SATELLITES

The objects moving around a planet are called the satellites of that planet. The moon moves around the earth hence moon is a satellite of the earth. The moon is a natural satellite of the earth. The centripetal force must be provided for moon to move around the earth . Here the necessary centripetal force is provided by the gravitational force between the moon and the earth.
In the same way by providing necessary centripetal force by by the gravitational force between the earth and the object it is possible to make it to move around the earth . These days there are very large numbers of human beings made satellites i.e. artificial satellite moving around the earth in different orbit saving different purpose,such as transmission of tv and radio programs for the telecommunication purposes etc.
LAUNCHING SATELLITE'S:
When satellite are made to move away from the earth's gravitational field the minimum velocity required is 11.3k/s or 40320 km/hr. Using a single stage rocket it is not possible to have so much velocity. Hence for launching satellites multistage rockets are used. Generally for such purposes 3-stage rockets satellites is always kept at the rckets are used.
In the rockets satellites is always kept at the top of the third stage . During launching of the rockets the burnt fuels comes out from the nozzle of the rocket, Then according to the third law of motion the opposite reaction that exceeds rockets weight lift and moves the rocket in upward direction. The rocket accelerates upwards and rises vertically upward so that it passes through the denser atmosphere with least time. Then first stage of the second stage makes the rocket to move with high velocity. After moving through certain distance attaining the height speed the second stage of the rocket also detached and falls back. Using the final third stage of the rocket the satellites is turned in the horizontal direction and is given proper speed for the satellite so that it remains on the orbit.Then the satellite moves around the earth in a closed orbit.

PHOTOMETRY

Light is a physicaal quantoty. Hence as other physical quantity light is also must be measurable. The branch of light that deals with the measurement of light called photometry. In photometry, we have to know about some definitions as given below.
LUMINOUS ENERGY: Light is a measurable physical quantity. Just as electric current flows through a conducting wire the light is also the flow of flux or radiant energy called the luminous energy.Light can be taken as aform of energy since light can be converted to other forns of energy and similarly other forms of energy can also be converted to light for examples:

1. PHOTOCEL:It converts light to electrical energy.
2. SOLAR BATTERY:It converts light to electrical energy.
3. BULBS:It changes electrical energy to light energy and heat .

Hence according to the principle of conservation of energy, light must be a form of energy.

Terrestrial Magnetism: Exploring Earth's Magnetic Field and Its Significance

Introduction:
In early times people thought that the north started attracting the north pole of the magnetic compass. But later a physician William Gilbert interested in scientific experiments suggested that the earth itself behaves like a huge magnet. For verification, he made a clay sphere and kept a long lode of some magnets inside the sphere with two poles one at the top and the other at the bottom. Then he made a dipping needle compass that could dip and down only and held it near one person of the lodestone. He found that the needle pointed towards the center of the sphere. When he held the dipping needle at the center of the sphere the needle set parallel to the horizontal. When he held the dipping needle near the equator of the lodestone, the needle was itself parallel to the line through the two poles. Gilbert concluded that the earth is a magnet dipping needle that should till down More and more as the needle is carried north and that it should point straight down at the magnetic equator, the dip of the needle is zero. Thus the two poles at which the needle shows 90 degrees are known as the poles of the Earth. They are not at the same points as the geographical poles. The angle between the two lines joining the two magnetic poles and the other joining the two geographical axes makes about 17 degrees. The line joining the points where the angle of inclination is zero is called the magnetic equator.

Characteristics of Earth's Magnetic Field:

Magnetic Dipole: Earth's magnetic field can be approximated as a magnetic dipole, with a north magnetic pole near the geographic South Pole and a south magnetic pole near the geographic North Pole. This results in a magnetic axis that is tilted concerning the rotational axis of the Earth.

Magnetic Declination: Magnetic declination is the angle between true north and magnetic north. It varies based on geographic location and changes over time due to the movement of Earth's magnetic field. Accurate knowledge of magnetic declination is essential for navigation and compass use.

Magnetic Intensity: Magnetic intensity refers to the strength of Earth's magnetic field at a specific location. It is commonly measured in units of tesla (T) or its subunit, nanotesla (nT).

Magnetic Anomalies: Earth's magnetic field exhibits variations known as magnetic anomalies. These anomalies can occur due to variations in the composition and magnetization of rocks beneath the Earth's surface. Studying these anomalies provides insights into geological structures, mineral exploration, and plate tectonics.

Measurement Techniques:

Scientists employ various methods to measure and study Earth's magnetic field:

Magnetometers: Magnetometers are instruments used to measure the strength and direction of magnetic fields. They range from simple handheld compasses to sophisticated devices like fluxgate magnetometers and proton magnetometers, capable of providing detailed magnetic field data.

