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

Explanation

The negatively charged electron tends to move towards north due to the electric field.
If an equal magnetic force acts in south direction then the electron will not be deflected. Using Fleming's left hand rulle and considering the conventional direction of flow of charge from east west we get direction of magnetic field along the vertically downward direction.