A particle enters a magnetic field at right angles as shown.
The direction of force acting on the particle is into the page. The charged particle is a/an:
→F=q(→v×→B)
^−k=q(^−j×^i)
^−k=q(^k)
From above eq. we can say that charge must be negative in nature.
The above charged particle experiences force into the page. Using Fleming’s left hand rule and for the above condition to be valid the direction of current must be opposite to its direction of motion. So, the charged particle must be an electron.