An eletron beam is deflected in a given field. How will you detect whether the given field is a uniform magnetic field or a uniform electric field?

Explanation

We can detect the nature of field by observing the trajectory and measuring the kinetic energy of electron. In a uniform electric field, the path of electron beam moving perpendicular to field will be a parabola and the kinetic energy (and hence the speed) of the electron changes. In a uniform magnetic field, the path of electron beam perpendicular to field will be circular and kinetic energy (and hence the speed) of the electron does not change.