Question

A homogeneous electric field E and a uniform magnetic field B pointing in the same direction. A proton is projected with its velocity parallel to E, It will
A . go on moving in the same direction with increasing velocity
B . go on moving in the same direction with constant velocity
C . turn to its right
D . turn to its left

Answer 1

Hint:In this question we have to use the concept of force experienced by a charged particle moving with a certain velocity in an electric field as well as magnetic field. A magnetic force acts on a charged particle when it moves in a magnetic field, causing it to deflect. The charge, speed, and magnetic field strength of the particle all affect how strong the magnetic force is. The electric force depends on the charge and the electric field in the same way that it does for an electric field.






Formula used:
The magnetic force:
F=qvB; here, q denotes the charge, v the particle's speed, and B the magnetic field.
The electric force is given by,
F=qE; here, q denotes the charge, and E the electric field



Complete answer:
Magnetic Force is given by,
F=q(v×B)
Now, E(electric field) and B(magnetic field) have the same direction. Also, v has the same direction as E. So, the cross product of velocity and magnetic field (v×B) =0. Therefore, the magnetic force is equal to 0 on the proton. But the velocity increases due to electric force (F=qE).
An electric field exerts a force on a charged particle that is parallel to the electric field vector for positive charges and anti-parallel for negative charges. It is independent of the particle's speed.
The correct answer is A.



Note:A force is applied to a particle when the magnetic field and particle are moving perpendicular to one another. If the magnetic field and the particle are moving in the same direction, there is no force exerting on the particle.