Question

Electric Field Activity By the end of this activity you will be able to do the following: • Recognize correct and incorrect features in electric field lines • Qualitatively sketch field lines for a charge distribution. • Qualitatively sketch the motion of a charge given the field lines. 1. General Features of electric field lines Electric field lines are a way of repre- senting the electric field. There are three rules for drawing these lines: • At each point Ē is tangent to the field lines. . The magnitude of E is proportional to the density of field lines (i.e. to the number of field lines in a fixed area). • They go away from positive charges and toward negative charges, or they start on positives and end on negatives. Explain why these are sensible rules, given that the electric field is the force divided by the test charge.

Answer 1

Electric field. due to a point chargo: 1. In order to calculate Ê due to charge a, consider a - test charge q. at a distance x or from the charge a: 1 Force acting on a due to a is F = kQq 92 . È at a due to a will be Ē AR E a for positive charge it. Qyo direction of field vectors are radially outward while for negative charge, - re, aco the direction of field rectors are radially inword.

Electric field Lines: Electric field lines are the pictorial representation of the electric field produced by the electric charge. Scientist Michael faraday introduced the concept of electric field lines and obtained important results of electric field. - "An electric field line is a curre drawn in an electric field in such a way that the tangent to the curre at any point is in the direction. of net electric field at that point." 1. In fact, an electric field is the path along which a positive charge would more if free to do so. . Now, we consider an example of electric dipole to understand the method of drawing electric field liner

We can use the equation of electric field to ... determine the intensity PAVEL of electric field at any point. As shown in fig., draw a rector of electric A field CÊ ) at a boint P, according to magnitude and direction of electric field at that point. Now consider another point p' close to e and draw a rector of electric field E z at that point according to its magnitude & direction. Similarly, draw ă vector Ez at point p", very close to e' same way other vectors of electric field can be drawn. - P. pl,p" all these points are so close to each other that a continuous curre passes through the tails of these rectors can be doawn. This Curre represents the electric field line. Thus the curre on which the tangents are drawn at different points like P, P',P",... and so on, represent the direction of È at the respective points, is called Ě field lines

- Characteristics of Electric field lines: (1.) Electric field lines start from - the charge and end at ove charge (2) The tangent drawn at any points on the electric field lines shows - the direction of electric field at that point. (3) Two field lines never crom each other. 1. If two lines intersect . at a point, two tangenta can be drawn at that / Y È point indicating two directions of È at that boint which is not posible (4) Electric field lines of stationary electric charge distribution do not foom closed loops .

(5) The seperation of neighbouring field lines in a region at electric field indicates the strength of electric field in. That riegion... . . 9n bractice, the number of field lines are so restricted that the number of field lines passing through unit crom sectional area about a point , kept berpendicular to electric field lines in proportional to the intensity of electric field at that point of the field lines are close to each other, the electric field in that region in relatively strong, if the field lines are far apart, the field is weak in that region.