- Electric Field Intensity Definition: Electric field intensity is defined as the force acting on a unit positive charge within an electric field.
- Coulomb’s Law: Coulomb’s law describes the force between two charges based on their magnitudes and the distance between them.
- Calculation of Electric Field: The electric field strength at a point is determined by the force on a unit positive charge at that point.
- Units and Vector Nature: Electric field strength is measured in Newtons per Coulomb (N/C) and is a vector quantity, meaning it has direction.
- Resultant Electric Field: The total electric field strength at a point with multiple charges is found by adding up the individual field strengths vectorially.
Electric field strength or electric field intensity is the synonym of electric field. Electric field strength can be determined by Coulomb’s law. According to this law, the force ‘F’ between two point charges having charge Q1 and Q2 Coulombs and placed at a distance d meter from each other is given by,
Here, εo is the permittivity of vacuum = 8.854 × 10 – 12 F/m and εr is the relative permittivity of the surrounding medium.
Now, let us put Q2 = + 1 Coulomb and let us denote force F by E in the equation (1), and by doing these we get,
This equation shows the force acting the a unit positive charge placed at a distance d from charge Q1.
As per definition, this is nothing but of electric field strength of charge Q1 at a distance d from that charge. Now, we got the expression of electric field strength or intensity. Now, by combining this expression with equation (1), we get,
The above expression shows that, if we place a charge at any point in an electric field, the product of the electric field strength at that point and the charge of the body gives the force acting on the body at that point in the field. The above expression can also be rewritten as,
Based on this expression, the electric field strength can be expressed in Newtons per Coulomb (N/C). Since electric field strength has direction, it is a vector quantity. Intensity refers to the magnitude or amount. Therefore, electric field intensity means the magnitude of the field’s strength. In summary, electric field intensity or strength is written as:
We have discussed electric field intensity at a point due to a single charge. However, if the point is influenced by multiple charges, we must first calculate the electric field strength at that point for each charge. Then, we vectorially add all the field strengths to find the resultant field strength at that point.
