Question

In a cyclotron, a charged particle
A. undergoes acceleration all the time.
B. speed up between the dees because of the electric field.
C. speed up in a dee.
D. slow down within a dee and speed up between dees.

Answer 1

Hint: We know that cyclotron is a device in which a charge particle moving along a spiral path in a constant strong magnetic field is accelerated by a rapidly varying high frequency alternating voltage. Here we applied the concept of magnetism to solve the problem of cyclotron. In the cyclotron, both the magnetic and the electric field are applied so the particle experiences a Lorentz force which is perpendicular to the direction of motion.

Complete answer:
Cyclotron accelerates the charged particles with the help of high frequency alternating voltage which is worked between two “D” shaped sheet metal electrodes known as “dees” inside a vacuum chamber. Dees are present between the two poles of a magnet which provide a static magnetic field perpendicular to the electric field formed by the applied voltage. The charged particles beam accelerated while going from one dee to another. The frequency of voltage across the both dees is set as that particle completes its one complete circuit during a single cycle of the voltage . So the frequency of cyclotron is $f = \dfrac{{qB}}{{2\pi m}}$ where $B$ is the magnetic field strength, $q$ is charge of particle and $m$ is the mass of the charged particle.

Diagram of cyclotron is shown below:

A charged particle moving in the field has an energy which depends on the magnetic field strength and the diameter of both the dees. When a charged particle is moving in the magnetic field it experiences a centripetal force which is responsible for being in the curved path.

So, the correct answer is “Option A”.

Note:
This device is not for small particles, for example electrons are very small so it can not accelerate electrons. It is not useful for acceleration of neutral particles also. So these are the limitations of cyclotron.