Types of Magnetism

Types of Magnetism

Before discussing the different types of magnetism we need clear up a few definitions which are used to categorise the types of magnetism.

Magnetic Suseptibily

As the magnetic field increases, the magnetic flux increases. We denote magnetic field intensity by H and magnetic flux by B the constant of proportionality is μ₀ this is known as the magnetic permitivity

In a vacuum, μ₀ has a value of 4π x 10^-7 H m^-1 in SI units

For other materials this proportionality is expressed with the relative permitivity, μ_r

The susceptibility χ is defined in terms of the relative permitivity. χ = (μ_r - 1)

Ferromagnetism

  alignment of electron spins

Anti-Ferromagnetism

Ferrimagnetism  

Ferri magentic material have two sets of magnetic dipole moments pointing in opposite directions. The magnetic moments do not cancel each other out becauses the dipole moment in one direction is smaller than the other. On a B-H graph ferrimagnetism is like ferromagnetism.

Diamagnetism

Diamagnetic materials are composed of atoms that have no net magnetic moments. However, when exposed to a field a weak negative magnetisation is produced which causes repulsion instead of attraction. Diamagnetic materials have negative susceptibilty with magnetitude of around -10 to -10^-4

Many common materials are diamagnetic and hence In the presence of very strong magentic fields the repulsion caused by diamagnetism can cause objects to levitate even frogs.

Paramagnetism

Paramagnetic materials such as liquid oxygen and aluminium show a weak magnetic attraction when placed near a magnet. Some atoms or ions in the material have a net magentic moment due to unpaired electrons in partially filled orbitals. In the presence of a field, there is a partial alignment of the atomic magnetic moments in the direction of the field resulting in a net positive magnetisation and positive susceptibility.

In a strong magnetic field, paramagnetic materials become magentic and will stay magnetic while the field is present. When the strong magnetic field is removed the net magnetic alignment is lost and the magnetic dipoles relax to a random motion.

Magnetism

Introduction Of Magnetism

The ancient Greeks knew that a type of rock with magnetic properties known as lodestone or magnetite attracted iron. The compass, an important device for navigation, has a suspended magnet which aligns parallel to the magnetic field produced by the Earth and as a result points to the  North Pole. The compass was documented as early as 1040. The Ching Tsung Yao describes how iron can be magnetised by heating and quenching in water. It is known that the Vikings used Lodestone to navigate. By the end of the twelfth century, Europeans were using this simple compass to aid navigation. A steel needle stroked with such a "lodestone" became "magnetic" as well.

In 1600, William Gilbert (also known as Gilberd) of Colchester proposed an explanation in his work De Magnet for the operation of the compass and that The Earth itself was a giant magnet, with its magnetic poles some distance away from its geographic ones (i.e. near the points defining the axis around which the Earth turns). He made an experimental model of the earth by creating a .

Properties of Magnets

William Gilbert also experimented on bar magnets and found the following properties:

A magnet will always have two poles which we call arbitrarily North and South. I the magnet is broken in two this will create two new magnets with North and South poles. If a bar magnet is broken in two, at the fracture new north and south poles are formed at the point of fracture.

• Like pole repel each other. If a N pole is brought close to the north pole of a second magnet a repulsive force will be felt. Similarly if a South pole is brought close to the South pole of another magnet, the two magnets will repel each other.
• Unlike poles attract and will stick together.
• Magnets attract iron rich materials and like poles and the repulsion between like poles can be reduced if a strip of iron is placed between them.

Comets

Comets

Comets are very beautiful when they pass close to the sun but they are merely giant balls of frozen water mixed with cosmic dust. There is also a small percentage of ammonia, methane, and CO₂. These chunks are theorised to have originated from the forming of giant planets like Saturn, Jupiter, Neptune, and Uranus, and each comet is usually the size of one of the Rocky Mountains. There are four parts to a comet: nucleus, coma, plasma tail, and dust tail. The nucleus is the only permanent part of the comet. Although it has never been seen, there is no doubt of its existence. The brightness of the comet can depend on how large the nucleus' diameter is since these spherical forms can scatter sunlight like a mirror.

Comets have a wide range of orbital periods, ranging from a few years to hundreds of thousands of years. Short-period comets originate in the Kuiper Belt, or its associated scattered disc,[1] which lie beyond the orbit of Neptune. Longer-period comets are thought to originate in the Oort cloud, a cloud of icy bodies in the outer Solar System that were left behind during the condensation of the solar nebula. Long-period comets plunge towards the Sun from the Oort Cloud because of gravitational perturbations caused by either the massive outer planets of the Solar System (Jupiter, Saturn, Uranus, and Neptune), or passing stars. Rare hyperbolic comets pass once through the inner Solar System before being thrown out into interstellar space along hyperbolic trajectories.

