Hiii vikash

A big recommendation from my side ....

# for question (1) Refer to any well known side book for XI CBSE board....like Pradeep ..(remeber these books are good for such type of question like working and principle ....but not good for JEE) ...

#For question 2 ..refer to class 10 physics side book S.chand ....there nuclear reactor is explained very well ....

After all about the question...i am explaining it as best as i can

CYCLOTRONE

Given below is the simple layout of the cyclotrone ..

High speed charged particles are required for nuclear and atomic investigations. Cyclotron is one of the devices popularly known as “particle accelerator” to accelerate charged particle to a very high speed. It uses “crossed” magnetic and electric fields at right angles to achieve the objective. The chief role of magnetic field is to make the process of acceleration confined to a small and manageable region. As far as the change in speed is concerned, it is affected only by the electric field.

ACCELERATION

Electric force accelerates particle only to change its speed if motion of the charged particle is in the direction of electric field. A potential difference V accelerates particle to achieve a speed as given by :

1/2 mv^2 = eV  

so  v  = root(2eV/m)

Construction

It consists of two hollow semicircular Dees so named because of their D-shape. The plane of Dees is the plane of revolution of charged particle, preferably a plane midway in  the Dees. The Dees are constructed of conducting material like copper in order (i) to function as electrodes for applying alternating electrical potential using electrical source known as “electrical oscillator” and (ii) to shield moving charged particle from electric field within the Dees. The Dees are kept face to face diametrically opposite at a small distance known as the “gap”. Electric field operates only in the gap to change speed of the charged particle. We should note that electric field does not accelerate charged particle when it is moving along semicircular path within the Dees as it is shielded from electrical field.

There is an exit channel at the perimeter of one of Dees which finally guides the accelerated charged particle towards a target. The whole set up of Dees is placed between two poles of a powerful magnetic such that its field is perpendicular to the plane of Dees and hence perpendicular to the plane of motion.


This system of Dees is placed in evacuated confinement so that the charged particle moves unhindered.(refer to figure mentioned above)

Working Principle

The charged particle (say a positively charged proton) is released near mid point of the face of one of the Dees. Being in the electric field from one Dee to another, it is accelerated by the electric force in the direction of electric field. As the particle enters the adjoining Dee, the magnetic force, being perpendicular to it, renders the charged particle to move along a semicircular path within the Dee.   By the time, it emerges again in the narrow gap separating the two Dees, the electrical polarity of Dees changes so that the particle is again accelerated again with an increase in speed.

But as the speed of the particle has increased, the radius of curvature of the semicircular path increases in accordance with the formula :



  r = mv/Bq   ( where B is magnetic field , m is mass , v is velocity , q is charge )


For given charge, mass and magnetic field, the radius is proportional to the speed. Clearly, the charged particle begins to move in a larger semicircular path after every passage through the gap. By the time particle reaches the gap successively, electric polarity of Dees keeps changing ensuring that the charged particle is accelerated with an increase in speed. This process continues till the charged particle reaches the periphery and exits through the guide with high energy and bombards a given target being investigated. The description of different segments of the path of accelerated particle is given here :


1: Path is a straight line. Particle is accelerated due to electric force. Speed and kinetic energy of the particle increase.


2: Path is a semicircular curve. Particle is accelerated due to magnetic force. This acceleration is centripetal acceleration without any change in speed and kinetic energy of the particle.


3: Path is a straight line. Particle is accelerated due to electric force in the direction opposite to the direction as in case 1. Speed and kinetic energy of the particle increase by same amount as in the case 1.


4: Path is a semicircular curve of greater radius of curvature due to increased speed. Particle is accelerated due to magnetic force. This acceleration is centripetal acceleration without any change in speed and kinetic energy of the particle.


5: Path is a straight line. Particle is accelerated due to electric force in the direction opposite to the direction as in case 1. Speed and kinetic energy of the particle increase by same amount as in the case 1 or 3.



We see that the particle follows consecutive larger semicircular path due to increase in the speed at the end of semicircular journey. The resulting path of charged particle, therefore, is a spiral path – not circular.

I hope this much explanation is quite enought to explain about cyclotrone ...but please follow my recommendation for a while ..

Regards

Yagya

askiitians_expert

Hello  vikash ....

This answer is for second part ......but refer to S.chand class X book..there you will find a very simple explanation for this...

This is from an online source ....read it for an overview

A typical nuclear reactor has a few main parts. Inside the "core" where the nuclear reactions take place are the fuel rods and assemblies, the control rods, the moderator, and the coolant. Outside the core are the turbines, the heat exchanger, and part of the cooling system.

The fuel assemblies are collections of fuel rods. These rods are each about 3.5 meters (11.48 feet) long. They are each about a centimeter in diameter. These are grouped into large bundles of a couple hundred rods called fuel assemblies, which are then placed in the reactor core. Inside each fuel rod are hundreds of pellets of uranium fuel stacked end to end.

Also in the core are control rods. These rods have pellets inside that are made of very efficient neutron capturers. An example of such a material is cadmium. These control rods are connected to machines that can raise or lower them in the core. When they are fully lowered into the core, fission can not occur because they absorb free neutrons. However, when they are pulled out of the reactor, fission can start again anytime a stray neutron strikes a 235U atom, thus releasing more neutrons, and starting a chain reaction.

Another component of the reactor is the moderator. The moderator serves to slow down the high speed neutrons "flying" all around the reactor core. If a neutron is moving too fast, and thus is at a high-energy state, it passes right through the 235U nucleus. It must be slowed down to be captured by the nucleus and to induce fission. The most common moderator is water, but sometimes it can be another material.

The job of the coolant is to absorb the heat from the reaction. The most common coolant used in nuclear power plants today is water. In actuality, in many reactor designs the coolant and the moderator are one and the same. The coolant water is heated by the nuclear reactions going on inside the core. However, this heated water does not boil because it is kept at an extremely intense pressure, thus raising its boiling point above the normal 100° Celsius.

I hope you will get cleared with these two questions after reading posts

With regards

yagya

askiitians_expert