Question

A positively charged particle moving due east enters a region of uniform magnetic field directed vertically upwards. The particle will

• A. get deflected in a vertically upward direction
• B. get deflected in the opposite direction
• C. move in a circular path with anti-clockwise direction
• D. move in a circular path with clockwise direction

Answer 1

The correct option is D

move in a circular path with clockwise direction

Using Fleming's Left-Hand Rule we can point the direction of the magnetic field as coming out of the paper (Shown as dots).

The positive charge is entering the field and is moving perpendicular to the field. Here
- Index finger $\Rightarrow$ point upwards vertically in the direction of the field,
- Middle finger $\Rightarrow$ points in the direction of the current (in the direction of charge, since the charge is positive)
- Thumb $\Rightarrow$ gives us the direction of the force which will be downward here.

This propels the charge to move in the direction of the force.
But we observe that the Left-Hand Rule can be applied again in its new position- B and then we observe the particle moves
towards C.
Basically, the particle in the field continues this path which is a circular path and in a clockwise direction until the field is present.