1. The problem statement, all variables and given/known data A positively charged particle moves in a circle of radius R in the plane of the page with velocity v when a magnetic field B is into the page. (a) If the magnetic field is increased, will the speed of the charged particle remain the same increase, or decrease? 2. Relevant equations 3. The attempt at a solution I just have a problem which is the direction of the velocity I should take.. this problem is number 13 in this site http://www.wellesley.edu/Physics/phyllisflemingphysics/106_p_induction.html, and it's solution is here http://www.wellesley.edu/Physics/phyllisflemingphysics/106_s_induction.html I didn't understood how to take the sense of v (clock wise or counterclock wise)...hope someone clarify.thanks.