Magnetic Observatories: Permanent magnetic observatories are established at various locations worldwide to monitor and record Earth's magnetic field over time. These observatories contribute to global magnetic surveys and aid in detecting long-term changes and magnetic disturbances.

Satellite Missions: Space-based missions, such as the European Space Agency's Swarm mission, utilize satellite magnetometers to gather high-precision magnetic field measurements. These missions enable the mapping of Earth's magnetic field on a global scale, providing valuable data for scientific research.

Significance and Applications:

Terrestrial magnetism holds immense significance across scientific disciplines and practical applications:

Geophysics and Earth Science: Studying terrestrial magnetism helps us understand Earth's internal structure, including the composition of the core, mantle, and lithosphere. It provides insights into the dynamics of the Earth's interior, plate tectonics, and the history of the planet.

Navigation and Compass Use: Earth's magnetic field has long been utilized for navigation. Compasses rely on the magnetic field to indicate a direction, allowing mariners, aviators, and hikers to navigate accurately.

Magnetic Field Protection: Understanding the behavior of Earth's magnetic field is crucial for protecting sensitive electronic devices, power grids, and communication systems from the effects of geomagnetic storms and solar flares.

Archaeology and Paleomagnetism: The study of ancient magnetic fields preserved in rocks, sediments, and archaeological artifacts, known as paleomagnetism, helps in reconstructing Earth's past magnetic field. This field provides valuable insights into geological time scales, past continental drift, and the movement of tectonic plates.

Space Weather and Ionospheric Studies: Terrestrial magnetism plays a significant role in space weather research. Variations in Earth's magnetic field interact with charged particles from the Sun, resulting in phenomena such as auroras and geomagnetic storms. Understanding these interactions is crucial for satellite operations, space missions, and radio communications.

Environmental Monitoring: Changes in Earth's magnetic field can be indicative of environmental factors such as underground water flows, volcanic activity, and seismic events. Monitoring magnetic field variations assists in detecting and assessing these environmental changes.

Magnetic Resonance Imaging (MRI): Medical imaging techniques like MRI rely on the principles of magnetic fields and their interaction with atoms in the human body. Terrestrial magnetism provides a foundation for understanding the behavior of magnetic fields in these medical applications.

Conclusion:

Terrestrial magnetism, the study of Earth's magnetic field, is a fascinating field of research with diverse applications. From its origin in the Earth's core to its effects on navigation, geophysics, and space weather, understanding the properties and characteristics of Earth's magnetic field provides valuable insights into our planet's past, present, and future. Through the use of sophisticated measurement techniques and ongoing scientific investigations, we continue to unravel the mysteries of terrestrial magnetism and its profound influence on our lives.

DEPTH KNOWLEDGE MECHANICS

AXIAL VECTOR:
Those vectors related with rotation or responsible for rotation.Example angular momentum,angular velocity etc.
POLAR VECTOR:
Those vector related with translation or responsible for translation .Example force,displacement,velocity etc.

• A vector must be changed if we change its magnitude ,direction or both .
• A vector is not changed if it is slide parallel and due to change of co-ordinate x-axis.

Q} A vector is not changed if
ans: slides parellely.
ADDITION OF TWO VECTORS:

• Resultant of any two vectors lies along major diagonal when the angle between both vector less than 90 degree.
• Resultant lies along minor diagonal when the Angle between both vector is obtuse.
• Minimum number of unequal vectors lying on same plane required to make R=0 is 3.
• Minimum number of unequal vectors not lying on same plane required to make R=0 is 4.
  

CONCEPT IN SOUND

1. WAVE AND SOUND

WAVE:Way is a disturbance,which can be transfer from one place to another place to the another place due to repeated periodic motion of the particles of the medium about their mean position.
LONGITUDINAL WAVE +TRANSVERSE WAVE=ripple wave

• Wave produced in a string=1 dimensional
• Wave produced in water=2 dimensional
• Sound and light wave=3dimensional

Wave are two types :

1. Mechanical wave
   
2. Non mechanical wave

• For the propagation mechanical wave, elasticity as well as density of medium is required that's why mechanical wave is also known as elastic wave.

• In a non -mechanical wave,vibration takes place in both electric field as in magnetic field that's why non-mechanical wave is also known as electromagnetic wave.

• Medium is required for the propagation of mechanical wave. For example wave produce in a string ,spring,sonometer wire, tuning fork and sound wave etc.
• There is no requirement of medium for the propagation of non-mechanical wave.Example:light,X-rays, Gama rays, radiation and radio waves.

1. MECHANICAL WAVE:

Mechanical wave are two types:

• Transverse wave
  
• Longitudinal wave

If wave is longitudinal,it must be a mechanical wave and if wave is mechanical then

• It may be longitudinal wave.
• It may be transverse wave.
• It may or may not be longitudinal.
• It may or may not be transverse.

