The image below is of a charged moving in a uniform magnetic field. Is the particle positively or negatively charged? Solution According to Fleming left hand rule, When the thumb,first finger,middle finger are streatched perpendicular to each other and the first finger represents the magnetic field direction ,middle finger represents the direction of motion of positive charged particle then the thumb represents force on charged particle. In figure , magnetic field into the paper and the particle deflect right.So, the charged particle is negative nature.