Questions about electrostatic potential energy. a. The relation U = qV is often
ID: 1864211 • Letter: Q
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Questions about electrostatic potential energy.
a. The relation U = qV is often interpreted as follows: If a point charge q is
placed at a point where the potential due to other charges is V, the point charge q acquires potential energy U = qV . Explain why this is wrong.
b. If V = 0 at infinite distance, then a system of charges that has total energy (kinetic plus potential) greater than zero is unbound. Explain why.
c. One can describe the total potential energy of a system of charges either as (1) the work done by an agent to bring the charges in from infinite distance and place them at rest at their final locations, or, (2) the negative of the work done by electrostatic forces while the system is being assembled. Explain why these give the same result.
Questions about electrostatic potential energy. a. The relation u-qV is often interpreted as follows: If a point charge q is placed at a point where the potential due to other charges is V, the point charge q acquires potential energy u-qV. Explain why this is wrong b.If V 0 at infinite distance, then a system of charges that has total energy (kinetic plus potential) greater than zero is unbound. Explain why One can describe the total potential energy of a system of charges either as (1) the work done by an agent to bring the charges in from infinite distance and place them at rest at their final locations, or, (2) the negative of the work done by electrostatic forces while the system is being assembled. Explain why these give the same result. C.Explanation / Answer
(a)
U=q. (delta V) is correct rather than U=q.V .
Because at V=0 i.e. at infinity;
By, U=q.V , U= 0 but actually it is not .
When a charge particle moves from a finite point to infinite point or from a potential to zero potential (high to low) then because of this positive change in potential, that charge particle has some energy that is equal to the work done by us(+ve) to bring the particle to infinity.
(b) As i said above, work done to bring charge partical to infinity is stored with the partical as total energy i.e. greater than zero.
(c) When we bring particle from infinity to a specific point then we have to do work. Because particle comes from low potential to high potential that is only possible when work is done by us. So basically we have to do work in both the cases either to bring back many particles from infinty or to assemble any charge body by bringing charges from infinity(or non specific point). So both are same thing and equivalent to each other, Negative and equal in magniude.
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