Magnetic Field Due To A Current Element Biot Savart Law

A solenoid produces a magnetic field that is similar to the magnetic field produced by a bar magnet. The magnetic field inside a solenoid is uniform and resembles the field inside a bar magnet, with distinct north and south poles. A bar magnet also generates a similar magnetic field with similar characteristics, such as a dipole field. Therefore, a solenoid and a bar magnet can produce similar magnetic fields.

The correct option is (A) : a solenoid and a bar magnet

The radius of the circular path in a magnetic field is given by the equation: where: = mass of the particle,
= velocity of the particle,
= charge of the particle,
= magnetic field strength. For an particle (helium nucleus), which contains two protons and two neutrons: (where is the mass of a proton),
(where is the elementary charge).
For a proton: and .
Given that the paths have the same radius:
Simplifying the equation, we find:
Thus, the ratio of their velocities is: Therefore, the ratio of the velocity of the particle to the proton is 1:2.