SUMMARY
·
Like charges repel and unlike charges attract
·
The total charge in the universe is conserved
·
Charge is quantized. Total charge in an object q = ne where n =
0,1,2,3… and e is electron charge.
· Coulomb’s law in vector form: (r ^ is unit vector along joining q1, q2)
·
For continuous charge distributions, integration methods can be
used.
·
Electrostatic force obeys the superposition principle.
·
Electric field at a distance r from a point charge:
·
Electric field lines starts at apositive charge and end at a
negative charge or at infinity
·
Electric field due to electric dipole at points on the axial line
:
· Electric field due to electric dipole at points on the equatorial line:
· Torque experienced by a dipole in a uniform electric field:
· Electrostatic potential at a distance r from the point charge:
· Electrostatic potential due to an electric dipole:
·
The electrostatic potential is the same at all points on an
equipotential surface.
·
The relation between electric field and electrostatic potential:
·
Electrostatic potential energy for system of charges is equal to
the work done to arrange the charges in the given configuration.
·
Electrostatic potential energy stored in a dipole system in a
uniform electric field:
·
The total electric flux through a closed surface : ΦE =
Q/ε0 where Q is the net charge enclosed by the surface
·
Electric field due to a charged infinite wire :
·
Electric field due to a charged infinite plane :
· Electric field inside a charged spherical shell is zero. For points outside:
·
Electric field inside a conductor is zero. The electric field at
the surface of the conductor is normal to the surface and has magnitude E = σ/ε0
.
·
The surface of the conductor has the same potential, at all points
on the surface.
·
Conductor can be charged using the process of induction.
·
A dielectric or insulator has no free electrons. When an electric
field is applied, the dielectric is polarised.
·
Capacitance is given by C = Q/V .
·
Capacitance of a parallel plate capacitor: C = εA / d
·
Electrostatic energy stored in a capacitor: U = 1/2 CV2
·
The equivalent capacitance for parallel combination is equal to
the sum of individual capacitance of capacitors.
·
For a series combination: The inverse of equivalent capacitance is
equal to sum of inverse of individual capacitances of capacitors.
·
The distribution of charges in the conductors depends on the shape
of conductor. For sharper edge, the surface charge density is greater. This
principle is used in the lightning arrestor
·
To create a large potential difference, a Van de Graaff generator
is used
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