JJ Thomson Cathode Ray

Introduction to JJ Thomson cathode ray

JJ Thomson received the Nobel prize in 1906 for his revolutionary work on the discovery of electrons.

He discovered electrons from the minute observations while performing the cathode ray tube experiment.

He added a number of enhancements in the cathode ray tube experiment, the results of which proved that there did exist subatomic particles. Prior to the discovery of electrons by JJ Thomson, all scientists believed that atoms were the smallest units of matter and they were indivisible.I like to share this Examples of Momentum with you all through my article.


Description of JJ Thompson cathode ray tube experiment


The cathode ray tube experiment comprises of the following arrangement:-

A long glass tube called the cathode ray tube is taken and evacuated so that air pressure inside it falls to a very low value - around 10^-2 to 10^-6 Pascals.

A metal cathode and a metal anode are fixed inside the two ends of the cathode ray tube described above.

The metal anode is connected to the positive terminal of a battery and is thus also called as the positive electrode.

The metal cathode is connected to the negative terminal of the battery and is thus also called as the negative electrode.

When electric current passed through the circuit, fluorescent green rays called the cathode rays were emitted from cathode and traveled towards the anode.



Observations and conclusions of JJ Thomson from the cathode ray tube experiment


JJ Thomson observed the following points from the cathode ray tube experiment that led him to the discovery of electrons.

Observations and their corresponding conclusions

The cathode rays were attracted by the positively charged anode - thus, the cathode rays were negatively charged.

The cathode rays were deflected by electric and magnetic fields - this further proves that they were negatively charged.

The cathode rays cast shadow of an object kept in their path - this proves that they travel in straight lines.

The cathode rays cause a light paper wheel kept in their path to rotate about its axis - this proves that they are composed of particles of some kind, because only matter can cause matter to move.

These were the main observations made by JJ Thomson in his cathode ray tube experiment. Thus, he concluded that the cathode rays consisted of some negatively charged particles called electrons, and thus, an atom could not be indivisible. The discovery of electrons in the beginning of the 20th century marked the beginning of a century of further discoveries that would introduce new concepts in science.

Paramagnetism and Diamagnetism

Introduction to Paramagnetism and Diamagnetism:

1. Diamagnetic substances are those which have tendency to move from stronger to the weaker part of the extended magnetic field.  In other words, unlike the way a magnet attracts metals like iron, it would repel a diamagnetic substance.

2. Paramagnetic substances are those which get weakly magnetized when placed in an external magnetic field.  They have tendency to move from a region to weak magnetic field to strong magnetic field i.e. they get weakly attracted to a magnate.



Diamagnetism: paramagnetism and diamagnetism


Diamagnetism: The simplest explanation for diamagnetism is as follows:

(a)Electron in an atom orbiting around nucleus possess orbital angular momentum.  These orbiting electrons are equivalent to current carrying loop and thus possess orbital magnetic movement.

(b)Diamagnetic substances are those ones in which resultant magnetic movement in a atom is zero.  When magnetic field is applied those electrons having orbital magnetic movement in the same directions slow down and those in the oppo0site direction speed up.  This happens due to induced current in accordance with the lenz’s law.

(c)Some diamagnetic materials are bismuth, copper, lead, silicon, nitrogen, water and sodium chloride.

(d)Diamagnetism is present in all the substances.  However, the effect is so weak in most cases that it gets shifted by other effects like paramagnetism, ferromagnetism etc.

(e)The most exotic diamagnetic material are super conductors.  These are metals, cool to very low temperatures which exhibits both perfect conductivity and perfect diamagnetism.  A superconductor repels a magnet and is repelled by the magnet.


Paramagnetism: paramagnetism and diamagnetism


Paramagnetism:

(a)The individual atoms of a paramagnetic material posses a permanent magnetic dipole movement of their own.  On account of the ceaseless random thermal motion of the atoms, no net magnetization is seen.

(b)In the presence of external field, which is strong enough, and at low temperature, the individual atomic dipole movement can be made to align and point in the same direction as the external field.

(c)Some paramagnetic materials are aluminium, sodium, calcium, oxygen and copper chloride. Experimentally, one finds that the magnetization of a paramagnetic material is inversely proportional to the absolute temperature T.

M = CB0/T

This is known as Curie’s law.

