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Electrostatic Potential Energy - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #JEE Main

Quick Facts

  • Electrostatic Potential energy is considered one of the most asked concept.

  • 62 Questions around this concept.

Solve by difficulty

In free space, a particle A of charge 1μC is held fixed at a point P. Another particle B of the same charge and mass of 4μ kg is kept at a distance of 1 mm from P. If B is released, then its velocity at a distance of 9 mm from P is:

[ Take 14πϵ0=9×109Nm2C−2]
 

Two equal charges q are placed at a distance of 2a  and a third charge -q  is placed at the midpoint. The potential energy of the system is :

If a person brings an electron towards another electron then the change in potential energy of the entire system will be

When a charged particle is placed in uniform electric field its momentum is p. If the mass of particle is doubled, then the momentum of particle will become:

Consider an initially neutral hollow conducting spherical shell with an inner radius r and an outer radius of 2r. A point charge +Q is now placed inside the shell at a distance r/2 from the center. The shell is then grounded by connecting the outer surface to the earth. P is an external point at a distance of 2r from the point charge +Q on the line passing through the center and the point charge +Q as shown in the figure.

 

The magnitude of the force on a test charge +q placed at P will be 

One can define alpha-Volt (aV) to be the energy acquired by a a particle when it is accelerated by a potential of 1 Volt. For this problem, you may take a proton to be 2000 times heavier than an electron. Then:

A molecule with a dipole moment p is placed in an electric field of strength E. Initially the dipole is aligned parallel to the field. If the dipole is to be rotated to be anti-parallel to the field, the work required to be done by an external agency is

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Concepts Covered - 1

Electrostatic Potential energy

Electrostatic Potential energy -

It is the amount of work done by external forces in bringing a body from  âˆž  to a given point against electric force.

or It is defined as negative work done by the electric force in bringing a body from  âˆž  to that point.

  • - It is Scalar quantity
    - SI Unit: Joule
    - Dimension: [ML2T−2]

Electric Potential energy at a point

If the point charge Q is producing the electric field

Then electric force on test charge q at a distance r from Q is given by F=KQqr2
And the amount of work done by the electric force in bringing a test charge from ∞ to r is given by

W=∫∞rKQqx2dx=−KQqr


And negative of this work done is equal to electric potential energy

 So U=KQqr

U→ electric potential energy
r→ distance between two
Change of potential energy-
if a charge q is moved from r1 to r2 in a electric field produced by charge Q
Then Change of potential energy is given as

ΔU=KQq[1r2−1r1]

ΔU→ change of energy
r1,r2→ distances
Potential Energy Of System Of two Charge-

U=KQ1Q2r(S.I)where K=14πϵ0
 

   Potential Energy For a system of 3 charges-

U=K(Q1Q2r12+Q2Q3r23+Q1Q3r13)


Work energy relation-

W=Uf−Ui


Where W= work done by an external force

Uf− final P.E Ui− initial P.E. 


The relation between Potential and Potential energy-

U=KQqr=q[KQr] As  But =KQr


So U=qV
Or potential is defined as Potential energy Per unit charge.

 i.e V=WQ=UQ


Where V→ Potential
U→ Potential energy
Electron Volt-

1ev=1.6×10−19 J=1.6×10−12erg
 

It is the smallest practical unit of energy which is used in atomic and nuclear physics.

Electric potential Energy of Uniformly charged sphere-

U=3Q220πϵ0R


Where R - Radius and Q - total charge.
Energy density- It is defined as the energy stored for unit volume.

Uv=UV


Where U− Potential Energy and V− Volume.

 

 

 

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Electrostatic Potential energy

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