1. NON-MECHANICAL WAVE:

All non -mechanical waves are only transverse in nature
If wave is non-mechanical then must be a transverse wave and wave is non-mechanical wave then

• It may be mechanical wave .
• It may be non-mechanical wave.
• It may or may not be mechanical wave.
• It may or may not be non-mechanical waves.
  

DEPTH KWOWLEDGE IN ELECTROSTATICS

COLUMBUS LAW:

• Two charges express Columbus force due to interaction electric lines of force produce by charges.
• Magnitude of Coulomb;s force on the two charges will be always equal and opposite direction even charges and their masses may be or may not be equal and charges may be like or unlike.
• Force with negative sign represent attractive force and the convention is applied only in magnitude form.
• Above convention is applied only for Coulomb force, gravitational force and magnitude force between two current carrying wire.
• An electron is accelerating with potential of 1volt. Then find kinetic energy and speed gained by electron. Electron, proton,deuteron,Triton accelerating with potential of 1volt kinetic energy gained=1Ev=1.6^-19J.
• Insulator and conductor commonly called as dielectric is used as between charges to very Coulomb force and other electrostatics quantities.
• For pure water K=81(maximum) where K is relative permittivity or dielectric constant.
• For perfect insulator k=o i.e. perfect insulator cannot be charged by any method.
• Dielectric constant of medium epsilon cannot be equal to 1.
• Coulomb force will be maximum if between the charges is air or vacuum and after putting single dielectric completely between the charges then force, decrees by k time.
• If a conductor is kept completely or partially between the charges than Coulomb force decreases to zero.Since electric lines of force produced by charge cannot interact.
• Conductor constant is defined as property of medium which oppose electric lines of force.
• Conversation of charges is consequence of principle of continuity.
• Another left things i will write in another article.
  

Electric potential

If a small positive test charge is placed at a point in an electric filed due to a positive source charge moves away from the source charge. Similarly, if the positive test charge is placed at a point in an electric field due to negative source source charge, the test charge is is found to move towards the source charge. These statements suggest that every point in an electric field have potential. The potential of a point in an electric field is called electric potential.
The electric potential is analogous to the gravitational potential .The electric potentials at different points in the electric field may be different.When a mass moves from one to another point, the gravitational potential energy of the gravitational field is converted into the kinetic energy of the mass. Similar is the case in case of charge moving in an electric Field. When a charge moves in an electric field., the potential energy of the two points in the electric field is converted into the kinetic energy of the charge. Similarly, if a charge is to move against an electric field, the kinetic energy of the charge is converted into the electric potential energy. The electric potential at a point in an electric field is defined as the amount of work done in bringing a unit positive charge from infinity to that point.

Brief introduction to optics

Light is a from of energy stimulates the sensation of vision and makes us see objects around us. Light is emitted by bodies which are heated to very high temperature,such as glowing electric bulb,burning candles,sun,etc.Light can travel through vacuum, It does not require material medium to travel from one place to other.
When light falls on an object,it is party reflected. We see the objects only when the light reflected from the objects enters into our eyes. Regarding the nature of light,Newton put forward the corpuscular theory of light. According to this theory, light consists of tiny elastic particles called corpuscles. A light source emits such corpuscles in all directions when these cor pules strikes an objects, they are partly reflected and the reflected corpuscles enter into our eyes and we see the objects. On the basis of this theory, phenomena like rectilinear propagation,reflection and refraction of light can be explained. At about the same time Huygens proposed wave theory of light. According to this theory, light is propagated in the form of wave through either which was assumed to be present everywhere.This theory explain besides reflection, refraction of light other phenomena like interference,diffraction and polarisation of light. But because of newton's popularity at that time, his corpuscular theory prevailed, and the wave theory remained in the black ground for over a century.
Later, experiments on the measurements of the velocity of light in different media showed that the velocity of light in denser medium, like water or glass, is smaller than the velocity of light in air. According to Newton's corpuscular theory, the velocity of light in denser medium should be greater than that in rarer medium with these experimental results, wave theory of light become general acceptance from scientific communities.
Still latter, it was found that when light of suitable frequency is incident on certain metals, electrons are emitted. This phenomenon could be explained only by assuming that light is absorbed or emitted in the form of quantum of energy .Each quantum of energy is a packet of energy called photon .Photons behave as particles.

Electric Measurement

Basically, electric measurement means measurement of current, voltage and resistance in a circuit.We have already discussed that a voltmeter is used for measuring current. Both of these instruments work on ohm's law. The fundamental law in current electricity. Certainly, we did not discuss about the measurement of resistance. The instrument to the a resistance is called ohmmeter. An ohmmeter ,in fact, is a combination of a voltmeter and ammeter. It is important to note that all of these electrical instruments use energy from the source of electricity of which they are doing the measurement. It is, therefore, there fore, the measurements taken by them are slightly different from the actual measurements . In other words, some accuracy of measurement is lost with these instrument.
Hence , if we need move accuracy in the electrical measurement,we use potentiometer and Wheatstone bridge for the measurement of electricity. These devices use elaborate circuits for the measurement. However, these devices are much more accurate them the other.
In this sub-unit,we discuss in detail the principle and applications of accurate electrical devices.

