# MCQs on Electromagnetic Fields

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01․ The electric field on a plane is decribed by . The field due to
a dipole and a monopole.
a monopole.
a dipole.
none of above.

The above expression shows that the dipole field varies as (1/r)2 and the monopole field varies as (1/r). Hence, the field produces due to the presence of both dipole and monopole.

02․ Electric field inside a hollow metallic charged sphere is
increasing towards centre.
decreasing towards centre.
zero.
none of above.

Inside a hollow metallic charged sphere, that will not allow the outside electric field because of the charge separation of electrons and holes at the surface of sphere and creating an equal and opposite field. Hence, the electric field inside a hollow metallic charged sphere is zero.

03․ Unit of electric flux density is
coulomb.
coulomb / meter2.
weber / meter2.

We know that the tube forces radiating from a charged body, which are also referred as electric flux, is equal to the total charge of the body. The amount of radiating electric flux through the unit surface area is known as electric flux density. Hence, the unit of electric flux density is coulombs / m2. As the unit of charge is coulomb.

04․ The number of Faraday tubes of flux passing through a surface in an electric field is called
electric charge density.
electric field intensity.
electric flux.
magnetic flux density.

The tubes of flux passing per unit area through a medium are supposed to be the electric displacement of that that dielectric medium. In this case, they referred to as the electric flux. The lines of flux are called Maxwell.

05․ Electric intensity at any point in an electric field is equal to the ___________ at that point.
electric flux.
magnetic flux density.
none of them.

The total electric field at any point is equal to the vector sum of the separate electric fields that each point charge would create in the absence of the others. That is,
The electric field is nothing but the potential gradient of that particular point.

06․ The energy stored in the magnetic field in a solenoid 10 cm long and 4 cm diameter wound with 2000 turns of wire carrying a current at 20 amp, is
24 joules.
12 joules.
30 joules.
15 joules.

07․ Two coils have inductances L1 = 1200 mH and L2 = 800 mH. They are connected in such a way that flux in the two coils aid each other and inductance is measured to be 2500 mH, then Mutual inductance between the coils is ___________ mH.
225.
250.
150.
145.

Flux in two coils aid each other inductor of the combination So, the mutual inductance is 250 mH.

08․ 1 Tesla =
1 wb- m2.
1 wb/ m2.
1 wb .
1 wb/m.

Tesla is the unit of flux density, it is defined as flux flow per unit area. So, 1 Tesla = 1 wb / m2

09․ The magnetic field required to reduce the residual magnetism to zero is called
Coercivity.
Retentivity.
Hysteresis.
Saturation magnetism.

From the B-H, the amount of magnetic field required to remove the residual magnetism is called Coercivity.

10․ The magnetism left in the iron after exciting field has been removed is known as
permeance.
residual magnetism.
susceptance.
reluctance.

Whenever we apply the exciting field continuously to one coil, there is a chance that some magnetic power is left in that coil for a particular time even if we remove the applied exciting field. This left over magnetic power is called residual magnetism.

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