Solved Exercise/Numericals - Electrostatic Energy & Energy Density.



Q.1 Point charges Q1 = 1 nC, Q2 = -2 nC and Q3 = 3 nC and are positioned one at a time and in that order at (0, 0, 0), (1, 0, 0) and (0, 0, -1) respectively. Calculate the energy in the system after each charge is positioned?
Ans:

Initially the system is assumed to be charge free.

The energy required to bring Q1 into the system is 0 J.

After Q1: Energy in the system = 0 J

The energy required to bring Q2 into the system is


Hence, After Q2: Energy in the system = -18 nJ

The energy required to bring Q3 into the system is:

W3 = Q3 ( V31 + V32 ) + Q2 V21


Q2. Determine the work necessary to transfer charges Q1 = 1 mC and Q2 = -2 mC from infinity to points (-2, 6, 1) and (3, -4, 0) respectively.
Ans:

No work is done in transferring the first charge Q1. However work done to transfer the point charge Q2 is given as:




Q3. A point charge Q is placed at the origin. Calculate the energy stored in region r > a?
Ans:

Work done in assembling a volume charge distribution in terms of electric field and flux density is given as:



Electric field intensity due to a point charge Q placed at origin is given as:


Hence energy stored in a region r > a is given as:




ALSO READ: 

- Gauss's Law - Theory.

- Gauss's Law - Application To a Point charge.

- Gauss's Law - Application To An Infinite Line Charge.

- Gauss's Law - Application To An Infinite Sheet Charge.

- Gauss's Law - Application To a Uniformly Charged Sphere.

- Numericals / Solved Examples - Gauss's Law.

- Scalar Electric Potential / Electrostatic Potential (V).

- Relationship Between Electric Field Intensity (E) and Electrostatic Potential (V).

- Electric Potential Due To a Circular Disk.

- Electric Dipole.

- Numericals / Solved Examples - Electric Potential and Electric Dipole.

- Energy Density In Electrostatic Field / Work Done To Assemble Charges.

- Numericals / Solved Examples - Electrostatic Energy and Energy Density.

- Numericals / Solved Examples - Gauss's law...



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Comments

  1. UnknownApril 11, 2010 at 10:12 PM

    lightening is an example of static electricity how can we prove?

    ReplyDelete
  2. UnknownApril 11, 2010 at 10:16 PM

    very very very fiiiiiiiiiii9 sir

    ReplyDelete

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