Question

A charged particle moves in a clockwise direction in a magnetic field which is perpendicular to plane of paper directed downwards. What is the nature of charged particle?

Answer 1

In the presence of magnetic field; the force on a charged particle is given as:
$F=q\times v\times B$
Where $q$ is the charge of the particle
$v$ is the velocity of the particle
$B$ is the magnetic field.
According to question the direction of charged particle is clock wise and, the magnetic field is inwards ( perpendicular to the plane of paper in downwards direction).See the image attached.
Apply Fleming's left hand rule, according to the rule if you point your thumb, fore finger and central finger of left hand perpendicular to each other then
The thumb represents the force acting on direction of motion.
The fore finger represents the direction of magnetic field.
The central finger represents the direction of current i.e propagation of charges.

Now consider any point on the circle, let the upper most point of circle (see image) point your thumb and forefinger in the direction of force and magnetic field respectively. you can see your central finger point in the direction opposite to the velocity of particles here. It means current flowing opposite to the direction of particles andIt is known to us that direction of current considered to be opposite to direction of electrons.

Therefore, hence the charge is negative i.e. the particle is an electron.