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Electro Magnetics Question sets for engineering students.
Typology: Exams
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TRIBIILIV ;'rlJ I iNiVERSITY
Examination Control Ilivisiori
2$?8 Bhadra
Candidates are required to give^ their answers in their^ orra^ ltords^ as^ frrr^ as^ practicable.
ltte ntpt^ A^ I^ I^ q^ it( itions.
'{he figures
in ihe margin indicate
Necessary dfitij a_re a{tached hgls-t+,itk.
,d represent a vector and d*6rrr1rs denotes a unit vector^ aiong the
.lirection (^) given by the
subscript.
Assume suitablc dota dnecess*ry.
i. (^) Givenapoint P (-2, 6, 3) and vector field E= yd+ (xy+z){, express
and E in
spherical co-ordinatb system. t5]
x-axis and uniform sheet charge of 25 clmz lies ol z:0 plane.^ Fhd d at point^ (1,2,4j.^ tI
associated with the field D
Eyzdz + x"yd, (^) + zAz C
4" State ccntinuity equation. Given the vector cr.urent de;isit1,
i =
1Ap2frp-,lpsrnz$d6 mA/mz. tretermine the current f<.rllovriirg outrvard the circular
band
$<2n,2 il iregion2)
has pr,=^ 10. if there is auniicrm
rrragnetic field H (^) = 56x * 6ey + TezA/m in region 1, find d and }j in region 2. t8l
cartesian:v D=$p-{.
AxryAz
I
1+
p op poq^ sz
.. .- .: 1 f(r2D,)^ I d(D"sins)^ I^
&+
r' Ar^ rsin^0 eS^ rsin^0 d$
Gradient
carresian, vv^ = s 6,^ *^ *a. *^ *a"
dx6y'az
cvtindrical: vv=9l4, *
1 9Ia. (^) * {a-
0p
o p0{l
Az
av^ Iav. l av^
Sphericai:Vv"* (^) =?6, +:iia. +--:
6 r 6J rsrnu =i-irdO
Curl
c-artesidn:vx fr =fgrr.-
aHi
L -l.g.-fl.]a
.,.[5r.- tr ],
(0Y Az)'taz ax)'\Ax AY)"
9!.
3L'lu *(
Ht
au
"L. *^
lf
'ot'o
4"..|u
'
\ea$
0z)'(az 0P)' P\
0P Ai)'
=
=[LEtrr
e)
.
1f+=+
g'H,
+.
lf
q('9,
).
,re[--aol-- a+ J"'";L'*s
aS
n, f'
*;[
a'
n (^) )".'
Laplacian:
Cartesian:VzV= (^) ++*
i*(rffi
i#-#
= i* i" ffi
#*fd
(',ru
iii
.
i0. A 50 f) lossless iransmission line is 0.4 l" long. The line is terminated with a load
Zt:4A +^
operating frequency is 30il^ MHz,^ find^ [2+2+4)
a) reflection coeflicient (f)
b) standing u'ave ratio (s) and
c) input i:npedance^ {Z*)
ltr.Explain why TEM-wave doesn't exist in a rectangular waveguide? A rectangular
waveguide has^ dimensions^ a^
:
:
€,
: 1, lrr:
be transmitted in the TE1,6 mode" [2+4]
studied. [1+l
Divergence
AD' (^) AD-
Cartesian : V. D (^) =-3 +^
=t
*-
0x AY Oz
I
r6(pDo).1dD0,0D,
CYlindrica I :^ V'^ D =
:
-=--
T --=-
T -;-
' p (^) dp poq oz
.,-i l8(r'?D") I^ a(Dssin0)^
I 6Dr
spnecncal: r"^ u=-T-*6.-^
" r.rB- A
**irin
gE-
Grailient
av^ av^ av^
Cartesian:VV (^) =--O* -a^ *---^d,
AxaY'02'
= $
a, *
!*a,
*a,
o? poq^
lav^ I av^
*;H uu *iiln;6:",
Curl
t^'{, oH, )".
