A uniform magnetic field exists in the plane of paper pointing from left to right as shown in figure......

A uniform magnetic field exists in the plane of paper pointing from left to right as shown in figure. In the field an electron and a proton move as shown. The electron and the proton experience.Electron Proton Movement in Magnetic Field Lines

Direction of current is taken as opposite to the flow of electron or in the direction of flow of protons.

In the given figure, the proton and electron are moving in opposite direction to each other and in perpendicular to the direction of magnetic field. So, current due to both electron and proton are in same direction. Hence, the forces acting on both will be in the same direction. By Fleming's left hand rule the direction force is pointing into the plane of paper

By: santosh