Friday, May 8, 2009

1. E L E C T R O S T A T I C S .3M ANSWERS,

1. E L E C T R O S T A T I C S .3M ANSWERS,
1. DEFINE ELECTRIC LINES OF FORCE.
The concept of field lines was introduced by Michael Faraday as
an aid in visualizing electric and magnetic fields.
Electric line of force is an imaginary straight or curved path along
which a unit positive charge tends to move in an electric field.
2. STATE THE PROPERTIES OF ELECTRIC LINES OF FORCE.
(i) Lines of force start from positive charge and terminate at negative
charge.
(ii) Lines of force never intersect.
(iii) The tangent to a line of force at any point gives the direction of
the electric field (E) at that point.
(iv) The number of lines per unit area, through a plane at right angles
to the lines, is proportional to the magnitude of E. This means
that, where the lines of force are close together, E is large and
where they are far apart, E is small.
(v) Each unit positive charge gives rise to 1 εo lines of force in free
space. Hence number of lines of force originating from a point
charge q is N =q ε in free space.
3. DEFINE ELECTRIC DIPOLE.GIVE EXAMPLES.
Two equal and opposite charges separated by a very small distance
constitute an electric dipole. Water, ammonia, carbon−dioxide and
chloroform molecules are some examples of permanent electric dipoles
4. DEFINE DIPOLE MOMENT.WRITE EXPRESSION,UNIT.
The magnitude of the dipole moment is given by the product of the
magnitude of the one of the charges and the distance between
them. Electric dipole moment, p = q2d or 2qd. It is a vector quantity
and acts from –q to +q. The unit of dipole moment is C m.
5. DEFINE TORQUE EXPERIENCED BY ELECTRIC DIPOLE?
The magnitude of torque is,
τ = One of the forces x perpendicular distance between the forces
= F x 2d sin θ = qE x 2d sin θ = pE sin θ (q × 2d = P)
Note : If the dipole is placed in a non−uniform electric field at an
angle θ, in addition to a torque, it also experiences a force.

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