Transfer of heat

Heat is a form of energy. Heat energy can be transfered from one place to another. Now , we talk about the mechaniisms of transfer of heat by conduction method. Conduction is one of the mechanisms of heat transfer. This takes place usually in solids. When ther exists temperature difference betwwen two points in solid, transfer of heat akes place from the point at high temperature to the point at low temperature without transferring the mass. This kind of transfer heat without transfer of mass is called heat conduction.

Heat conduction in solids can be explained the basis of kinetic theory of matter.A solid is made of a number of atoms which are fixed at lattice sites and are capable of vibrating about their mean positions.the amplitude of vibration of yhese atoms increases with the increase of temperature of solid.

Suppose that one end of a solid of bar is heated. The temperature if that end increases and the atoms in that region to vibrate with higher amplitudes due ro gain of thermal of heat energy. As a result, they collide with neighbouring atoms in cooler region . During such collision hot atoms transfer thermal energy to tje cold atoms and these atom also will begin to vibrate with higher amplitude. In turn, these neighbouring atoms collide with nextneighbouring vold atoms and so on. Thus, there will be continous transfer of heat thermal of thermal energy towards cold end. Here,heat is transfered from one atom to the other while each atom remaons vibrating about their original positions.

In matals there are many free electrons. The electrions are very small and can travel rapidly. When a bmetal is heated,their vibration increase and the energy is passed on to pther atoms and also the numerous electrons in the metal. The electrons rapidly transfer energy by collision to other electrons and other atoms. Hence the transfer of energy n metals is rapid.In non-metallic solids,there are very few free electrions.Here the only way that hewat can transfer through the solids is by direct transfer of energy from one atom another.Hence,yhe the transfer process slow.

Effects of refraction of light

Due to refraction of light, various effect are observed in our daily life. We have many advantages by the refraction of light. The following are some example of them:

1. A clear pool of water always appears to be shallower   than  it actually is.

2. A coin placed at the bottom of beaker containing water       seems it be raised.

3. A stick partially dipped in water seems to be sent.

4. The sun appears flattened at the time of sun set and sun rise.

5. The density of the air in the atmosphere is greater near the surface of the earth than above it. 

Thus, the magnitude of refraction increases with decreasing height. Due to this, the lower portions of the sun at the time of sun set and sun rise are raised more than the upper portions. Hence, the vertical diameter of the sun is shortened more than the horizontal diameter. As a result, the sun seems flattened.

The stars seem twinkling of light. The density of the layers of the atmosphere changes continuously. Due to the changes in the density of air, the magnitude of refraction of the light rays from the stars also changes continuously. This changes causes the apparent positions of the images of the stars to change continuously with time. Hence, the stars appear to twinkle.

Earth's Satellites

A heavenly body that revolves round the earth in a circular orbit is called earth's satellite. For example, the moon is the earth's satellite which revolves round the earth in circular orbit of radius 3.84^5km. The moon takes about 27.3 days to move once round the earth.The earth's satellites are of two types: Natural satellite and Artificial satellite.

• Natural satellites:It is a naturally formed body moving around the earth.The moon is the only natural satellite of the earth.
• Artificial satellite:It is a man made body moving around the earth in an orbit.When a body is taken to a certain height above the earth and given necessary centripetal force,the body keeps on moving around the earth and becomes an artificial satellite.

Now a days, the artificial satellites find widespread application in the present world. The following are the uses of artificial satellite.

1. Artificial satellites are widely used in telecommunication.
2. They are used in studying the atmosphere near the earth surfaces.
3. They are used to forecast weather.
4. They are used to transmit radio and video signals.
5. They are used to know the shape and size of earth.
6. They are used in space flights.
7. They are used to study the radiations conform the sun and the outer space.
8. They are used to find another natural satellites which lies in our universe.
   

METHODS OF CHARGING A BODY

Making a body to acquire property of attracting small objects is called charging(or electrification). A body can by charged by the following ways:

By rubbing: When a body is rubbed with another body, both of them charged. One of the bodies acquires positive charge and the other acquires negative charge. For example, when a glass rod is rubbed with a silk, the glass rod acquires positive charges, and at the same time, the silk, the silk acquires negative charges.

By conduction: When an uncharged body is made in contact with a charged body flow into the non charged body and the body is charged. For example ,if an uncharged sphere A is made in contact with a charged sphere B, the sphere A will be charged sphere B, the sphere A will be charged with the same charge as in the sphere B.

    Figure 2: Charging by conduction

By induction: When a charged particles or body is brought near non charged body without touching, charges are developed in the uncharged body. This method of charging a body is called charging by induction. 

