A magnetic field is said to exist at a point if a force is
Answer Details
A magnetic field is said to exist at a point if a force is exerted on a moving charge at the point. A magnetic field is created by a magnet or by the movement of electric charges, such as in a current-carrying wire. When a charged particle moves through a magnetic field, it experiences a force perpendicular to both the direction of motion and the direction of the magnetic field. This force is what causes the particle to change its direction of motion, and is what we refer to as a magnetic force. So, the correct option is "exerted on a moving charge at the point".