Question

A particle is moving towards east enters in a magnetic field directed towards north and deflected in vertically downward direction. The charge particle is 
1. an electron    2. a proton   3. an alpha particle     4. a neutron

Answer 1

We will use right hand thumb rule
As per the question, the charge is deflected in the downward direction. So, the current is in the west direction.
so its an electron

Answer 2

The charged particle is an electron. (option 1)

• The charged particle is an electron due to Fleming's left-hand rule.
• It states that " when a current-carrying conductor is placed in a magnetic field, there is a force exerted on the conductor perpendicyularly and in the direction of the flow of current".
• Electrons are the particles that are responsible for the flow of current in a conductor.
• There is actually a flow of electrons in the conductor which produces current. Without electrons there is no conduction and it does not satisfy fleming's left-hand rule too. Therefore, the answer is electrons.