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Coulomb's Law - Practice Questions & MCQ
Edited By admin | Updated on Sep 18, 2023 18:34 AM | #JEE Main
Quick Facts
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Coulomb's Law is considered one the most difficult concept.
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69 Questions around this concept.
Solve by difficulty
Two identical charged spheres suspended from a common point by two massless strings of length are initially a distance
apart because of their mutual repulsion. The charge begins to leak from both spheres at a constant rate. As a result, the charges approach each other with a velocity
. Then the relation between v and x is:
A charge Q is placed at each of the opposite corners of a square. A charge q is placed at each of the other two corners. If the net electrical force on Q is zero, then the Q/q equals
Two spherical conductors B and C having equal radii and carrying equal charges in them repel each other with a force F when kept apart at some distance.A third spherical conductor having same radius as that of B but uncharged is brought in contact with B then brought in contact with C and finally removed away from both, The new force of repulsion between B and C is :
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Two charges and
are placed in vacuum at a distance
and the force acting between them is
. If a medium of dielectric constant 4 is introduced around them, the force now will be:
A pendulum bob of mass and carrying a charge is at rest in a horizontal uniform electric field of 20000 V/m. The tension in the thread of the pendulum is ( g = 10 m/s2) :
In the given figure two tiny conducting balls of identical mass m and identical charge hang from non-conducting threads of equal length L. Assume that
is so small that, then for equilibrium
is equal to
Concepts Covered - 1
Coulomb's Law
Coulomb's Law: The force of attraction or repulsion between two charges is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them.
K = Proportionality Constant
and
are two Point charges
In SI unit value of K is
Where,
known as absolute permittivity of air or free space
The vector form of Coulomb's Law:
Consider two charges and
separated by a distance r. Let the position vectors of
be
and that of
be
. Then the force due to
on
as shown in figure
is directed along the unit vector
and
Force when dielectric inserted between the charges:
When a dielectric of dielectric constant k is completely filled between the charges then force
is relative permittivity / dielectric constant of the medium. The dielectric constant is the ratio of the permittivity of a substance to the permittivity of free space. (dielectric will be explained later in detail in this chapter)
If the dielectric of thickness d is partially filled between the charges then
Principle of Superposition:
It states that the total force acting on a given charge due to a number of charges is the Vector sum of the individual forces acting on that charge due to all the charges.
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