Comets come from the outermost regions of the solar system called the Oort cloud, some 50,000 AU from the Sun.

The Sun's gravitational field is the dominant force out to around 2 light-years although beyond the Oort cloud there is still much that is not known beyond.

The structure of a comet

The Solar System

What is in the Solar System?

The Sun

The Sun is our nearest star. The Sun contains approximately 98% of the mass of the solar system and provides the gravitational force required to keep the planets orbiting around it. Solar energy is created deep within the core by nuclear fusion. Every second 700 million tons of hydrogen are converted into Helium. And the energy produced by this conversion is what gives energy to almost everything that lives on the Earth.

The  Planets

In order of distance from the Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The inner planets (Mercury, Venus, Earth and Mars) are formed from solid material while the outer planets (Jupiter, Saturn, Uranus and Neptune) are formed from gas and liquid.

The Discovery of Neptune

(Since antiquity, the planets Mercury, Venus, Mars, Saturn, Jupiter).

Neptune could have been discovered a lot earlier than it was, Galieo had seen it

Newtons law of gravity allowed the solar system to be modelled with great accuracy, however observations of Uranus showed that it did not behave entirely as predicted. The only planet to be discovered was Uranus in 1781 by Music Teacher, William Herschel who believed it to be a comet and named it Georgium Sidus (George's Star) in honour of King George III.

 Accurate data for the orbits of the other planets was available but the data for Uranus did not fit with the calculated results. The anomalous were caused by another large object and Neptune was discovered by calculating where a planet would have to be to produce the anomalous behavior of Uranus. This was the first planet to be discovered by mathematics.

The first accurate predictions of Uranus' motion were published in 1792. Within a few years, it was obvious that there was something wrong with the motion of the planet, as it did not follow the predictions. Attempts to calculate improved tables using the latest mathematical techniques were unable to fit all the observations, ancient and modern, to a single orbit. A commonly accepted suspicion during the next few years was that Newton's Law of Gravity, although accurate out to the orbit of Saturn, might not work in the same way at greater distances; but by the late 1830's it seemed at least equally likely that there was an unknown body lying beyond the orbit of Uranus.

Neptune was discovered on September 23, 1846 by the astronomer Johann Galle and his student Heinrich d'Arrest, after only thirty minutes of searching the sky, within a degree of the position predicted by the Urbain Le Verrier. This was the high-water mark of Newtonian physics: to be able, given the laws of physics and the peculiar motion of one object, to reach out into the depths of space and uncover a previously hidden object and caused an even greater sensation than the discovery of Uranus

There were a number of observations of Neptune prior to its discovery as a planet, but once again, mostly at times when it was near a stationary point, and hence nearly motionless relative to the stellar background. In fact, the first observations were made by Galileo, he even noted that the object which we now know as Neptune seemed to have moved relative to the nearest star, but failed to follow up his observations, and hence lost the opportunity to discover Neptune 168 years before Herschel discovered Uranus.

A planet had been discovered by mathematics, was it possible that other planets might be found in this way? A search at both ends of the solar system followed. Close to Mercury, the precession of the line of apsides (the imaginary line that runs along the major axis of the orbit). Unfortunately, even in the 1840's, it was obvious that the calculated rate of precession for the line of apsides was too small however, it might have conceivebly been caused by a smaller planet than Mercury that orbited on an orbit closer than Mercury. The planet was christened Vulcan (hence the name for the hot planet that Spock supposedly came from in the Star Trek series). The planet does not exist even though it has been observed on two occassions. The precession an effect of special and general relativity. It is ironic, given the early suposition that Uranus that the orbits errors were due to a flaw in Newtonian physics and the subsequent discovery that they were due to Neptune, that in the case of Mercury, the situation was exactly opposite. Initial speculations centred on a unknown planet and the solution involving a failure of Newtonian physics.

Around some of the planets there are moons which orbit the planet.

Dwarf Planets

At the time of writting, the IAU has officially reconises three Dwarf planets however there are other objects which may be designated as dwarf planets.

Ceres - located in the main asteroid belt was discovered in Jan 1st, 1801 by Giuseppe Piazzi. It is the smallest of the dwarf planets.

Pluto is not now considered to be a planet but a dwarf planet. 

