Electric Fields And Charges Flashcards
Quantisation of Charge:
The total charge on a body is the integral multiple of fundamental
charge’e’
The dielectric constant
The dielectric constant of a medium is defined as
the ratio of permitivity of medium to the permitivity of free space, i., K = ele
1 C
1 coulomb charge is the charge which when placed at a distance of 1 metre from an equal and similar charge in vacuum (or air) will repel it with a force of 9 x 10° N.
Principle of Superposition of Electric Charges
Coulomb’s law gives the force between two point charges. But if there are a number of interacting charges, then the force on a particular charge may be found by the principle of superposition. It states that
Electric field
The electric field strength at any point in an electric field is a vector quantity whose magnitude is equal to the force acting on a unit positive test charge and the direction is along the direction of force.
Properties of electric field lines
2) Field lines start from positive charges and end at negative charges. If there is a single charge, they may start or end at infinity.
(2) In a charge-free region, electric field lines can be taken to be continuous curves without any breaks.
(i) No two electric field lines can intersect each other because if they do so, then two tangents can be drawn at the point of intersection; which would mean two directions of electric field strength at one point and that is impossible.
(iv) The electric field lines do not form any closed loops. This follows from the conservative nature
of electric field.
(v) The equidistant electric field lines represent uniform electric field while electric field lines at different separations represent non-uniform electric field (Figure).
Electric field lines
An electric field line is a curve drawn in such a way that tangent to it at each point is in the direction of the net field at that point.
Electric dipole
A system containing two equal and opposite charges separated by a finite distance is called an electric dipole. Dipole moment of electric dipole having charges +q and - q at separation 2l is defined as the product of magnitude of one of the charges and shortest distance between them.
Electric flux
The total number of electric field lines crossing (or diverging) a surface normally is called electric flux.
Electric flux through surface element dS is 4ф = E.d$ = E dS cos 0, where E is electric field strength.
Gauss theorem
It states that the total electric flux through a closed surface is equal to 1/€ times the net charge enclosed by the surface
