00:01
Question we have to find the direction of magnetic field b vector for the three situations as per the question and we have a positive charge particle that is charge particle is plus q so now for the better understandment of this problem let us consider some convention so let us suppose the right direction is i cap and so we get left direction it will be minus i cap okay and up direction is plus j cap or down direction it will be minus j cap and the inward direction inward it will be suppose minus k cap so the upward to the plane or we can say that outward it can be called as or better outward so outward is plus k cap okay so these are the convention taken for this better announcement of this question.
00:59
So now for the part a in which we have some directions, so we can draw it as per the question.
01:06
So it is our problem.
01:09
So in which we have this vector fb, and we have velocity vector pointing in this right direction.
01:17
So this is velocity vector and this is magnetic force vector.
01:22
So since we know that from the lawrence law, the magnetic force, fb vector, it is given by q v vector multiplied by b vector.
01:32
This is velocity vector and this is magnetic field vector.
01:36
So from these conventions we can write that fb which is in the upward direction means j cap.
01:43
So we can write that fbj cap.
01:46
This will be equals to charge q multiplied by velocity v and direction is i cap because it is in the right side direction.
01:53
So i cap cross cross b and b cap.
02:00
We have to determine this direction.
02:03
So from the rule of vectors, we can identify that to obtain j cap and for the multiplication with i cap, so the b cap direction must be, this b cap must be equals to minus k cap.
02:19
So minus k cap means inward.
02:22
So, we get in this equation in the part a, the magnetic field will be cross, that is inward to the plane...