                                                          Figure3 : Charging by Induction

Prevot's Theory of Heat Exchange

According to prevot's theory of heat exchange a body not only radiates heat radiations continuously at all temperature but also absorbs heat continuously from the surroundings. The heat radiates by the body per unit area per unit time does not depend upon the temperature of the surroundings but only on the temperature of the body.However,the heat radiations received by the body from its surroundings.If the body radiates more heat to the surroundings then it receives from the surrounding, the body has a net loss of heat. As a result,the body will have cooling effect. Similarly, if the body radiates less heat to the surroundings than it receives from the surroundings,the body has a net gain in heat energy. As a result,the body has heating effect.If the heat radiated by the body to the surroundings is equal to the heat received by the body from the body to the surroundings is equal to the heat received by the body from the surroundings ,the body will be in thermal equilibrium with its surroundings.
therefore,if there are a large number of bodies at the save temperature, the bodies are in dynamic thermal equilibrium. A body stops radiating energy only at absolute zero of temperature.
This is called theory of heat exchange. This theory can be used to explain why we feel cold in winter and hot in summer if we come outside home.
In the winter, the surroundings temperature is less that our body. As a result, the heat energy we radiate into the surroundings is more than the heat energy we receive from the surroundings .As a result,there is net of energy for us we feel cold. However, in summer,the surroundings temperature is more than that of our body. Therefore,the heat energy we radiate into the surroundings is less than that we receive from the surroundings. As a result, there is net gain in heat energy for us and feel hot.

Evaporation and Boiling

The molecules in a liquid are at random motion. In the random motion, the different molecules have different velocities and hence different kinetic energies. In addition, the molecules of the liquid collide with each other. They may exchange their kinetic energies in the collisions. In the collisions, some of the liquid molecules may get energy enough to be converted into vapour even at low temperature.The conversion of some of the liquid molecules into even blow the boiling point is called evaporation. When evaporation takes place, the molecules which fly off the body of the liquid take the required energy for the evaporation from the remaining molecules of the liquid. Since the kinetic energy of the remaining molecules has been decreased,there is net fall in temperature of the liquid. Thus,cooling is resulted from the evaporation of a liquid.
The evaporation of liquid can be defined as slow and silent conversion of the liquid from its liquid state to gaseous state at all temperature.
It has been found that the rate of evaporation of a liquids depends upon the following:

• Nature of the liquid .
• Temperature of liquid.
• Area of the surface of the liquid.
• Pressure and temperature of the atmosphere.
• Effect of liquid.
• Humidity of the atmosphere.

However, the boiling (also called equilibrium) is a rapid and noisy conversion of a liquid into vapour at a particular temperature called boiling point.The temperature of the liquid does not change during boiling. No cooling effect is observed.

Gravity and Gravitional

Newton, in 1687, discovered the existence of a force between two masses.For example,two people sitting in a room, a table and a rock lying in a room, the sun and the earth, the earth ans the moon and so on exert force on each other.The force between two masses is called gravitational force. The gravitational force is always attractive. That is each body (or mass) attracts towards if the other body (or mass).This force exists universally among all bodies in the universe.
In gravitational force, we talk about the force of attraction between two bodies, out of these bodies,if one body is the earth the gravitational force is called force of gravity.Thus, the force of gravity is the special case of the force of gravitation.When a stone is released from the top of tower, it falls towards the ground.Similarly, if a body thrown upward, its speed slows down. The speed becomes zero when the body reaches a certain height, the body returns to the ground. Tf a stone is released at the top of a deep well, it goes into the earth. This implies that the earth attracts every body lying near its surface and on its surface towards its centre. The force of attraction of the earth on the bodies which lie on its surface(or near its surface) is called gravity or force of gravity.
Not only the earth but also all the planets or other heavenly bodies have gravity.The gravity of a body depends upon its mass. The gravity of the moon is about 1by6 times the gravity of the earth.

Centripetal force

• If a body moves in a circular path with constant angular velocity,it has a constant linear velocity along the circumference of the circular path.When the body moves along the circle, the direction of velocity changes at every point on the circle. However,the magnitude of the velocity remains the same.The change in direction of the velocity of the particles moving in the circle implies that the particles has an acceleration.If a particle has an acceleration,a force must have acted upon it cause the acceleration.This implies that if a body is moving uniformly in a circle,a force is acting on the body at every point on the circle. The force acting on the body is such that, at every point, the force changes the direction of the velocity keeping the magnitude constant.This is possible only if the force acts perpendicular to the direction of the velocity.The direction of the velocity of the body at any point on the circle is tangent to the circle at the point.Thus,it is clear that the force acting on the body moving in a circle at a point is always perpendicular to the tangent to the circle at the point. This means that the force acting on the body moving in a circle is always along the radius and towards the centre of the circle is called centripetal force. The acceleration thus produced on the body due to the centripetal force is called centripetal acceleration.
• Thus, the centripetal force on a body is defined as the external force which causes the boy to move in a circular path with a constant velocity,and acts along the radius and towards the centre of the circular path.

