In the region where the density of these lines is low, the electric field has lower strength. This means that electric field strength due to the charged body is more in the region where the density of field lines is high. The magnitude of the field is indicated by the density of the lines.The relative spacing between lines provides an indication of the electric field strength at that point. Field-line in general is a curve drawn in such a way that the tangent to it at each point in the direction of the net field at that point.ĭefinition: An electric field line is an imaginary line or curve drawn over an empty space region such that its tangent at each position, points in the direction of the electric field vector at this position.An electric field line is an imaginary line drawn in such a way that its direction at any point is the same as the direction of the field at that point.Connecting up these vectors to form a line is a nice way to represent the electric field.Since the electric field varies as the inverse of the square of the distance that points from the charge the vector gets shorter as you go away from the origin and they always point radially outwards.Now to get a feel of this field one can sketch a few representative vectors as shown in fig below It was Faraday's understanding that the pattern of lines describing the electric field is an invisible reality.įor a single positive point charge q, the electric field is given by relation The notion of the electrical field was first presented by the 19th-century physicist Michael Faraday. The illustration shows a two charge system containining equal positive and negative charges.Let us now learn about field lines which are a pictorial representation or way to imagine electric fields. Lines of force (field lines) start on positive charges and end on negative charges. The number of lines of force per unit area is proportional to the electric field. The electric field is strongest close to the central charge, and this is where the lines of force are densest. They are a very useful way of visualising the electric field. These lines, representing the direction of the electric field are called lines of force. On the other hand for an isolated negative point charge the force on the test charge is in the opposite direction, and so the field is directed towards the centre. Since at every point the electric field is a vector, it is called a vector field.įor an isolated positive point charge the force on a positive test charge is directed away from the centre, and so the field is also directed away from the centre. The electric field at the test point is the vector sum of the field from charge 1 and the field from charge 2. Showing that electric field is additive in the same way as electric force. Since the force is a vector, the electric field is also a vector.Īs seen in the previous section, electrostatic forces are additive, and add vectorially.Īnd since the test charge q is common to all terms in the summation it can be divided out The units of the electric field are N C –1, or V m –1. The field does not depend on the test charge, since according to Coulomb's law F is proportional to q. The electric field at a point may be defined as the electrostatic force that would act on a test charge placed at that point divided by the charge of the test charge. The idea that a charge interacts with the electric field surrounding the other charges in the system is a very useful tool for visualising the electrostatic forces. 19th century scientists found the idea of action at a distance very disturbing, and the concept of an electric field extending into the space surrounding charges was first proposed by Michael Faraday. No prior knowledge is assumed.Ĭoulomb's electrostatic force is operates between charges even in a vacuum. Level 0 (green)- this is basic material that you have probably encountered already, although the approach may be slightly different.
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