a charge particle is free to move in an electric field ....what kind of path it wil travel...with respect to the line of force?????

Question

anonymous · Answer

The force on a charged particle is from an electric field
$F=qE\cos(\theta)$

Lets consider two extreme cases. First lets see what happens if the angle between the electric field and the velocity vector is zero - they both point in the same direction - $\theta = 0$:
$F=qE\cos(0)=qE$
since $\cos(0) = 1$. This means that a force equal to $qE$ is exerted in the same direction it is going - it will accelerate.

Now lets see what happens when the particle is moving in the opposite direction to the electric field, or $\theta = 180$.
$F=qE\cos(0)=-qE$
since $\cos(180) = -1$. This means that a force equal to $qE$ is exerted in the opposite direction it is going - it will decelerate.

You can see this in this picture