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

  1. forces both pointing into the plane of paper
  2. forces both pointing out of the plane of paper
  3. forces pointing into the plane of paper and out of the plane of paper, respectively
  4. force pointing opposite and along the direction of the uniform magnetic field respectively


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.

The correct option is A.

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