Collision

A person walking with his heads down may collide with another person walking against him. A car or vehicle may collide with another car or vehicle in an accident. The billiards balls collide each other in a billiard game. The gas molecules contained in a box (or a vessel) collide each other and with the walls of the vessel. Similarly,when two charged particles moves towards each other, their paths are deviated.All of these events are called collisions. There are a large number of examples of collisions occurring in our daily life. In fact , we may knowingly or unknowingly undergo collisions many times during our every day activities.

For example,if we happen a strike against a wall in a room by mistake, it is also called collisions.The collision takes place for every short period of time during the collision, the colliding particles or bodies exchange their momentum and energy in a short interval of time .A collision is said to occur if the particles or bodies come in physical contact with each other or if the path of a particle is affected by each other.

Discovery of charge

Historically, discover of change should be attributed to ancient Greek philosopher who noted when certain material is rubbed with fur,it acquires property of attracting light objects such as, dust particles,cork bits etc. Thales of milteus,around 600BC wrote in his writing that his property in much more seen in amber when rubbed with wool.
Gilbert(1540-1603), physicists to queen Elizabeth,showed that many other substance are similarly affected by friction, say glass rod rubbed with silk,sealing wax with flannel, vulcanise with fur do do in marked degree.
It should be noted that in ab ore process, there are two suitable materials, which are brought in close contact by rubbing and on separating they acquire the property of attracting light objects.In order to describe this effect we say that the material is electrified or charged.It means, the bodies have acquired a quantity called charge or electricity. The process of charging bodies by rubbing is called electrification. The electrification is from Greek world which means other.
It is clear that during electrification two suitable materials are required and both of them are charged,As charges are produced in the bodies by rubbing,it is also called frictional electricity.

Antiparticles

Electrons,Which are positively charged, and protons, which are negatively charged.Physicists cannot only imagine such particles; they have actually detected them and measured their properties .Such particles as positive and negative protons are called antiparticles.
The first of the antiparticles discovered was the positive electron or proton.It was predicted before it was actually detected. In 1928 ,the British mathematical physicists P.A.M.Dirac formed a theory to explain the behaviour of electrons in a way, which would agree with the agree with the theory was completely unexpected. The theory predict that there should was completely of negative energy,We everywhere,they would not ordinarily be detectable suppose, however,that an energetic gamma-ray photon gave one of these energy to lift it to a condition of positive energy. It would leave behind a hole(some what like the holes in the transistor).According to the theory,the hole would behave like a particle with a positive charge and with a mass equal t that the electrons-a positron.Thus the gamma ray photon would have produced a pair of observable particles an electron and a positron.

Internal energy

Total energy contained in the system is called its internal energy. It is denoted by E or U. Internal energy of a system is continued by different components like kinetic energy, potential energy, rotational energy,vibrational energy, transitional energy, band energy, molecular energy etc. Among them value of components cannot be determined accurately. So the exact value of the system cannot be determined accurately. In thermodynamic calculation of the exact value of internal energy of a system has no importance. We need the change in internal energy of a system for different thermodynamic calculation and we can determined the change in internal energy of a system experimentally.
Suppose a thermodynamic system is changed from state1 to stat2.Let E1 and E2 be the internal energy of initial and final states respectively.Then change in internal energy is total energy is given by
Total energy=E2-E1
The change in internal energy of a system is state function because it depends only upon the initial and final states of system, it does not depends upon the path in which that a change is carried.

Conductors and semiconductors

Conductors:
In the case of conductors,there is no forbidden band and the valence band and conduction band overlap each other.Here plenty of force electrons are available for electric conduction. The electrons from valence bond freely enter in the conduction band.The most important point in conductors is that due to absence of forbidden band, there is no structure to establish holes. The total current in conductors is simply a flow of electrons.

Semi-conductors:
In the semi-conductors,the forbidden band is very small. Germanium and silicon are example of semi-conductors. In the germanium forbidden band is of the order of 0.7ev while in case of silicon, the forbidden band is of material is one 1ev.Actually,a semi-conductor material is one whose electrical properties lies between insulators and good conductors.At zero degree kelvin there are no electrons in conduction band and the valence band is completely filled. When a small amount of energy is supplied, the electrons can easily jump from valence band to the conduction band.For example, when the temperature is increased,the forbidden band is decreased so that some electrons are liberated into the conduction band .In semi-conductors,the conductivities are of the order of 10^2mho-metere.

Kinetic theory of gases

Postulates of kinetic theory
The kinetic theory of gases states that a gas consists of a large number of particles called molecules. The moles are randomly moving continuously in all directions and hence collide with themselves and with walls of the container is due to the continuous bombardment of the molecules. The following assumptions are known as postulates of kinetic theory of gases.

