How to determine direction of magnetic field using cross product. Share with your friends Share 0 Sanjay Singh answered this Dear student Let us define a vector c→=a→×b→Now direction of vector c→is perpendicular to both the vectors a→ and b→ or we can say that it is perpendicular to the the plane formed by the vectors a→ and b→Now there are two directions which are pperpendicular to the plane formed by vector a→ and b→ one directed up the plane and the other directed down the plane.To decide weather the vector c→ is up the plane or down the plane we can use two methodsM :1 Right hand screw rule:Hold the screw with the right hand keeping its length perpendicular to the plane formed by the vector a→ and b→ and rotate it from the first vector towards the other vector through the smaller angle between the vectors than the screw will move either up the plane or down the plane .The direction of the vector c→ is in the direction of advancement of the screw.M 2: Right hand thumb rule Place your palm on the plane formed by vector a→ and b→ keeping the palm perpendicular to the plane of vector a→ and b→ keeping the thumb perpendicular to the forefingers and let your forefingers face the first vector of the cross product that is a→and rotate the forefingers to the other vector through the smaller angle between the vectors than the direction of the thumb point in the directio of the vector c→.Regards -1 View Full Answer Simranpreet Singh answered this If you are talking about Bio-Savart's law, then according to it, , so, current element cross the distance of it from the point of observation gives u the direction of magnetic field. 0
, so, current element cross the distance of it from the point of observation gives u the direction of magnetic field.