(au- (^) oH"f. ,
(au, (^) oH- l" c-artesian'vxfr=l
al' *' !a- "ir
-***o
ur!L)I4rr'"^"-l lu,^ +l^ i-r-gi"^ la,
a),
a,
j"' '[a,
f'
-l
a" f'
cyrindricar:v,r=[;
r+
E )"r.[.a,.
-?#f (^) r.'
;LTp
(^6) )n,
sphericar : v x^ fr (^) =
-r*
[
-. {'-l
gL
u(t,
'si"e[
ae
a[f'
' i\rsirie a,[ 0r
'
tl. ar &^ )
Laplaeian:
#,
#,
-#
cyiindrieah v21I =;*(-#)
*,#ii
spherieal: vzY
i*(.'11.)
ala('r#)
TRIBHUVAN TNIVERSITY
OF ENGiNEERING
Examination Controtr (^) Division
:
gl (^) gg[g-gagjl{[! fsx -i o-ii
/ candiiiates-are required to give their zurswers (^) in their or+:r (^) rvords as far es practicable. t
{. The figures in^ the^ mnrgin (^) inrlicate Full.ltf (^) arks.
,.
"
-lsstintc ,tltit,iblc ,in;o iJiiiliSl-- Unecessary. $I'','i;,*ii1. , ,
-;tffi
_)
?Hm;**l
s
1' (^) Transform the (^) vectar
into (^) spherical co-orclinates ai a point p(x = -2.
Y
: -3' z': 4')'
lsl 2' (^) An intinite
pL (^) - 2nCrm lies alcng the
pointcharges
0, 1)and(G, (^) 0, -1). (a) Find (^) il at(2,3, -41.
3" (^) Dbfine uniqueness theorem" Find (^) the energy st.red (^) in free space (^) 1br rhe region 2mm< (^) r< 3iir*r, 0<0<90", 0<0<90", given
: , =-*-'
'-'
1MrL
r! (^) r;'v
'vrwrtrroi
l'2*
a) --\r erd (^) b) alcosOy
4' (^) using the continuitv (^) equation elaboi:ie (^) tire coirceiri
Rela:taiion Tirue constant 1RTC)
derivaiions. (^) Ler ;=+- (^) ;,p
censity (^) in a given
r, Y
region' Ai t: (^) trOms, carcurate
current passing through (^) surface p:2m,
00 (^) (region 2) (^) has
Fr
g'
magneric fierd d= (^) 5i* +66., t.75,rNmin region (^) 2. rrnd d
and (^) H in region 2.
12+6) ?- (^) List
case (^) in &ee space. (^) A conducting bar (^) ean slide
conducting (^) rails placed at x (^) = 0 and x :^ lgcm.
calculate (^) the induced (^) voitage in the bar if the
and
<:
DIVERGENCE
.ARTESTAN v.D^ =
-Y:-
.YLTNDRT*AL o.,^ =|fio
q"l#+*
spHEBrcAL v-o=jflrrr,l*$$(Dpsino).##
GRADIENT
cARrEstAN on^ =#^*#r#'=
ay .Jav^ ,dY
=?ap+|"0*^" ap'u' pW^ 0z
sPHEBTcAL
on =ff,,l#**#",
CURL
.ARTESTA,N v^ x r{^ = (* -Y)",.
W-*)r.
(*
\
a.rr,.
3y
cyLrNDRrcAL v^ x^ H^ =
G#
-'#)",. (* - #)"
-!!e)"' pL (^) eip da )
spHERrcAL v^ x^ II^ =#
[,(ffl
-W)".itL,*W-ry]"
*ilvy-#7^r
LAPLACIAN
cARrEsrAN v,v^ =ff+#"#
cvLrNDHrcAr-
tr =iAffi
-*#.#
SPHERICAI.
n:i?#).h(,#) .##
TRIBHIJVA}'IUNIVERSITY
Examination
Control
Division
Exam.
ffit"l
Pass Marl$
I
80
1?
Programme
Year / Part
cs Wsas!
