9t:tle1ml*p:t::aanrye.Frievqeuqiureedstitoongi ive rheir rnsrvers in their own words as far as practicabte.

/ Assume suitab/,e clata if nec"srory.*----

:

1. a) What are ideal voltage and current sources? l4l
b)
You are'uglng a heater 2ZOV/IKW macie material o^f :conductivity:'16666_6i ,

mho/cm. The wire has- t-h_:i_c-k_n-^e-'ss of 0.5mm. _oj_a

gtven wrre used in buiiding heating elernent? t6l

c) Find. the equivalent resistance in between point AandB in figure below. The

corresponding resistance values are indicatedtin figure. All the resistances are in

t6l

I . rl .

-1 :'

a) Using nodal analysis find the current through the 5 ohm and 3 obm resistors of,,the
following circuit.
' t: ' ..

t8l

,.),

..

o) Find the f?wer dissipated in 10 ohm resistor using Thevnin rheorem of the following tg]

vu. a.rL_ '

J- . a) Ernd the power.dissipated bir 5 oi:m:-esistor oI rhe following ,.': using Norton's
':'theorqm.
' circuir

b) .Detenline equivalent inductance of induclances Ll and L2. when they are connected t8l

.in parallel ttoat t

4. a) What is the average power consumed by a circuit containing an inductaace only, lraL"tl

.when]suppIiedbyanaCsource? Lol

b) At 127 Hz frequency, an emf source ol 6V sends a current oi i00mA through an

inductive coil. If the frequency changes to 456H2, the current drawn by the c]rcuit

becomes 50mA. calculate the inductance and resistance of coil.

' c) D-etermine total power consumed by the following circuit. Also draw the phasor

diagram.

265.15 rrr

10'o

200v, 31.8 mH
50 Hz
,
:

5. a) 41rL inductive load of 6 kW at power factor of 0.6 is connected across aZZOi,5OHz I

supply. Calculate the value of capacitance to be conne.r-c.-ted in paraliel with the load to
. . :bring trr-e resultant power factor of 0,95 lagging.
. l4l

b) Justifiz the use of two wattmeter to calculate the power of 3 $ road. [4]

c) For the deila connected load as below, determine (i) phase currents (ii) total power l
consumed (iii) line currenrs.
i8l

b T'- r' . ,[axa]

6. Describe briefly: I :!li -.::.'_
. . :' l.-::i.,!'
-,. : a) ,Maximum power transfer theorem.

b) Disadvantage of low power factor
c) Reciprocity Tireorenr
d) Current-and supply frequency relationshrp oi a R-LC seies circuit

+*'k