1. Two spheres A and B of exactly same mass are given equal positive and negative charges respectively. Their masses after charging ?

mass of A < mass of B

remains unaffected

mass of A > mass of B

Nothing can be said

Answer: mass of A < mass of B

Explanation:

As the question states metallic conductors, only electrons move for gaining or losing charges. Also, the net excess of electrons is responsible for negative charge. Thus, A must have lost electrons and B must have gained them. Hence, Mass of A < Mass of B.


2. If a linear isotropic dielectric is placed in an electric field of strength E, then the polarization P is ?

directly proportional to E

directly proportional to E

inversely proportional to E

independent of E

Answer: directly proportional to E

Explanation:

If a linear isotropic dielectric is placed in an electric field of strength E, then the polarization P is directly proportional to E.


3. If the flux of the electric field through a closed surface is zero, then ?

the charge in the vicinity of the surface must be zero

the charge inside the surface must be zero

the electric field must be zero everywhere on the surface

the electric field may not be zero everywhere on the surface

Answer: the charge inside the surface must be zero

Explanation:

Using Gauss's law the flux of the electric field through closed surface So if the electric field is zero everywhere, then the flux may be zero. if charge inside the closed surface is zero, then flux must be zero


4. Corona discharge is caused by ?

Charges moving into the ionized air under the effect of this electric field.

Ionization of gas molecules due to dielectric breakdown

All of the above

High charge density causing high electric fields near a metal’s surface.

Answer: All of the above

Explanation:

A corona discharge takes place when there is dielectric breakdown around a conductor with high electric field.electrical discharge caused by the ionization of a fluid such as air surrounding a conductor carrying a high voltage.


5. When a comb rubbed with dry hair attracts pieces of paper. This is because the ?

comb induces a net dipole moment perpendicular to the direction of field

comb polarizes the piece of paper

electric field due to the comb is uniform

comb induces a net dipole moment opposite to the direction of field

Answer: comb polarizes the piece of paper

Explanation:

Firstly, when the comb is used to rub dry hair, it always acquires a negative charge or electron which the hair carries, where the comb is induced with the electron gotten from the hair then immediately the comb which is negatively charged comes in contact with the piece of paper which is gets polarized by the comb, there is therefore bound to be attraction between them. This therefore explains unlike charges attracting each other. Because there is an opposite charge to that of the paper. The law of electrostatics holds that unlike charges attract and like charges repel. The answer is comb polarizes the piece of paper.


6. When a body is charged by induction, then the body ?

does not lose any charge

loses part of the charge on it

becomes neutral

loses whole of the charge on it

Answer: does not lose any charge

Explanation:

The part of the body nearer to the source charge gets induced charges, opposite in nature to the source charge while the other part gets those of similar nature. Thus, no loss of charge.


7. SI unit of permittivity of free space is ?

C^2N^-1 m^-2

Farad

C^2N^-1 m^-1

Weber

Answer: C2N-1 m-2

Explanation:

Coulombic force between two charges is given by F=1/4?€ (q'.q?/r²) From here, the SI UNIT of permittivity comes out is = coulomb²/Newton-meter² C²/N-m²


8. A body is positively charged, it implies that ?

negative charge is displaced from its position

there is only positive charge in the body.

there is equal positive and negative charge in the body but the positive charge lies in the outer regions

there is positive as well as negative charge in the body but the positive charge is more than negative charge

Answer: there is positive as well as negative charge in the body but the positive charge is more than negative charge

Explanation:

An object is positively charged if it has an deficiency of electrons, and is otherwise negatively charged or uncharged.


9. Two point charges + Q and + q are separated by a certain distance. If + Q > + q then in between the charges the electric field is zero at a point ?

no where on the line segment joining + Q and + q.

exactly at the mid-point of line segment joining + Q and + q.

closer to + q

closer to + Q

Answer: closer to + q

Explanation:

Two point charges + Q and + q are separated by a certain distance. If + Q > + q then in between the charges the electric field is zero at a point closer to + q.


10. Positive electric flux indicates that electric lines of force are directed ?

inwards

either (a) or (b)

outwards

None of these

Answer: outwards

Explanation:

Positive electric flux is due to + charge. So, lines of force are directed outwards.