Sunday, March 26, 2017

Neutral Point and Equilibrium of Electric charge in a line Video Lesson

Electrically  neutral point is a location at which the resultant electric force is zero. It means the charge kept at that point is experiencing equal and opposite force due to the other two charges kept in that line. To find the neutral point, we can equate the two forces and when the two charges are of similar nature, we can get null point between the charges existing in one line and beyond them, we are not going to find the neutral point. At a location beyond the neutral point, the force acting on the third charge are in the same direction and hence there will  not be any neutral point. It is explained in the following video lesson and the location of neutral point is also derived.

Neutral Point between opposite charges

When the charges are of opposite nature, the resultant force on a third charge in between them is not zero and it is experiencing the two force in the same directions. If we consider a location out side the two charges and consider a third charge, it experience forces due to two charges in opposite direction. If they are equal in magnitude, we can get null point as shown in the video lesson. The expression for the location of null point is also derived here.

Equilibrium of system of three charges

Now we are considering a scenario of three charges kept on a straight line. If the two charges at the ends of the line, we can get null point between them weather we keep positive or negative charges in between them. But to keep any of the positive charge at the end of the system, we shall only keep a negative charge but not positive charge in between them. Thus to keep system of three charges in equilibrium, we need to keep two positive charges at the ends and a negative charge in between. We need to write the conditions  for zero resultant force location in at least on two charges so that we can get the magnitude,location and nature of the charge in between to get the answer as shown in the video lesson below.

Finding separation between two charges suspended from rigid support

Let us consider two identical ball of same mass and similar charge kept suspended from a rigid support using a light wire and because of the repulsion there will be some angular as well as physical separation between them. We need to find that angular separation in terms of the given data and the video solution is as shown below.

Motion of Charged particle in Electric Field

Let us consider a charged particle is moving horizontally with some constant velocity and an electric field is applied perpendicular to the motion. Gravitational force is small and we can ignore it in this case. Thus there is no force in the horizontal direction and hence the charged particle will have constant velocity over the horizontal direction. 

There is no initial velocity along the vertical direction but there is electric force due to intensity along the Y axis. Thus the particle experience acceleration along Y axis and hence the velocity of the particle increases on that axis. We can find the final velocity along each direction and its displacement along both the axes. It is further shown in the video lesson that the path of the charged particle is parabola as shown below.

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