Physical Weathering of Rocks

Introduction to Weathering:

Weathering is a process where the earth’s rocks, soil, and mineral break down due to the direct contact with the planet’s atmosphere. The weathering occurs due to no movement, this is called as ‘situ’. The man-made structures also face weathering problems due to atmospheric exposure. Weathering is of two types, physical weathering, here the breakdown of the rocks and soil is due to the atmospheric conditions such as ice, water, heat, and pressure.Another type is chemical weathering, it is a process where the earth’s rocks and soil breaks down due to the effect of the earth’s atmospheric chemical directly on them.Please express your views of this topic Internal Energy Equation by commenting on blog.


Physical Weathering:


In physical weathering abrasion is the primary process, the physical and chemical process are inter related, as the cracks created by the physical process are increased in the surface area by the chemical reactions on it.


Type in physical weathering:

Thermal stress: Thermal stress weathering is process which causes due to the expansion and contraction of the rocks as a result of temperature change. This is more common in the desert and the regions where the temperature is higher in the day time and cooler at the night.
Frost weathering: This type of weathering is common in the regions where the temperature is nearer to or around the freezing point of water. Here the soil or rocks get cracked due to the low temperatures
Pressure release: Here the materials which is not necessarily rocks having a heavy mass are removed or it is also known as unloading of overlaying materials. This is done by some erosion or other processes. As these over laying materials are heavy they create pressure on the underlying materials.
Hydraulic action: This action occurs in the rock face when the water rushes rapidly in the cracks. At the bottom of the crack the water and a layer of air gets trapped, this causes explosion when the wave retreats which results in crack widening.

5 Forms of Energy

Energy represents itself in various forms. For a physics student it is required that he must be aware of all these forms. In this article we shall discuss the 5 forms of Energy.I like to share this Heat Transfer Rate with you all through my article.

Introduction to the 5 forms of Energy
Energy is defined as the amount of work done by a force.
Energy can neither be created nor be destroyed. It can only be changed from one form to another.
Five forms of energy:
(a) Heat energy

(b) Internal energy

(c) Electrical energy

(d) Chemical energy

(e) Nuclear energy


Description of 5 forms of energy


1. Heat energy :It is the energy possessed by a body by virtue of random motion of the molecules of the body.

2. Internal energy : It is the total energy possessed by the body by virtue of particular configuration on its molecules and also their random motion.  Does internal energy of the body is the some of potential and kinetic energies of the molecules of the body.  Potential energy is due to configuration of the molecules against inter molecular forces and kinetic energy is due to random motion of the molecules.

3. Electrical energy : Electrical energy arises on account of work required to be done in moving the free charge carriers in a particular direction through a conductor.


5 forms of Energy (cont.)


4. Chemical energy : Chemical energy of a body, say a chemical compound is the energy possessed by it by virtue of chemical bonding of its atoms.  The chemical energy becomes available in a chemical reaction.  Chemical energy arises from the fact that the molecules participating in the chemical reaction have different binding energies.  A stable chemical compound has less energy then the separated parts.  A chemical reaction is basically a rearrangement of atoms.

5. Nuclear energy : Nuclear energy is the ;energy obtainable  from an atomic nuclear.  Two distinct modes of obtaining nuclear energy are :

(a)             Nuclear fission

(b)             Nuclear fusion

Nuclear fission involves splitting of a heavy nucleus into two or more lighter nuclei, where as nuclear fusion involves fusing of two or more lighter nuclei to form a heavy nucleus.

Importance of Atmosphere

Introduction to importance of atmosphere:

The envelope of the air which surrounds our earth is called “atmosphere”. In fact, we the human beings and other living organisms live at the bottom of an ocean of air. The atmosphere extends to a height of 120 Km. It is present everywhere on the earth. All living beings need air in one form or another form. Atmosphere is divided into four major layers: Troposphere, Stratosphere, Mesosphere and Thermosphere. The composition of the components of air keeps on changing on the account of following reasons:


Atmosphere is a mixture of gases of different densities among which water vapour is one of the lightest gases, followed by nitrogen, oxygen and carbon dioxide.
There is a drop in temperature and pressure with the increase of height.