,"**u".esarerequiredtogivetheiranswersintheirownwordsasfaraspractica
{ (^) AnemPt$lquestio'ls'
,
'rir'iffi
in the margin^
indicate (^) fq!'-Ma*r
r (^) iiiriro*
t (^) Rurrre suitable
dataifnecessary'
I. civen
pointsA(p = 5,^
q= 7a',-z=-3)and
B (p^ 1
2'Q=;s^0" z=^
l)'find:
(a)
a unit vecro,^
m .lrt.iiun^
coordinares
at A directeil toward'B;
(b) a unit vector
tsl
.ooiainu"t at^
z. Two uniform^
line charges,^
each z^
t1 m' Find
the rotar^
.ru.oi.hio-i;;;ffi&.
surface of^
a sphere
having a^ radius
it ir.uitt'oJi'nir'
1' 0)'
e' u^ e'"r'-^ -^
t6l
Density in
electrostatic^
field'
t7l
planes 2x^
18 a-re:t
100
v and 0, respectivery.^
ro rno^
ii,rlill v^ i,^
p (5, 2, E);i)^
E at P(5,2,6)'^ I7l
S.LetafilamentalycurrentofsmAbedirectedfrominfiniwtotheoriginon
thti positive^
r.iil;;;:;b'.k;;;;";;;G
;;ih'
positive x^ axis'^
Find H^
tsl
t et^ the^
be (^5) uH/m
in regiott A
whetex<'O,.and
pHAn in
"gion
Ei*f"tu i
'
o' If^ there^
culTentdensi.ryK=150av-ZOOa'n'rmatx=0'andifHl=300a'-400a'+
lHuh
o) lH"J(";li*r'
to HNel'^
Maxwell'S equation
and inteBral
Also define^ the dispracement
;f
penetration.. [10]
s. Establish^
for Helmholtz's
equation
for electromagnetic
wave
tsl
propagation.
_ .. r- ^L--_^-
tol
prove Poynting's^
theorem'
0onalsssless
50-0 line'The
operating frequency.is^
208 MHz,ai^
ii.*uu.t.t
gth on the line^
is? rn"
(a) If
ur* ttr.'i*1i1,^
char tJ find^
the input^ impedance'
(b) whar i,^
"'i;t'dhui
ii rr,.^ distance^
the nearest voltage
t?I
11un.o-'o*orectangularwaveguidehasdimensionsa=.2cmandb=1cm.
Determine
the rangE.of
frequenci.;;;;;i;i.tt
tf'* guide^
will operate single
t3l
mode ftEro)
on:'
a) TE^ rnode^
b) Antenna^
ProPerties
TRlBHUV,4N LTNIVERSITY
Exaruination
Control
Division
--;tPt::{:Esryes*sli
Candidates are
give their answers^
in their^ own words
as^
far
AttentPt
All questions'^ "ii*is,r;; ,, t,-..r
in the ruargin^
indicar.e F$tMs'rk*
Tsun* tuitable^
duta if^ necessary^
'iirirr*, ^
tkat the^ Bortt^
Faced letter^
represents a^
vector d/?cz^ a5pr561ip
L1l
vector.
l.Findthevectorthatextendsfrom4(-3'-4'6)to8(-5'2'-8)andexpressitincylindrical (^) li+
rr :- t ''--+^'t (^) '+
+t1a
^ri(
cliarges are^ locate0 is characterized by
'nClnf
and find:-
-^
a) Dg(Tangential^
in Region 1);
t
b) Polarization^
(P1);
"j
p,, O"""al
component
il
grti*gential component of
E in^ Region 2)
Assuming,
v in^ the
cylindricai
;rr.*;r
rh* #;;;
solve the Laplace's equation by
Vf"tiroJ
uo derive^ ,ir"^
"rpt.ttion
for ihe^ capacitance^
of the Spherical
capacitor
uri,g d;;^
solution of^
v.'"^"""'"
for magnetic
in different
a co-xial
cabte carryins^
,;;if;if'iirt
iurr.d;;;;;,
I in the inner^
conductor
and -I
outer conductor'
coordinate
at P(-1'5'
ai'""ti*
on the z-axis and^
extending fi'om z=-3 ta
z=3.
