Electric field is an electrical property associated with each point in space where a charge is present in any form. The magnitude and direction is expressed by the value of E. In an equation, E refers to the electric field strength or electric field intensity. The value of the electric field at a point is required to assess what may happen to electric charges close to that particular point.
Measuring the Electric Field
One must not consider the electric force as the direct interaction of two electric charges at a distance from each other. Where one charge is the source that extends outward into the surrounding space. Whereas, the force exerted on a second charge in this space acts as a direct interaction between the electric field and the second charge. The strength of an electric field E is defined as the electric or Coulomb. And force F exerted per unit positive electric charge q at that point. These get expressed as E = F/q. If the second charge is greater in magnitude, the resultant force is doubled. However, the measure of the electric field E, remains the same at any given point. The strength of the electric field depends on the source charge, not on the test charge. Strictly speaking, the introduction of a small test charge, which itself has an electric field, slightly modifies the existing field. The electric field may be thought of as the force per unit positive charge. This force gets exerted before the field is disturbed by the presence of the test charge.
Calculating the magnitude of Energy
The direction of the force that is exerted on a negative charge is opposite that which is exerted on a positive charge. An electric field has both magnitude and direction. So, the direction of the force on a positive charge is chosen arbitrarily as the direction of the electric field. Because positive charges repel each other, the electric field around an isolated positive charge is oriented radially outward. When they get represented by lines of force, or field lines, electric fields start on positive charges and terminating on negative charges. A line tangent to a field line indicates the direction of the electric field at that point. Where the field lines are close together, the electric field is stronger than where they are farther apart. The magnitude of the electric field around an electric charge is considered as source of the electric field. This depends on how the charge gets distributed in space. For a charge concentrated nearly at a point, the electric field is directly proportional to the amount of charge. Therefore, it is inversely proportional to the square of the distance radially away from the center of the source charge. The presence of a material medium always diminishes the electric field below the value it has in a vacuum.
Unit of measurement
It is a vector quantity denoting that it possesses both magnitude and direction. As we know, the value of E, is also known as electric field strength or electric field intensity. E is represented by the equation;
f = force acting in newtons and q = charge in coulombs.
The value of the electric field has dimensions of force per unit charge. In the metre-kilogram-second and SI systems, often used units are newtons per coulomb, equivalent to volts per meter. In the centimetre-gram-second system, the electric field is signified in units of dynes per electrostatic unit (esu), equivalent to stat volts per centimeter.