Continuous Charge Distribution – Class 12 | Chapter – 1 | Physics Short Notes Series PDF for NEET & JEE

Continuous Charge Distribution: A continuous charge distribution refers to the distribution of charge in a system where the charge is not located at discrete points, but is instead spread out continuously over a region of space. The charge density, which is the amount of charge per unit volume, can vary over the region, but the total charge in the system is obtained by integrating the charge density over the entire region.

The electric field produced by a continuous charge distribution can be calculated using Gauss’s law, which states that the flux of the electric field through a closed surface is proportional to the charge enclosed within the surface. Using this law, it is possible to calculate the electric field produced by a continuous charge distribution for any point in space.

Examples of Continuous Charge Distribution

Examples of continuous charge distributions include charged rods, spheres, and disks, as well as charged continuous media such as solids and liquids. In each case, the charge density depends on the geometry of the system and the distribution of charge within it.

Calculation of Continuous Charge Distribution

To calculate the electric field and potential due to a continuous charge distribution, you can use Gauss’s law and the concept of electric potential energy. Here’s an overview of the steps involved in the calculation:

  • Determine the charge density: The first step is to determine the charge density of the continuous charge distribution. The charge density is the amount of charge per unit volume and is a function of the position within the system.
  • Calculate the electric field using Gauss’s law: Gauss’s law states that the flux of the electric field through a closed surface is proportional to the charge enclosed within the surface. To calculate the electric field due to a continuous charge distribution, you need to find the flux of the electric field through a closed surface surrounding the charge distribution and equate it to the charge enclosed within the surface.
  • Calculate the electric potential using electric potential energy: Electric potential energy is the amount of work required to bring a unit positive charge from an infinite distance to a point in the electric field. To calculate the electric potential due to a continuous charge distribution, you need to integrate the electric field over the path taken by the charge from an infinite distance to the point of interest.
  • Solve for the electric field and potential using mathematical techniques: Depending on the specific case, you may need to use mathematical techniques such as calculus and coordinate systems to solve for the electric field and potential. For example, in the case of a charged sphere, you may need to use spherical coordinates and the formula for the electric field and potential due to a point charge to find the electric field and potential due to the continuous charge distribution.

Formula of Continuous Charge Distribution

There are several formulas that can be used to calculate the electric field and potential due to a continuous charge distribution. Some of the most common formulas are:

  • Electric field due to a charged rod: The electric field due to a charged rod of length “L” and linear charge density “λ” (charge per unit length) at a point “P” a distance “r” from the center of the rod can be calculated using the following formula:

    E = (k * λ * L) / (2 * r2)

    where “k” is Coulomb’s constant.

  • Electric field due to a charged sphere: The electric field due to a charged sphere of radius “R” and charge “Q” at a point “P” a distance “r” from the center of the sphere can be calculated using the following formula:

    E = k * Q / r2

    where “k” is Coulomb’s constant.

  • Electric potential due to a charged sphere: The electric potential due to a charged sphere of radius “R” and charge “Q” at a point “P” a distance “r” from the center of the sphere can be calculated using the following formula:

    V = k * Q / r

    where “k” is Coulomb’s constant.

  • Electric field due to a charged disk: The electric field due to a charged disk of radius “R” and surface charge density “σ” (charge per unit area) at a point “P” a distance “r” from the center of the disk can be calculated using the following formula:

    E = k * σ / r

    where “k” is Coulomb’s constant.

  • Electric potential due to a charged disk: The electric potential due to a charged disk of radius “R” and surface charge density “σ” (charge per unit area) at a point “P” a distance “r” from the center of the disk can be calculated using the following formula:

    V = k * σ * ln(r/R)

    where “k” is Coulomb’s constant and “ln” is the natural logarithm.


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By Team Learning Mantras