Electric Field Question?!
Consider a small positive test charge located on an electric field line at some point. Is the direction of the velocity and/or acceleration of the test charge along this line? Explain.
At first I thought that the velocity would be on the line, while the acceleration would be tangent to the line, but now I am not so sure. Can someone explain this to me?
The direction of electric force at any point on a field line is along the tangent at that point. A test charge at any point in the field experiences is a force which is a tangent to the field line at that point. This means the direction of the acceleration experienced is also along the tangent at the point (F=ma). If the line changes direction, so do the force and acceleration.
However, in general the velocity is NOT along a field line. It depends on the particle's previous motion, If a particle was initially accelerated along a straight field line and the field lines suddenly curved, the particle's momentum would mean that its new velocity was not along the new field lines.