Chapter 16, Problem 23Q

Consider a small positive test charge located on an electric field line at some point, such as point P in Fig. 16—32a. Is the direction of the velocity and/or acceleration of the test charge along this line? Discuss.

To determine

Whether the field line at the point P in the given figure gives the direction of velocity/acceleration of a test charge placed at the point P.

Answer to Problem 23Q

Solution:

The direction of velocity/acceleration of a test charge placed at a point in an electric field is given by the direction of field line at that point.

Explanation of Solution

Since the only force acting on the test charge is electric, the direction of field line at the point P gives the direction of electric force on the test charge. The direction of acceleration of a particle is always in the direction of force acting on the particle as per Newton’s second law of motion. So, the field line at the point P gives the direction of velocity/acceleration of the test charge placed at the point P.