Question

Two point charges q and -2q are kept d distance apart. Find the location of the point relative
to charge q at which potential due to this system of charges is zero.

Answer 1

Explanation:

location of the point related to the charge Q at which potential due to the system of charges is zero is at d/3.

Answer 2

Answer:

Explanation:

There are two points where potential is zero.

Case 1 :- q --------------•A--------- -2q

Let A is the point where potential is zero.

Let distance between q and -2q = r

and distance between q and A = x

∴ distance between -2q and A = (r - x)

Potential at A = Kq/x + K(-2q)/(r - x)

⇒0 = k[ q/x - 2q/(r - x) ]

⇒1/x = 2/(r - x)

⇒r - x = 2x

⇒ r/3 = x

Hence, potential is zero at x = r/3

Case 2 :- q---------------------- -2q ----------• B

let B is the point where potential is zero.

Let distance between -2q and B = x

∴ distance between q and B = (r + x)

Now, potential at B = kq/(r + x) + k(-2q)/x

⇒0 = kq/(r + x) - 2kq/x

⇒1/(r + x) = 2/x

⇒ x = 2r + 2x

⇒ x = -r but x is distance so, x ≠ -r

Case 3 :- C ----------q------------------ -2q

distance between q and C = x

∴ distance between -2q and C = (r + x)

Now, potential = kq/x - 2kq/(r + x)

⇒0 = 1/x - 2/(r + x)

⇒1/x = 2/(r + x)

⇒2x = r + x

⇒x = r

Hence at x = r potential will be zero.

So, there are two points