2003 UB₃₁₃ formerly known as Xena is now officially named Eris - the largest known dwarf planet

Sedna - the coldest most distant place known in the solar system; possibly the first object in the long-hypothesized Oort cloud.

Types of Capacitors

Types of Capacitors

The below is the Types of Capacitors

Electrolytic Capacitors

Aluminum electrolytic capacitors are made by layering the electrolytic paper between the anode and cathode foils, and then coiling the result. The process of preparing an electrode facing the etched anode foil surface is extremely difficult. Therefore, the opposing electrode is created by filling the structure with an electrolyte. Due to this process, the electrolyte essentially functions as the cathode.

Electrolytic capacitors are soaked in a liquid or paper impregnated with a liquid which is not a dielectric but when a voltage is applied creates a layer of aluminium oxide which acts a the dielectric. The reaction is dependent on the polarity of the applied voltage. If the polarity is reversed the capacitor will produce a gas and is likely to explode or burst because of the pressure inside and so are not suitable for alternating current applications. 

MEMs Capacitors

Micro Electro-Mechanical System(MEMs) are small devices manufactured from Silicon. Plate capacitors can be fabricated which show small changes in capacitance a the separation of the plates is increased or decreased. The small devices can be used as sensors and gyroscopes. 

Common types of devices are the parallel plate capacitors for position sensing. Also, interpenetrating comb-like structures, in which the capacitance may be altered using by moving one comb relative to another, either in the transverse direction or longitudinal direction. Because of their small size, the variation in capacitance is very small, of the order 10^-15 F. (femto-Farads).

Tantalum Capacitors

Tantalum capacitors are polarised and have low voltage ratings like electrolytic capacitors. They are expensive but very small so they are used where a large capacitance is needed in a small size such as mobile phones or laptop computers. These capacitors have increasingly become an important as the demand for ever smaller electronic gadgets has grown. Columbite-tantalite - coltan, for short, the ore from which tantalum is refined is mined in Australia, Egpyt. The high demand for the ore has also financed civil wars in the Democratic Republic of the Congo. A UN security council report charged that a great deal of the ore is mined illegally and smuggled over the country's eastern borders by militants from neighboring Uganda, Burundi and Rwanda providing the revenue to finance the military occupation of the Congo. 

Super capacitors

Super capacitors are capacitors which have the ability to store large amounts of charge, and therefore energy, in a very small volume. Energy storage is by means of static charge rather than of an electro-chemical process that is inherent to the battery. Applying a voltage differential on the positive and negative plates charges the super capacitor. This concept is similar to an electrical charge that builds up when walking on a carpet. The super capacitor was first conceived in 1957 but now research is focused on using these as a light weight power sources as an alternative for batteries. the super capacitor crosses into battery technology by using special electrodes and some electrolyte. Super capacitors could find applications such as temporary back-up power supplies in the electrical power grid or providing the initial burst of energy to get electric cars moving. 

Thermodynamic Potentials

Thermodynamic Potentials

Thermodynamic potentials are used to measure the energy of a system in terms of different variables because often we can only measure certain properties of the system. For example we might know the pressure and temperature of system but not the volume or the entropy. Thermodynamic potentials allow us to measure more state variables of the system.

The thermodynamics potentials are the  internal energy,enthalpy, Gibbs Free Energy and the Helmholtz Free Energy.

These different potentials can be remembered by writing them in the form of a grid.

From the first law of thermodynamics, the internal energy, is given by

dU = dQ + dW

dU = T dS + P dV

From H = U + P V, then dH = dU + dP V + PdV (using the chain rule).

The first column of the first row contains just the internal energy U, to obtain the enthalpy, we must add P V. In the second row, the Helmholtz Free F energy is the internal energy, U minus T S, finally in the second column of the second row, the Gibbs Free Energy G we must add P V and take away T S.

We wish to have a number of expressions for the energy of a system in terms of different variables, for we shall sometimes know the pressure and temperature of a system, but not the volume or entropy; or we might know the volume and temperature but not the pressure and entropy. In most cases, we shall know only a few relevant quantities and will wish to find out many more. This leads to the following definitions two or more thermodynamic quantities:

U

H = U + P V

F = U - T S

G = U + P V - T S

Using Thermodynamic Potentials

From the first and second laws of thermodynamics, dU and dQ are not obviously measurable. Therefore we need thermodynamic manipulation to get useful properties from what is measurable, i.e., P, V and T. Thermodynamics quantities are more commonly defined in terms of partial differentials. For example:

Example of Thermodynamic Potentials

Good examples of thermodynamic potentials include electrolysis or

They are thermodynamic potentials because each can be found as a result of differentiating.

