(2) (a) Find the potential difference between a point located a distance r from

Question

(2) (a) Find the potential difference between a point located a distance r from a positive point charge, +q, located at the origin and a point located very far away.

(b) Find the potential difference between a point located a distance r away from a positive point charge, +q, located at a point R away from the origin in the x-direction.

(c) Imagine a situation where both these charges exist. Describe the surface where the total potential is zero.

(d) Describe the surface where the total electric field is zero.

Explanation / Answer

a) the potential at a distance r from a point

charge q

V = k q / r ( k = 1/ 4 pai epsilon zero )

And by principle we know that potential at a point very far away is taken as at infinity and potential is zero .

The difference in potential of two points is the potential difference

So pd = k q /r - 0 = k q / r

b ) potential difference between two points is the difference in potential of two points.

P d = k q /r - k q /R

= k q ( 1/ r - 1/ R )

c ) Total potential at a point due to a system of charges is given by addition of the potential due to individual charges

So the total potential will be zero at point very far away from both the charges .

d ) electric field at a point is the force experienced by a unit positive charge placed at that point .

Since both the charges are positive , the field will be zero at the point midway between the point charges on the line joining them .

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