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Machines and Devices

Large Hadron Collider Large Hadron Collider [LHC, CERN] – The God Particle Detector. The discovery of the God's particle namely the Higgs boson, was haunted for nearly 50 years by Physicists. Finally the Large Hadon Collider recently proved the existence of the God's particle. This particle creates a field known as Higgs field (a field of energy) which pervades all over the universe. If the elementary particles interact with this field their mass will be generated. That's how the universe was created after the Big bang. The LHC is made of huge electromagnetic devices. Let's learn more of such devices in detail, as we go through this topic.

Learning objectives

After completing the topic, the student will be able to:

  • Observe and explore the working of a Cyclotron and determine the Lorentz force acting on the moving charged particle.
  • Distinguish between the working of magnetic hydrodynamic generator and tesla generator. Also investigate the advantages in both cases.
  • Discuss and probe the working of a speaker and microphone. Also distinguish between them based on their working.
  • Examine the principle on which the generator works and investigate the differences between the types of generators.
  • Analyze the importance of transformers in daily life and investigate its types based on their applications.
Magnetic Interaction with Moving Charge Magnetic interaction with moving charge A moving charge produces magnetic field which will be effected by the external magnetic field. Hence the charge would deviate from its original direction.

The magnetic effect of electric current has many applications. For example, electric motors, transformers, telephone receivers, microphones, loudspeakers, measuring instruments like galvanometer, voltmeter, ammeter etc., are based on this effect. Thanks to the discoveries of Faraday, Lenz, Tesla and others, we are able to use their principles for generating electricity, run electric motors and in general enjoy all the advances of modern science and technology.

We will now see how all the laws and principles discussed in Electromagnetism are made use of in a few important electrical machines and devices. The interaction of a moving charge (or current) with a constant magnetic field can be visualized as follows:

When a charge q moves at a velocity v through an electric field E and a magnetic field B, total Lorentz force is given as

Cyclotron Diagram of Cyclotron operation A Cyclotron is a type of particle acceleration in which charged particles accelerate outwards from the center along a spiral path. The particles are held to a spiral trajectory by a static magnetic field and accelerated by a rapidly varying electric field. Cyclotrons were the best source of high–energy beams for nuclear physics experiments. The results enable the calculation of various properties, such as the mean spacing between atoms and the creation of various collision products.

One of the interesting applications of this is in particle accelerators such as a cyclotron. In a cyclotron, magnetic field is applied in a direction perpendicular to the velocity of the charged particle and the electric field is applied parallel to the motion of the charged particles. Thus, the magnetic field is used for bending the beam and the electric field is used for accelerating the beam.

A cyclotron consists of a pair of semicircular hollow metal chambers. These chambers are called "dees" because of their resemblance to the English letter D. The two dees are kept close to each other with a gap between them to form a circular chamber. The entire assembly is kept between the pole pieces of two magnets so that there is uniform magnetic field inside the chamber. The two dees are connected to terminals of an alternating voltage source. The frequency of the alternating source matches with the velocity of the charged particles.

Each time the charged particle q gets an additional energy qV, due to electric potential difference V, the radius of its orbit becomes larger and larger. When the energy of the charged particle reaches a required value, they are removed from the dees using deflector plates.

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