**Electrostatic Field Questions And Answers**

*What is the***Electrostatics:**It is branch of physics it is also deals with the study of charges at re electricity It is also known as**static electricity or or frictional electricity***What is the**Frictional Electricity:**Frictional electricity is the electricity produced by rubbing together with two bodies of different substances*.*What is the***Electric Charge:**Electric charge is defined as a basic and characteristic property elementary particles of matter in terms of which certain forces and interaction energies may be defined. Electric charge is an Intrinsic property

au of the elementary particles like electrons, protons etc. of which all the objects are made up*What is the***Quantization of Charge:**The quantization of charge means that charge can exist only as integral multiple of electronic charge i.e. q = ±ne, where n is an integer. It was first suggested by Faraday.

5. *What is the**Charge Conservation***:** In an isolated system, the total net charge of the system always remains constant.

*What is the*.**Charge is transferable:**If a charged body is in contact with an uncharged body, it becomes charged due to transfer of electrons from one body to another*What is the***Charge**is always associated with mass Charge can not exist without mass though mass can be exist without charge.*What is the***Additivity of charge:**Total charge of a system is the algebraic sum of all individual charges in the system.*What is the**What is the***Charge is invariant:**Charge is independent of the frame of reference.*What is the***Coulomb’s Law**: Coulomb’s law states that the magnitude of the electric force between two charges is directiy proportional to the product of the magnitude of the charges and inversely proportional to the square of the distance between them and acts along the line joining between two charges*What is the***Fundamental law of electrostatics**: It state that, “Like charges repel and unlike charges attract each other”.*What is the***Methods of charging :**There are three methods of charging a body by

(i) Friction

(ii) Induction

(iii) Conduction.*What is the***Continuous Charge Distribution: lt has three types,**

(i) Linear charge distribution: Charge is distributed along a line (One dimensional distribution).

(ii) Superficial charge distribution: Charge is distributed over a surface (two dimensional distribution).

(iii) Cubical charge distribution: Charge is distributed over a volume (three dimensional distribution.)*What is the***Electric Field**: Electric field due to a given charge is defined as the modified space around the charge in which electrostatic force of attraction/repulsion due to the charge may be experienced by any other rest charge. The S.I. unit of electric field is NC-1*What is the*ri**Electric Lines of Force**: It is locus of the test charge within an elect*c field.**What is the***Properties of electric lines of force**

(i) It starts from positive charge and ends at negative charge.

(ii) If there is a single charge, they may start or end at infinity.

(iii) For single charge, electric lines of force are straight and for two charges they are continuous smooth curves without any break.

(iv) Electric lines of force never intersect each other.

(V) Electric lines of force do not form closed loops. So they are discontinuous.

(vi) Electric lines of force starts or ends normally on the surface of a conductor.

(vii) Electric lines of force never pass through conductor. So they do not exist inside a conductor, Because clectric field inside a conductor is zero.

(viii) Electric lines of force are closer when field is stronger and spread out when field is weaker.

(ix) For uniform electric field electric lines of force are equidistant, parallel straight lines.

(x) It exerts lateral pressure or tendency to expand laterally. Hence, like charges repel.

(xi) Electric lines of force have a tendency to contract lengthwise. Hence, unlike charges attract.

(xiii) The tangent to a lines of force at any point

gives the direction of the electric field at that point,*What is the***Electric Dipole :**A pair of equal and opposite point charges separated by a very small distance constitutes an electric dipole.*What is the***Electric Dipole Moment :**The electric dipole moment of an electric dipole is given by the product of one of the two charges constituting the dipole and the vector distance between them. It is a vector quantity and its direction is from negative charge to the positive charge.*What is the***Torque on an electric dipole:**Electric Dipole moment may be defined as the torque acting on an electric dipole, placed perpendicular to a uniform electric field of unit

strength.**Mathematically, T = PE sin ∅**

It E =1 unit, ∅ = 90°, then, t = P*What is the***Electric Potential Electric potential**at a point in an electric field is defined (or measured) as the quantity of work done in moving a unit positive test charge from infinity to that point against the electrostatic force of repulsion. It is a scalar quantity and its S.I. unit is volt (V).*What is the***Potential Difference**: Electric potential difference between two points in an electric field is defined (or measured) as the quantity of work done in moving a unit positive test charge from one point to other.*What is the***Equipotential Surface:**Equipotential surface is a surface obtained by joining all the points in an electric field having same electric potential.*What is the***Properties of equipotential surfaces**(i) Two equipotential surfaces or lines never intersect with each other.