and giYe^ the^
physical interpretation^
example' [1+3]
MFIz. If^ E=^
cos
(tot+By) a,/lm','t'rite
for electric and^
magnetic
" (^) fields, i.e., E,^
(x,y,z) and^ H.^
'l '"'pt"ii;"il^
ir:.;il*or forms'^
'
you,ll get^ the n
ax"i-mu*
a irrioiui'"-oi
"f""toit
held intensity^
boundary
i, at ;;th"^
,*gi"n z<0 is
p-rr* ai.lectricand
the region^
z>a may be^ of^
any
material.
!
of thc displacement
current density in^ an^ air^
--
;;;;";.f;rrr"rH=trj6cos(3?7t+i.2566x
10-62) *rNm. t6l
of 100fi' The
load voitage is +olr8"v.^
polver delivered to^
the ioad; (b)^ the
magniturie of^
the min'-rmum voltage^ on the
iine' [4+4]
of *'aveguides-when^
transmission lines?^
magnetic
modes used in rectangular waveguides'
an antenna and^ explain^
rhat you have stu t*
ofthe line is 30 pflm, (^) find: [Z+Z+2+ZJ a) Inductance of the line b) Characteristic impedance c) Phase constant at 100 MHZ d) Reflection coefficient (^) if the line is terminated
I l. What are the advantages (^) of waveguides over tansmission
' has a moss-section of 2.5 cm x^ 1.2 cm- Find the cut-off frequencies d dominant mode and TE (1,1)
l2l {:
DIVERGENCE
93 aLk
dx 0y 0z
Cylindrical: v.D =
1g*
p (^) op poq (^) oz
GRADIENT
cartesian: vv^
cyrindrical: vv
Hq+
l"#eo,
Spherical: Vv^
ffa;
i#a;
LAPLACIAN
cartesian: v2v^
azv ozv ozv
=
efr) *
CURL
Cartesian:
Cylindrical: V^ x^ H
Spherical: V^
x (^) H
==
_
e? +
_
*d< *
',.*
=200 -
j O. Find (a)^ SWR (b)^ Zu^ if^ the^ line is^ I^ m
long; (c)^ the distance from the load to the nearest voltage maximwn. 12+4+
I l. Differentiate between transmission line and waveguide. A rectangular waveguide having
I. Calculate the cut-off frequency^ of the dominant mode.^ t4+
CARTESIAN
CYLINDRICAL
SPHERICAL
AxfuAz
uobr).;#"#
v.o=.!(,,o-\n-
I a('illD').-:
-rt rsin9 Ag rsin90$
CARTESIAN
CYI,INDRICAT-
r;Pt iliRtcAL
0v" av^
-a
r+
oy (^) -a_oz
tav^ aY-
+-a_
pod' oz
raY^ |^ av^ L--^ .L--n
r O0"o rsin? 0,1"c
At/
=+a,
ox
^ vy (^) --d
cp
av"
or
cARrEsrAN
""
=(+-+),,.(+
T)r,"(*-+)^,
cylrNDRrcn L vzH (^) =(1an' -a!t\u
.{9!--gg-.)a..rf
a('?H')
-9!r)u.
\p
ad oz )""
' a" ap )"' pl op
a )
cARTESTAN s'e,^ =g'{ot{ *Ef,
&2 avz 022
cYLTNDRTcAL ,', -Lg( o{)-+.
Pop\
op) p-^ o9- oz-
spHERrcAL v,^ a (^) =--L-lu(u::"') -l?'iu. .:{^
Lary--g('l)la"
rsingl a0 A )
'
rlsind d/ dr )
r{a(,n,1 afl. ).
r[ 0r A0)'
spFrERrcAL o,o (^) =Ig(,'91)-f -1[.r9] *^ .]--!
