Question

3 equal charges (all +Q) are located at A, B and C. ABC is an equilateral triangle with sides d. Point A is located at (0,0), point B at (d,0), point C at (d/2,d3√/2). Point P is inside the triangle such that AP=BP=CP. What is the electric field at P - we want the magnitude and the direction.
@rajathsbhat

Answer 1

OK here's the situation:
let's isolate the triangle

Answer 2

Now I'll try to explain to you why the field at P is 0 because of symmetry.
Suppose, the field at P is non-zero.
Then, it should have a direction. Let the direction be something like
Now, I turn the triangle by 120 degrees in the counter-clockwise direction.

Notice how it is now exactly like it was in the previous situation. Since the triangle was turned, the field would also have turned:
Now, compare the two triangles: red and green. The arrangement of the charges is exactly the same. Yet, they have different directions for the net field.
Therefore, by the argument of symmetry, we can reason that the field at point P MUST be 0.
(notice that if it's zero, there's no difference between the rotated triangles)

Answer 3

hmm thank u for good explntion

Answer 4

yw