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CYCLOTRON Class 12 Moving Charge and Magnetism 7 in HINDI
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In this Physics video in Hindi for class 12 we explained the construction and the working principle of Cyclotron. We discussed on its model and derived all the equations, like equation for the kinetic energy of the charged particle getting out of the cyclotron. We also talked about its uses and operation. • Class 12 - Moving Charge and Magnetism - Part 7 • Circular and Helical Motion in Magnetic Field - by EduPoint • • Circular and Helical Motion in Magnet... • Lecture on Cyclotron by Walter Lewin • • 8.02x - Lect 13 - Moving charges in B... • Cyclotron is used to produce high speed beam of charged particle. • Principle - It is based on the principle that an ion can acquire a large amount of energy by crossing an electric field several times. • Suppose a charge q passes a potential difference V. The energy acquired by it, • U' = q V • If that charge passes the same potential difference n times, the energy acquired by it, • U = n U' • or, U = n q V • If n is very large, despite q and V are small, we can have large energy U. • It consists of two hollow semicircular metal chambers D_1 and D_2, called dees. The two dees are placed horizontally with a small gap separating them. The dees are connected to a high frequency alternating electric field. The dees are enclosed in a small box containing a gas at very low pressure (〖10〗^(-3) mm of mercury). The whole apparatus is placed between the two poles of a strong electromagnet. • The positive ions are produced in the gap between two dees by ionization of the gas. • Theory - Let us consider that a positive ion is produced at the centre of the gap, when D_1 is at positive potential and D_2 is at negative potential. The ion moves from D_1 to D_2 due to electrostatic force. As the magnetic field inside D_2 is always normal to the motion of the ion, the ion experiences a force towards the centre of the dees following Fleming’s left hand rule and hence the ion moves in a circular motion. If B ⃗ is the magnetic field, m, v ⃗ and q are respectively the mass, velocity and charge of the positive ion and r is the radius of the circular path of the ion, then • q v B = (m v^2)/r • or, r = (m v)/(q B ) ………………………(1) • After moving along a semicircular path in D_2, the ion reaches the gap between two dees. At that time the polarity of two dees is reversed due to the alternating nature of the electric field. Now, D_1 becomes negative and D_1 becomes positive. The positive ion is now experiences an electrostatic force towards D_1 and its speed increases. The ion, now, traverses a semicircular path inside D_1. • • This process is repeated several times as the frequency of the alternating field is matched with the frequency of the circular motion of the ion. • As the ion is allowed to pass the electric field several times, its speed is increased a lot and hence a high speed ion is produced by cyclotron.
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