,' 0r\ dr (^) ) ,'^ sin9^ dd^ A0^ ) r'sin"^0 0Q'
Yli
gS| :
Y""tt |rylre*1tig-(W
o:)
{ (^) Candidates are required to give^ their^ answers^
in their ouryt^ words^ as^
far as practicable'
/ (^) Auempt 4ll questions"
{ (^) Thefigures in the margin indicate^ Full^
Matr*s'
t
i.uu..rp, anci i,,r,"aprdenotes a unit vector
along the^ direction
gru"i ty the subsript.
necessary.
.*-: pelirr.
by an expression
i=#(""-vi,*'i.),transformthisvectorincylindricalcoordinate
system at^ point^
Given the flux^ density^ fr =12ccs0lr';a.+(sin0/13)au
Clm2,evaluate both^ sides^
1r^ (^) , It
defrned by I^ <^ r <2.^
<0 <-,0
(Region 2) has lrr
= i0. if there is a uniform^ magnetic^ freid^
i=S{+e{+ 7i,Al^in
region l,find Band Hinregion2. [2+3+3]
a metallic conductor at 60 Hz, if
)+
€=€qrp=p0,6=5.8x107S/m, and^
j
=sin(37?t (^) -117.12\a*MA/m2- t5]
ll+sl
Is+3]
?
t dD1-, dDy , dD V.U=--a=:t;
Cylindrical:
Cylindrical:
0x 0Y 0z vfi-1a(PDpr+1999+ry Y'v-p aP (^) Pa oz -R td(rzD , t altT-9De)- 1 dDO V. D^ = A a, -;trs- ao- - i"o aO w= T,q;# T" w= fri#6##ao Laplacian Gradient
Curl v,v=#+#+# cyrindricar: vzv =;*(r#) .if"+#
iV#) . #(sino#) .
v xE^
-T)a
*)d
#)
;(ry
#)a v x^ n^ == ;k(ry
H)d
iffiH
@)a
i(ry-')'; s ** " 22 TzuBHUVAN UNIVERSITY
vector components. Examinatio n Control Division i.t:gry j-.PE]:-!!x:IJf i (^) :' M"'k' j* 2072 chaitr"^ 'if:lgr!--ini{-- (^) ir'g'---._j 3 }
. iflf1-ili{-- (^) ir'1r'---..i
3 hrs'- ---:--- : ------_j:ryr;t r"--*;eps"cle1telp"$ ----':- r' carrdidates are required to give their answers in^ their own rn'ords as^ iar^ as^ practicable' { (^) Anempt Att questions' / (^) Th"
in the margin indicate Full-Mstk' / (^) Neieisary tables are attached^ herewith' { /r"prurent
io,o.*p, denotes a^ unit vector along the^ direction given by the subscriPt. / Assume suitable data if necessary' freld i=sa. in^ (a)^ cylindrical^ components
[2+3]
A .+- Derive the expression^ for the^ electric freld intensity due^ to^ an^ infrnitely long line^ charge with uniform "t -g" density p,^ by^ using Gauss's law.^
of 20 nClmis located^
at y (^) =3 and z=5^ ' Find^ E at P(5'6'1) [4+4] Derive an expression^
due to a^ dipole^ in^ terms of the dipole
/-r++++ moment (^) f ol o dipole for^ which^ p=3a*-5a'+10a"nC'm
/
[4+4] (1,2,-4). Find E at^ P. Assuming that the potential v^ in^ the^ cylindrical coordinate system^
solve the Lapplace's equution and derive the^ expression^
of coaxial capacitor of iengtn^ f.^ using the
same solution^ of^ V. Assume the inner conductor^ of radiUs ;;;;t"ttt"i iir trt t"ip to the conductor of radius b'^ t6l
the^ closed^ line integral of^ H
(5,4,i)to Pr(5,6'1)to Pr(0,6,1)to Po(0,4,1)to P,^ using straight^ line segments' if
potential^ and show^
[1+3+4] equation. Given the vector magnetic^ potential i=-(Ot t+)i,WAtm,^ calculate the total^ magrretic flux crossingtle surface^ 4:n/Z'