An electron travelling west to east enters a chamber having a uniform electrostatic field in north to south direction. Specify the direction in which a uniform magnetic field should be set up to prevent the electron from deflecting from its straight line path.

Explanation

An electron travelling west toe east on entering a chamber having uniform electrostatic field in north to south direction will be defected towards north. To prevent the electron from deflecting from its straight line path, the direction of deflection due to magnetic field must be opposite to that of electrostatic field. Thus, magnetic field `vecB` should be in a vertically downward direction so that is accordance with Fleming.s left hand rule the deflection of electron due to B is in horizontal plane from north to south and may nullify the deflection due to electrostatic field.