Heat Engines

Heat Engines

A heat engine is any machine which converts heat into useful work for example, a steam engine or a car engine. Real heat engines are complex and there are many ways of converting heat energy into useful work. We can abstract and generalise the workings of any heat engine into three parts:

• The Hot Resevoir - heat energy is created by some process such as combustion of a fuel to provide the heat energy.
• The working body - converts the heat energy into work. In real heat engines, the conversion process is never 100% efficient, so the work output is always less than the heat energy supplied. However we frequently idealise and assume reversibility.
• The cold resevoir - the energy that cannot be turned into work is dumped and goes to heat up the cold resevoir. In practice, the cold resevoir is usually the atmosphere. We also assume that the temperature of the cold resevoir does not increase, it has an infinite heat capacity.

Schematic diagram of a heat engine.

Assume that a heat engine starts with a certain internal energy U, intakes ΔQ_i heat from a heat source at temperature T_i , does work ΔW , and exhausts heat ΔQ_f into a the cooler heat reservoir with temperature T_f. With a typical heat engine, we only want to use the heat intake, not the internal energy of the engine, to do work, so ΔU=0. The first law of thermodynamics tells us:

ΔU=0 = ΔQ_i - ΔQ_f - ΔW

To determine how effectively an engine turns heat into work, we define the efficiency, η, as the ratio of work done to heat input:

η = ΔW/ΔQ_i = (ΔQ_i-ΔQ_f)/ΔQ_i

= 1 - ΔQ_f/ΔQ_i

Because the engine is doing work, we know that ΔW >0, so we can conclude that ΔQ > 0. Both and are positive, so the efficiency is always between 0 and 1:

Efficiency is usually expressed as a percentage rather than in decimal form. That the efficiency of a heat engine can never be 100% is a consequence of the Second Law of Thermodynamics. If there were a 100% efficient machine, it would be possible to create perpetual motion: a machine could do work upon itself without ever slowing down.

Nuclear Fission

Introduction Of Nuclear Fission

Nuclear Fission is the breakup of a large nucleus into two smaller nuclear fragments. Accompanying the break-up of the large nucleus is the release of energy determined by the mass defect.

Liquid-Drop Model of the Nucleus

A model of how the nucleus breaks apart is called the 'liquid-drop' model of the nucleus. An incoming neutron collides with a large nucleus and causes it to become unstable, the large nucleus vibrates like a large water drop and can cause the nucleus to split into two smaller fragments

Chain Reactions

A nuclear chain reaction.

Critical Mass

Even though an incoming neutron can initiate the emission of more than one outgoing neutron, the outgoing neutrons may completely miss other nuclei, therefore, to create a chain reaction, one must increase the probability of hitting other nuclei. To insure that the probability of a neutron colliding with a nuclei, the number of nuclei must be increased, or the density of nuclei must be increased. When there are so many fissile nuclei that chance of initiating a chain reaction is equal to one, we speak of a critical mass.

Nuclear Power

Capacitors

Capacitors

A capacitor is an electronic device for storing charge. Capacitors can be found in almost any complex electronic device. They are second only to resistors in their There are many different types of capacitor but they all work in essentially the same way. A simplified view of a capacitor is a pair of metal plates separated by a gap in which there is an insulating material known as the dielectric. This simplified capacitor is also chosen as the electronic circuit symbol for a capacitor is a pair of parallel plates as shown below.

Various types of capacitor

The symbol for an unpolarised capacitor 

Normally, electrons cannot enter a conductor unless there is a path for an equal amount ofelectrons to exit. However, extra electrons can be "squeezed" into a conductor without a path to exit if an electric field is allowed to develop in space relative to another conductor. The number of extra free electrons added to the conductor (or free electrons taken away) is directly proportional to the amount of field flux between the two conductors.

In this simplified capacitor the dielectric is air. When a voltage, V is applied to the terminals of the capacitor, electrons flow on to one of the plates and are taken off the other plate. The total number of electrons in the capacitor remains the same. There are just more on one the negative plate and fewer on the positive plate.

 

Errors and Uncertainty

Errors and Uncertainty

Error has to do with uncertainty in measurements that nothing can be done about. If a measurement is repeated, the values obtained will differ and none of the results can be preferred over the others. Although it is not possible to do anything about such error, it can be characterized. For instance, the repeated measurements may cluster tightly together or they may spread widely. This pattern can be analysed systematically.

