# EC2253 Electromagnetic Fields Important Questions

Unit I

1.Derive the expression for electric Field on the axis at a point h m of a uniformly charged circular disc

of radius a m with a charge density of ?s c/m2

2. Find the electric field intensity of a straight uniformly charged wire of length Lm and having a linear

charge density of +? C/m at any point at a distance of h m

3. State and Prove Gausss law. List the limitations of Gausss law.

4. Find the magnetic field density at appoint on the axis of a circular loop of a radius b that carries a

current I

5 Explain coulombs Law .three equal positive charges of 4X 10-9 coulomb each are located at three

corners of a square ,side 20cm.determine the electric field intensity at the vacant corner point of the

square.

Unit II

1.Circular disc of radius a is uniformly charged with a charge density of s c/m2. Find the electric field

intensity at a point h from the disc along its central axis

2. Derive an expression for magnetic field strength, H, due to a current carrying conductor of finite

length placed along the y- axis, at a point P in x-z plane and r distant from the origin.

3. Derive the expression for the E at a point P due to an electric dipole.

4. Find the magnetic field intensity at the centre O of a square loop of sides equal to 5M and carrying

10A of current

Unit III

1.Solve the laplaces equation for the potential field in the hompogenousregion between the two

concentric conducting spheres with radius a and b where b>a V=0 at r = b and V =V0 at r=a .find the

capacitance between the two concentric spheres.

2.Determine the inductance of a solenoid of 2500 turns wound uniformly over a length of 0.25m on a

cylindrical paper tube , 4 cm in diameter .the medium is air

3. A cylindrical capacitor consists of an inner conductor of radius a and an outer conductor of radius b.

The space between the conductors filled with a dielectric whose permittivity e, the length of the

capacitor is L. Determine the capacitance

4.Derive an expression for the inductance of solenoid

5.Show that the inductance of the cable L = μl/2p (ln b/a) H.

6.Derive an expression for the capacitance of a spherical capacitor with conducting shells of radius a

and b.

Unit IV

1.Solve one dimensional Laplaces equation to obtain the field inside a parallel plate capacitor and

also find the surface charge density at two plates

2.State and prove Poynting theorem.

3.Derive Maxwells equation derived from Faradays law both inIntegral and point forms

4. Three capacitors of 10,25 and 50 microfarads are connected in series and parallel. Find the

equivalent capacitance and energy stored in each case ,when the combination is connected across a

500 V supply

5.Derive modified form of Amperes circuital law in Integral and differential forms

Unit V

1.Derive the expression for the reflection by a perfect dielectric –normal incidence

2.Obtain the wave equation for a conducting medium

3.Derive the wave equation starting form Maxwells equation for free space For good dielectrics derive

the expressions for a, ß, ? and ?.

4. Find a, ß, ? and ?. for Ferrite at 10GHz er = 9, μr = 4, s = 10 ms/m

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