Question

why in cathode ray discharge tube of j.j thomson experiment electrons deviate to point a when only electric field is applied and strikes point c when only magnetic field is applied

Answer 1

J.J. Thomson discovered that the electrons are negatively charged particles by its experiment of cathode ray tube. When electric field was applied, the electrons, emitted from electron gun, moves to the positive side of electric field because electrons are negatively charged particles. But when magnetic field was applied there was no deflection in the path of electrons.