CBSE Class 12-science Answered

Principle:

(i) A positively charged ion can be accelerated to a high energy with the help of smaller values of oscillating electric field by making it to cross the same electric field time and again.

(ii) A charged ion moving perpendicular to a magnetic field describes a circular path.  

Construction of a cyclotron:

As shown in the labeled diagram, D₁ and D₂ are two semi—circular disc like metal containers called dees. The straight sections of the dees are open so that the ions can move freely from D₁ to D₂ and vice—versa. A high frequency oscillating electric field is applied to the dees. The whole assembly is enclosed in an evacuated steel box to avoid collisions between the ions and the air molecules. A source of ions, to be accelerated, is placed at O between the two dees. A strong magnetic field is applied in a direction perpendicular to that of oscillating electric field, by using two pole pieces of strong electromagnets N, S.