1. A gas consists of a large number of small particles called molecules.
2. The molecules are perfectly elastic spheres.
3. The volume of molecules is negligible as com rared to the volume of gas.
4. The molecules of the gas are continuously moving randomly in all directions and with all velocities.
5. There exists no force of attraction between the molecules.
6. The molecules of the gas collide elasticity with themselves and with the walls of the container.
7. The effects of gravity on the molecules is negligible.
8. A molecule moves in straight line between collions.
   
9. The average kinetic energy of the gas molecules is proportional to the absolute temperature.
   

Physical quantity

when we want to study about a natural phenomenon, we may want make a hypothesis and to search for a mathematical relation. The mathematical relation contains many parameters concerning the phenomenon. The various parameters appearing in the mathematical relation are called physical quantities. For examples,to study the motion of a planet around the sun, various parameters to be studied may be the time period for one revolution, the angular velocity of the planet, the distance between the planet and the sun, the mass of of the planet etc.
The most common physical quantities in our daily life are mass, volume, area,length,time etc.In fact a standard unit should have the following characteristics:

1. The standard unit should be portable size.
2. It should be well defined.
3. It should be universal;i.e. it should be accepted by all the con tries in the world.
4. It should be easily available everywhere in the world.
5. It should be independent of time and place.
6. It should be independent of physical condition such as temperature,pressure etc.
7. It should be cheaply available.
   

Circular Motion: Exploring Characteristics, Mathematical Description, and Real-World Applications

When a car takes a turn, it moves in a circular path. If a stone is attached at one end of the string and the string is whirled, the stone moves in a circle. When a cyclist takes a turn at a corner of a road, he moves in a circular path. All the above motions are called circular motions. The motion of an airplane ta ling a turn, motion. The motion of the planets around the sun., the motion of the satellites around the planets, the motion of an object placed on a turning table, etc. The circular motions, in fact, are very common in our daily life.

The circular motion is an accelerated motion. The body under the circular motion has constant speed however its direction is changing continuously. If either the speed or the speed or both are changing, the body is said to be accelerated. Thus a body moving in a circle has acceleration due to a change in the direction of its velocity but not due to a change in the magnitude of the velocity. The direction of acceleration of the body moving in the circle is always along the radius and towards the radius and towards the center of the circle.

Characteristics of Circular Motion:

Circular Path: Circular motion occurs when an object follows a curved path with a fixed radius. The object continuously repeats its motion, traversing the same path over and over again.

Constant Speed: In ideal circular motion, the object moves at a constant speed along the circular path. Despite the change in direction, the magnitude of the object's velocity remains constant.

Centripetal Force: Circular motion requires a force called the centripetal force, directed towards the center of the circular path. This force enables the object to continuously change its direction without moving away from the path.

Mathematical Description of Circular Motion:

To describe circular motion mathematically, several key concepts and formulas come into play:

Angular Velocity (ω): Angular velocity represents the rate at which an object rotates or moves along a circular path. It is measured in radians per second (rad/s) and is given by the formula:

ω = Δθ / Δt

where Δθ is the change in angle and Δt is the change in time.

Tangential Velocity (v): Tangential velocity refers to the instantaneous linear velocity of an object moving in a circular path. It is given by the formula:

v = r * ω

where r is the radius of the circular path and ω is the angular velocity.

Centripetal Acceleration (a): Centripetal acceleration represents the acceleration of an object moving in a circular path. It is directed towards the center of the circle and is given by the formula:

a = v^2 / r

where v is the tangential velocity and r is the radius of the circular path.

Centripetal Force (F): The centripetal force is the force required to keep an object moving in a circular path. It is directed towards the center of the circle and is given by the formula:

F = m * a

where m is the mass of the object and a is the centripetal acceleration.

Real-World Applications:

Circular motion has numerous practical applications across various fields:

Planetary Motion: Circular motion is observed in the orbits of planets around the Sun. The gravitational force acts as the centripetal force, keeping the planets in their stable circular paths.

Amusement Park Rides: Rides like carousels, Ferris wheels, and roller coasters involve circular motion. The circular paths and controlled speeds create thrilling and enjoyable experiences for riders.

Automotive Engineering: Vehicles navigate curves and turns through circular motion principles. The centripetal force allows the vehicles to maintain stability and remain on the road while negotiating bends.

Sports: Circular motion is evident in sports such as discus and hammer throwing, where athletes generate centripetal force to propel the objects in circular paths.

Mechanical Systems: Circular motion is utilized in various mechanical systems, including engines, turbines, and motors. Understanding circular motion helps optimize the design and performance of these systems.

