Jawaharlal Nehru Technological University Kakinada 2008 B.Tech Electrical and Electronics Engineering ELECTROMAGNETIC FIELDS - Question Paper

Code No: 07A3EC04 Set No. 1
II B.Tech I Semester Regular Examinations, November 2008
ELECTROMAGNETIC FIELDS
( Common to Electrical & Electronic Engineering and Electronics & Control
Engineering)
Time: three hours Max Marks: 80
ans any 5 ques.
All ques. carry equal marks
? ? ? ? ?
1. (a) State and discuss Gauss‘s legal regulations.
(b) 4 concentrated charges Q1 = 0.3  c, Q2 = 0.2 c, Q3 = -0.3 c, Q4 = 0.2
c are located at the vertices of a plane rectangle. The length of rectangle is
5 cm and breadth of the rectangle is two cm. obtain the magnitude and direction
of resulting force on Q1. [6+10]
2. (a) Derive an expression for the electric ?eld intensity due to an in?nite length
line charge along the z-axis at an arbitrary point Q (x, y, z).
(b) A charge of -0.3C is located at A (25, -30, 15) Cm and a 2nd charge of
0.5  C is located at B (-10, 8, 12) Cm. obtain the electric ?eld strength, E at:
i. The origin and
ii. Point P (15, 20, 50) cm. [8+8]
3. (a) discuss duality ranging from D and J
(b) obtain the total current in a circular conductor of radius four mm if the current
density varies according to J = 104
r
A/m2
. [6+10]
4. A steady current of 10 A is established in a long straight hollow aluminum conductor
having inner and outer radius of 1.5 cm and three cm respectively. obtain the value of
B as function of radius. Also de?ne the legal regulations used. [16]
5. (a) Show that the ?eld strength at the end of a long solenoid is 1 - half of that
at the centre.
(b) obtain an expression for ?eld intensity at the centre of a circular wire carrying
a current I in the anticlockwise direction. The radius of circle is ‘r’ and the
wire in the x - y plane. [16]
6. (a) Derive an expression for force on a current element in a magnetic ?eld.
(b) If a point charge of four coulombs moves with a velocity of 5ux +6uy -7uz m/s,
?nd the force exerted, if the ?ux density is 5ux + 7uy + 9uz wb/m2
. [8+8]
7. (a) Derive an expression for mutual inductance use Newmann’s formulae.
(b) Current in a coil is increased from zero to 15 amps at a uniform rate in 6
seconds. It is obtained that this coil develops self induced emf of 150 volts
whereas an emf of 25 volt is produced in a neighbouring coil. calculate self
inductance of the ?rst coil and the mutual inductance ranging from the 2 coils.
[8+8]
1 of 2Code No: 07A3EC04 Set No. 1
8. (a) explain the physical interpretation of Maxwell’s equations.
(b) A parallel plate capacitor with plate area of five cm2
and plate separation of 3mm

Earning:   Approval pending.