Importance of Atmosphere:


Atmosphere plays an important role in the formation of clouds, occurrence of rain and formation of snow. It prevents certain harmful radiations from reaching the surface of the earth. It also helps in the formation of winds. The studies on atmosphere also help in making weather forecasts. The weather forecasts help us in taking necessary measures to prevent loss of human life, cattle and crops due to torrential rainfall, cloud brusts, cyclones and dry spells. It also facilitate in taking appropriate measures against droughts and floods. In a way, weather forecasts help us in disaster management.


Importance of Atmosphere:


The envelope of air protects all living beings from the harmful ultraviolet radiations coming from the sun. These rays can cause skin cancer and various health problems, If they reaches our earth. It plays an important role in the formation of winds. Fast moving winds are used for running windmills. The windmills are used for drawing underground water, flour mills and for generating electricity. Winds do help in the movement of sailing ships, gliders etc. Due to presence of atmosphere, transmission of sound is possible. Some musical instruments work only due to presence of atmosphere. The presence of atmosphere enables earth to maintain suitable temperature on the earth for the survival of the living beings.

Ordinary Dry Cell

Introduction to ordinary dry cell:

The best known voltaic cell for commercial use is the ordinary dry cell. The dry cell which we use in torches, transistor radios, toys and laboratory experiments, was invented by Lechlanche in 1868. The dry cell converts chemical energy into electric energy. A single dry cell gives a voltage of 1.5 volts.


Construction of ordinary dry cell


A dry cell consists of a carbon rod placed at the centre of a zinc container. The space between the carbon rod and the zinc container is filled with a moist paste of ammonium chloride (NH4Cl) and zinc chloride (ZnCl2) mixed with manganese dioxide and powdered carbon. In dry cell, the carbon rod acts as a positive electrode (cathode); the zinc container act as a negative electrode (anode); and the ammonium chloride and zinc chloride acts as electrolyte. Manganese dioxide removes the hydrogen gas formed during the working of dry cell (by oxidising it), and prevent it settling on the positive electrode of the cell (so that it may not interfere with the working of the cell).


How ordinary dry cell works:


Actually, manganese dioxide works as depolariser (depolariser is a chemical which removes hydrogen and prevent it settling on the positive elctrode of the cell). powdered Carbon present in the dry cell helps in the movement of charges between the electrodes in the cell and hence reduces the internal resistance of the cell. Please note that a dry cell is not completely dry. The presence of little water in the miost paste is essential for the movement of ions.The dry cell is sealed at the top with the sealing wax to prevent evaporation of moisture and the carbon rod has a brass cap for better electrical contact. The zinc container has an outer insulation of card board case. The card board case, however does not cover the bottom of the cell. In dry cell , the zinc container is the producer of electrons for the usable current.

Geothermal Resources

Introduction to geothermal resources:

Geothermal energy is the heat from inside the earth, a kind of domestic energy which is reliable, cost effective and environmentally friendlier than other conventional sources of energy. It is released at an average heat flux of 60 mW/m2 by conduction. It is used for direct-heat use and electrical power generation.

Through production wells hot water is pumped up from the underground reservoir for generation of electricity, and then converted to steam by discharge of pressure. The steam is led into a turbine engine, which turns a generator. Remaining geothermal fluid is goes back into the reservoir to maintain its pressure.


Resources for geothermal energy


The global tectonic plates dictate the location of geothermal resources. Geo-dynamic processes like subsidence, sub-duction, uplift, fracturing result in geothermal features like volcanism and hydrothermal convection.

Common geothermal resources are:

A deep simple hot rock or magma body.

Heat carrying fluid.

Fractured or spongy rock.

Top rocks provide an insulating cover

The general geothermal resources need a fluid for heat transfer.

For direct-heat application, heat is extracted from the geothermal water at temperatures less than 120 o C which is used for greenhouse, home heating, vegetable drying and other small scale industries. The hot water spent, is used for direct application.


Technology and Resource Type


Geothermal resources  can be just liquid water, dry, a mixture of steam and water or mainly steam and varies in temperature from 30-350 o C. Water is the medium to transfer geothermal heat from the earth which is naturally occurring in most places but modern technologies extract this energy from hot dry rock resources. The temperature of the resource indicates the type of technologies required or its uses.


Conclusion to geothermal resources


Geothermal electric plants are built on the edges of tectonic plates as high temperature geothermal resources are available close to the surface

There are approximately 8,000 MW of generating and 12,000 MW of direct use geothermal resources world-wide.