Conclusion:

Circular motion is a fundamental concept with diverse applications in physics, engineering, and everyday life. It involves objects moving along curved paths with a fixed radius, maintaining constant speed and direction due to the centripetal force acting towards the center of the circle. By understanding the mathematical description

Radioactivity

RADIOACTIVITY:In 1896 Becquerel discovered that uranium gave out some type of radiations that could affects a photographic plate. In 1898,pi re curie and Marie curie succeed in extracting from pitch blend(a uranium ore) a new substance which was many millions of times more active in emitting radiations than uranium.They named this elements as radium. The substances which emit these radiations are known as radioactivity. The phenomenon of spontaneous emission of powerful radiations exhibited by the heavier elements found in nature is called natural radioactivity. On the other hand, the phenomenon of spontaneous emission of radiations from the elements much lighter than those occur by modern techniques or artificial transmutation of elements is known as artificial or induced radioactivity.Radioactivity is the spontaneous disintegration of nucleus of an atom from which may be emitted some or all the following radiations.

1. Alpha particles
2. Bi ta particles
   
3. Gama rays
   

The alpha particles radiations consist of stream of particles which are nus lie of helium atom, where as bi ta particles are electrons and Gama rays are electronegative waves of nuclear origin consisting of neutral particles. It should be remembered that the radioactive elements while radiating radiations is transformed into a new element which, of course, is again radioactive. this change is irreversible. The emission of radiations from radioactive substance is not instantaneous but it is a prolonged process other wise the phenomenon of radioactivity could not be discovered at all.

Physics and Society

Pollution

pollution is the direct or indirect changes in the components of the environment that deteriorates the environment .environment can be divided into air pollution ,water pollution ,land pollution or soil pollution.

These pollution are unfavourable and due to extra new substances or energy added unnecessary.These changes apposed the useful parts of the surroundings and they were weaken or destroyed .
Types of pollution :

1. Air pollution
   
2. Noise or sound pollution
   
3. Land pollution
   
4. water pollution
   

1. Air pollution

There are oxygen ,nitrogen ,carbon dioxide,argon and others harmful gases.fore in elements or substances if mixed with them their original quality are destroyed. then atmospheric air is said Tobe polluted.By the increasing of air pollution day by day it is badly effect our environment.the various pollutants emitted by the exhausts of motor vehicles like trucks,buses ,tempo, etc are produces carbon dioxide gas,carbon monoxides gas,sulphur dioxide gas etc and unburnt hydrocarbons like octane,nitrogen oxides etc .similarly, industries are also sources of smoke,dust solid waste.

The main causes of air pollution is due to smoke, dust and very harmful gases co,co2,so2 etc.
The main effects of air pollution are;polluted air contain harmful particles,because of this many people suffer from respiratory and eye disease.

2.Noise pollution
The unwanted ,ha rash and loud sound is known as noise. The disturbance produced in environment by the undesirable loud sound of various kinds is called noise pollution.In short noise pollution is unwanted sound, crowd of people,radio,loud speakers on open field,means of transport ion and machines and other instruments are the man source of noise.

the main cause of noise pollution are busy market area,industrial area,produce much sound that makes noise pollution .the engines of vehicles as likes as aeroplane,buses,cars etc and it is horns of vehicles also produce noise pollution.

The main effects of noise pollution are:it effects to the lose our hearing power permanently,it affects our health that causes blood pressure etc.noise also affects our mind,which is harm our physical parts of the body.It also disturbs our digestive system,sleeping habit that cause several diseases .It makes us lazy and disturb our normal life.

3.water pollution
Different activities of people and wastes from industries pollute water.when pollutants change physical and chemical property of water dirties quality as different from original one. Thus the change of the state of water in such a way that it is not useful to use by using being is called water pollution.

The main causes of water pollution are:wastes of hospital, laboratory, industry and work shop contain harmful chemical and wastes.If they are mixed with water sources they pollute water sources.

The main effects of water pollution are:polluted water generates bad smell to its surroundings.It pollutes settlement area and even the environment.

We control water pollution by wastes water of industries and factories should be property treated before distance to outside either land or water sources. similarly solid and waste, dirty water of hospital, laboratory and industries should be processed properly for controlling water pollution programs should be launched at central and local levels.

4.Soil or land pollution
We live on the land and land have their own value in environment. People throw out wastes such as broken glasses, dirty things and other materials that are not useful to them. some of these waste materials that or bi degradable decay after sometime and mixed with solid . such water materials do not pollute the environment . the other materials such as plastic, broken glass, vehicles and mechanics are not degradable and remain on the land for longer period that chemical properties of the land. Thus detericration of land due to accusation of waste materials on it is called land pollution.

The main effects of land pollution id due to chemical fertilizer and poisonous like pesticide is harmful to plants,animals and other living beings. In accordance of food cycle,such poisons are transformed to human beings through the food they eat. land pollution affects natural setting of land and cultural heritage such as religious place, monastery and other heritage sites.