Electrostatics :- Very Short answer type questions

Question 1: Define following terms

(a) Dielectric constant of a medium
(b) Electric dipole moment
(c) Electric flux
Answer 1:
(a)It is the ratio of the capacitance (Cr) of a capacitor with dielectric between the plates to the capacitance (Cr) of the same capacitor with vacuum between the plates i.e. K=Cr/C0
(b) It is the product of the magnitude of one of the point charges constitting the dipole ant the distance of separation between two point charges.
(c) Electric flux through an area is the product of the magnitude of the area and the component of electric field vector normal to this area element.
Electric flux = E.ds
SI unit of flux is NC1m2

Question 2: Electric field inside a dielectric decreases when it is placed in an external field. Give reason to support this statement.
Answer 2: An electric field EP is induced inside the dielectric in a direction opposite to the direction of external electric field E0. Thus net field becomes
E=E0-EP

Question 3: Electric field lines can not be discontinuous. Give reason.
Answer 3: Electric field lines can not be discontinous because if they are discontinous then it will indicate the absence of electric field at the break point.

Question 4: Why do electric field lines can never cross each other?
Answer 4: It is so because if they cross each other then at the point of intersection there will be two tangents which is not possible.

Question 5: What is the net amount of charge on a charged capacitor?

Answer 5: The net charge of a charged capacitor is zero because the charges on its two plates are equal in number and opposite in sign. Even when the capacitor is discharged net charge of the capacitor remains zero because then each plate has zero charge.

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