Why potential energy alone, not kinetic energy?

[logearav]

Homework Statement

My physics textbook on the topic " Electrostatics" says, charges have force acting on them, so they possesses potential energy. My question is " Why potential energy alone, not kinetic energy?"

Homework Equations

The Attempt at a Solution

 

[irishbob]

Well it's electroSTATIC, so the charge isn't moving. Electrostatic force is exerted by stationary particles.

To answer your question more broadly:

Imagine a particle is placed into an electric field, and held in equilibrium by some force. Stop time, and remove the force holding it in equilibrium. In this particular instant, the particle possesses potential energy alone. The moment it starts moving, it loses potential and gains kinetic.

 

[Rockstar3143]

Can anyone explain me y bulging effect is there at the sides of the two parallel plates of different potentials.. Why Elecric lines of force at the sides are curved?

 

[X-rays]

I have one question on electrostatic force.We say that when a glass rod is rubbed on silk cloth,electrons from glass are transferred to silk. Hence glas rod becomes positively charged and the latter negatively charged. But i wonder,can a little amount of friction make electrons to get transferred from glass to silk?What actually happens in the above example.And one more question is that,when we move barefeet on a carpet and then touch a metal door knob,we experience a mild shock.How does this happen?explain please.

 

[Gauhar Rajput]

My question is the same as X-rays has asked above. . .

 

[Sefrez]

Can anyone explain me y bulging effect is there at the sides of the two parallel plates of different potentials.. Why Elecric lines of force at the sides are curved?

The only reason the field lines are uniform nearer the center of two parallel plates is because they are the net result of the combined electric fields from all particles on the plates surface. You see this when using calculus to derive these fields.

At the edges of the plates (the reality where we do not have infinitely long plates) you don't have surrounding electric fields that create this uniform field. The electric field quickly drops off with distance (from each particle: E = q/4∏εr^2.) Also notice that if a plate is finite in size, then there always exists some distance away from it that it could be considered a single particle.