What are the positive and negative effects of green revolution on agriculture in india for?
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Answer:
This is not possible to do with a steady (with time) magnetic field.
Simply because the Lorentz force on the electron due to the magnetic field is always perpendicular to it, hence it will never be able to act along the negative x-axis.
However, there is a clever way that one can effectively reverse its direction without invoking an electric field:
Let the magnetic field be set up such that its direction is perpendicular to the direction of motion of the electron, along the yy or zz axes. As the electron enters the region of the magnetic field, it starts to go around it, all the time its motion staying in the same plane as it entered. Now, imagine switching off the magnetic field at the moment it has travelled exactly a half of its orbit, i.e. the moment its direction has reversed. As that it is done, an instantaneous electric field will be generated according to Faraday’s Law, and it will act on the electron for a very short time. Provided the magnitude can be kept small, the electron will come out with its direction reversed.