CONCEPTUAL QUESTIONSANDNUMERICAL EXAMPLES INPHYSICS : CONCEPTUAL QUESTIONSANDNUMERICAL EXAMPLES INPHYSICS ELECTROSTATICS
BY KAJAL SENGUPTA
PART-II : PART-II GAUSS’S THEOREM
AND
APPLICATIONS
PART- I : PART- I ELECTRIC FIELD
AND
ELECTRIC POTENTIAL
ASSUMED PREVIOUS KNOWLEDGE : ASSUMED PREVIOUS KNOWLEDGE The questions and examples are based on following theoretical concepts:
DEFINITION OF ELECTRIC FIELD
FIELD DUE TO POINT CHARGE
LINES OF FORCE IN ELECTRIC FIELD
ELETRIC POTENTIAL ENERGY AND POTENTIAL
POTENTIAL DUE TO A POINT CHARGE
POTENTIAL DUE TO DIPOLE
ELECTRIC FIELD DUE TO A DIPOLE
Theoretical derivations of formulae are not being taken up
Important concepts : Important concepts Electric field produced by a charge does not exert force on the charge producing it.
Lines of force are purely imaginary . They give a qualitative idea about the electric field. They do not exist physically.
When a conductor is placed in an electric field the net field inside is zero due to redistribution of charge. Applying Gauss’s theorem we conclude that the net charge is zero. Its not the other way round
Contd…… : Contd…… Electric potential describes the field
Potential is defined at a point whereas potential difference is between two points
Two definitions of potential: potential at a point due to a charge is the work done in bringing unit positive charge from infinity upto the point
or, potential at a point is the work done by an external agent in bringing unit test charge from reference point upto the point without changing the kinetic energy
Some questions based on the above concepts : Some questions based on the above concepts Number of lines of force is 2?. How do you explain this?
For a conductor placed in electric field, is the charge inside zero? What happens to the free electrons in the conductor?
How do you keep the kinetic energy unchanged when you are bringing the test charge near another charge?
How is infinity related to the reference point?
In the definition of potential there are two charges involved. Potential is due to which of them?
Some more….. : Some more….. What is the relation between work done in bringing a charge from one point to another and potential difference between them?
What is the relation between VA and VB for (i) positive ‘q’ (ii) negative ‘q’ ? q A B
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