Three equal charges +Q each are at the corners of an equilateral triangle as shown. The intensity of electric field at O will be

Hint: Electric field is defined as a physical force on a point which is exerted by a charge. The field lines move outwards from a positive charge while move inwards for a negative charge. It can be considered as a loop of flow from positive charge to negative charge. For equally distant charges, the electric field intensity at an equally distant point is always the same. Use this information to find the intensity of the electric field at O.

Complete answer:
It is given that the three charges have +Q charge each. As their charge is the same, the magnitude of intensity produced by each charge at O will also be the same. Now, it is given that the triangle is an equilateral triangle, so their angles will also be the same i.e.120°.

The force exerted by each charge on O will also be the same. As the charges are positive, the direction of the electric field would be outwards and towards the midpoint of the opposite lines as shown in the figure above. Now, as the magnitude of electric field intensity remains the same for all the charges, the three vectors form a triad. We know that the electric fields in the form of triads cancel each other.
Thus, the intensity of the electric field at O will be zero.

Note:
To solve this kind of question, students must have clear understanding and knowledge of electrostatics. Students must remember that if the charge is positive then the force acts in the direction of the electric field. If the charge is negative then the force acts in the opposite direction of the electric field. A charge placed in an electric field experiences a force whether it is moving or is at rest.