### The Concept Of Electric Field

**Concepts to remember on the concept of the electric field for JEE and CBSE board exams:**

**Electric field:**

- A region around a charged particle or object where its influence can be felt.
- Its direction is from positive to negative charges.
- It has both magnitude and direction that’s why it is a vector quantity.

**Electric field lines:**

- Imaginary lines that represent the direction and strength of the electric field.
- The closer the lines, the stronger the field.
- Electric field lines start from positive charges and end at negative charges.

**Electric field strength (E):**

- Force experienced by a positive test charge placed at a point divided by the magnitude of the test charge.
- The unit is Newton/Colomb (N/C).

**Point charge:**

- A particle with a nonzero electric charge.
- It is considered to have a charge concentrated at a single point in space.

**Coulomb’s Law:**

- The force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them.
- The equation is F = k * q1 * q2 / r2
- Where k is the electrostatic force constant (k= 9 x 109 Nm2/C2), q1 and q2 are the magnitudes of the charges, and r is the distance between them.

**Superposition Principle:**

- The net electric field at a point due to multiple point charges is a vector sum of the individual electric field due to each charge.

**Electric field due to a point charge:**

- Radially outward from the positive charge and radially inward for the negative charge.
- The magnitude of the electric field due to a point charge is given by E = k * q / r2
- Where E is the electric field, k is the electrostatic constant, q is the magnitude of the point charge, and r is the distance from the point charge.

**Electric field inside a conductor:**

- The net electric field inside a conductor in electrostatic equilibrium is always zero.
- Conductive materials allow free charge movement, so charges redistribute to cancel out any net electric field.

**Electric field on the surface of a conductor:**

- The electric field just outside a conductor in electrostatic equilibrium is perpendicular to the surface at every point.
- Charges arrange themselves to cancel the electric field within the conductor, resulting in a perpendicular field.

**Electric Field Due to a Charged Sphere**

- The electric field due to a charged sphere is exactly the same as that of a point charge of with the same charge located at the center of the sphere.
- The charges are distributed uniformly on the surface of the sphere.