(ii)Work done on moving a charge on an equipotential surface is zero.

(iii) Electric field is always normal to the equipotential surface at every point.

(iv) Equipotential surfaces are closer together and farther apart in the regions of strong field and weak field respectively.*What is the***The electrical potential energy of a charge**q at a point in an electriic field due to charge q is the amount of work done in moving the test charge q from infinity to that point.*What is the***Basic electrostatic properties of a conductor:**

(I)Inside a conductor,electric field is zero.**(**ii) At the surface of a charged conductor**,**electric field must be normal to the surface at every point.

(iii) Within the conductor, there is no excess change in the static situation.

(iv) Electric potential is constant throughout the volume of the conductor and has the same value (as inside) on its surface.

(v) Electric field at the surface of a charged conductor is £= ⁰/£⁰ñ

where o = surface charge density and ñ = unit vector normal to the surface in the outward direction.*What is the***Electric Flux:**Electric flux through a given area is defined as the total number of electric field lines passing through that area normally.*What is the***Gauss Theorem (Law) in Electrostatics Gauss’s theorem (law)**states that the total electric flux through a closed surface is equal to**1/E⁰**times the net charge enclosed by the surface, where E is the permittivity of vacuum or free space.

*What is the***Application of Gauss’s theorem:**Electric field due to a uniformly charged infinite plane sheet**is E = o/2£ō****Where E= electric field intensity, o = surface charge density.***What is***Solid Angle:**Solid angle is defined as the ratio of the area of the surface of the portion of a sphere enclosed by the conical surface forming the angle to the square of the radius of the sphere. It is 4π steradian about a point.**What is****Relative Permittivity/Dielectric Constant:**Relative permittivity or dielectric constant is defined as the ratio of the electrostatic force between two charges separated by a distance in vacuum to the electrostatic force between the same two charges separated by the same distance in that medium. It is also known as Specific Inductive Capacity (SIC).*What is***Capacitance**: Capacitance of a conductor may be defined as the ratio of charges given to a conductor and the resulting potential developed on it when it is completely isolated. Its S.I. unit is farad (F).**What is****Capacitor :**A capacitor or condenser is a device that stores electric charge.it consists of two conductors separated by an insulator or dielectric. The two conductors

carry equal and opposite charges

Q. The symbol of capacitors are

**(a) Fixed capacitance(b) Variable capacitance**

**What is the****Grouping of capacitors**When capacitors are connected in series, the net capacitance of the combination decreases. In this case the charge through each capacitor is same. When capacitors are connected in parallel, the net capacitance of the combination increases. In this case the potential difference (P.D.) across each capacitor is same.**What is the****Dielectrics :**Dielectrics are the substances which donot conduct an electric charge but allow inductive influence to take place through them n an electric field, e.g. : Glass, Porcelain, Mica,Polyethene, Paper, Air, Wax, Wood, Rubber,Plastic etc.

(i) Non-polar dielectrics: If the centres of Positive and negative charges of the molecules of a dielectric exactly coincide with one another under normal conditions

the dielectric is said to be non-polar, e.g.H², N², O², etc.

(ii) Polar Dielectrics: In molecules of polar dielectrics the centres of positive and negative charges do not coincide with one another and remain separated even under normal conditions e.g. : H²O and HCI.

**What is the****Polarisation of the dielectric :**Both polar and non-polar dielectrics developed a net dipole moment in the presence of an external electric field. This fact is called polarisation of the dielectric. Polarisation of dielectric reduces the electric ficld inside the dielectric.

**What is the****Permittivity :**Permittivity of a dielectric medium is a measure of its response to external electric field.**What is the****Electron Volt:**It is the energy gained by an electron as it moves through a potential difference of 1 volt in an electric field.**What is the****Gaussian Surface:**It is an naginary surface enclosing the charge or, charge ribution. It is of any shape and size.**What is the****Ideal Electric Dipole:**An electric dipole of whose magnitude of charge tends to infinity and separation tends to zero is called Ideal Electric Dipole.**What is the****Potential Gradient:**The rate of change of potential with distance at a point is called potential gradient.**What is the****Principle of Capacitor:**The capacitance of a conductor gets increased greatly, when an earth conductor is placed near it.

**42 What are Uses of capacitor:**

(i) In radio circuits for tuning.

(ii) To produce electric field of desiredpatterns.

(iii) In the tank circuit of oscillators.

(iv) For producing rotating magnetic fields in Esossa induction motors.

(v) In power supplies for smoothening the rectified current.

(vi) They store not only charge, but also energy in the electric field between their plates.

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