Question

A proton is moving along the Z-axis in a magnetic field. The magnetic field is along the X axis. The proton will experience a force along
A. X-axis
B. Y-axis
C. Z-axis
D. Negative Z-axis

Answer 1

Hint: The force experienced by a point charge due to an electric and magnetic force due to electromagnetic forces is given by Lorentz force. It is also known as electromagnetic force.


Formula used:
The magnetic force is proportional to electric charge ‘q’ of the particle and to the magnitude of vector cross product of velocity ‘v’ and the magnetic field ‘B’.
Mathematically it is written as
\[F = q(\overrightarrow v \times \overrightarrow B )\]

Complete answer:
When a charged particle moves in a magnetic field it experiences a force. Given that the velocity of the proton is along Z-axis and magnetic field is along X-axis, therefore, the direction of force on a charged particle will be given by
\[F = \widehat v \times \widehat B\]
\[F = ( + \widehat k) \times ( + \widehat i)\]
\[F = + \widehat j\]
That means the moving proton will experience a force along the Y-axis.
Hence, Option B is the correct answer.




Note: The direction of Lorentz force acting on the charged particle is perpendicular to the magnetic field and the charge moving which can easily be explained by Lorentz Force Right Hand Rule. If the electric field, magnetic field and direction of velocity are parallel, the charge is moving in rectilinear motion. But if the direction of velocity is perpendicular to electric and magnetic fields and both fields are parallel to each other, then the charge will be moving due to the electric field and hence move in a circular motion.