When we measure something the measurement is meaningless without knowing the uncertainty in the measurement. This leads us to the idea of errors in measurement. Other factors such as the conditions under which the measurements are taken may also affect the uncertainty of the measurements. Thus when we report a measurement we must include the maximum and minimum errors in the measurement.

As an example, take measuring the height of a person, the measure may be accurate may have a scale of 1 mm. But depending on how the person being measured holds them self during the measurement we might be accurate in measuring to the nearest cm.

Generally, errors can be divided into two broad and rough but useful classes: systematic and random.

Systematic errors are errors which tend to shift all measurements in a systematic way so their mean value is displaced. This may be due to such things as incorrect calibration of equipment, consistently improper use of equipment or failure to properly account for some effect. In a sense, a systematic error is rather like a blunder and large systematic errors can and must be eliminated in a good experiment. But small systematic errors will always be present. For instance, no instrument can ever be calibrated perfectly.

Other sources of systematic errors are external effects which can change the results of the experiment, but for which the corrections are not well known. In science, the reasons why several independent confirmations of experimental results are often required (especially using different techniques) is because different apparatus at different places may be affected by different systematic effects. Aside from making mistakes (such as thinking one is using the x10 scale, and actually using the x100 scale), the reason why experiments sometimes yield results which may be far outside the quoted errors is because of systematic effects which were not accounted for.

Random errors are errors which fluctuate from one measurement to the next. They yield results distributed about some mean value. They can occur for a variety of reasons.

• They may occur due to lack of sensitivity. For a sufficiently a small change an instrument may not be able to respond to it or to indicate it or the observer may not be able to discern it.

• They may occur due to noise. There may be extraneous disturbances which cannot be taken into account.

• They may be due to imprecise definition.

• They may also occur due to statistical processes such as the roll of dice.
  
  Random errors displace measurements in an arbitrary direction whereas systematic errors displace measurements in a single direction. Some systematic error can be substantially eliminated (or properly taken into account). Random errors are unavoidable and must be lived with.
  
  

Voltage

Voltage

Voltage is the energy per unit charge or the difference in potential between two points. The correct name for voltage is the potential difference or p.d.. The S.I. unit of voltage is the Volt [V], but from the definition, it can also be expressed as [N.m.C-1].

Voltage in Electronic Circuits

• Voltage is supplied by the battery (or power supply).
  
• Voltage is used up in components, but not in wires.
  
• We say voltage across a component.
  
• Voltage is measured with a voltmeter, connected in parallel.
  

The Link between Current and Voltage

The link between current and voltage is as follows, it is not possible to have a current (a flow of charge) without a difference in potential.

Secondly, in order for the current to flow there has to be a closed path or circuit around which the charge can flow. A disconnected battery has a voltage but there is no current because there is no closed path for the electrons to flow around.

Hydrodynamic Model of Voltage

Often, an analogy between electricity and water is made. The voltage is like the pressure, and the current is analogous to the flow of the water through the pipes.

It is easy to imagine, that when we increase the pressure of the water the flow rate will increase and it is the same with electricity. If we increase the voltage, then the rate of flow of charge willl increase, which is the current.

There is another factor which is important in the link between current and voltage and that is the resistance. The resistance is the coefficient of proportionality which determines the current for a given voltage.

For example if we have a 6 V battery and we set up a circuit which allows a current to pass through a resistor. The current flowing through the resistor can be measured using an ammeter. Let's say the ammeter gives a reading of 0.02 A. The resistance of the resistor would be 6 V/(0.02 A) = 300 Ω

This leads us to the famous equation V =IR, which is also known as Ohm's Law.

Circular Motion

Circular Motion

Circular motion is commonly seen in both microscopic and large systems. Motion of the electron, planetary motion and rotation of tyres are common examples of circular motion. What is circular motion? It is a type of motion exhibited by a particle or set of particles moving around a fixed point at a constant distance from that point.

A body that travels an equal distances in equal amounts of time along a circular path has a constant speed but not constant velocity. This is because velocity is a vector and thus it has magnitude as well as direction

The velocity of P is directed along the tangent at P. The speed remains constant but the velocity has changed. We know that if the velocity changes with time then the ball on the string is also accelerating.

The Radian

angles can be measured in radians as well as degrees. The angle in radians is defined by. If s = r then θ=1 rad. Therefore, 1 rad is the angle subtend at the center of a circle by an arc equal in length to the radius. When s =2π r then θ=2 π radians=360°. Therefore, 1 rad = 360°/2 π=57.3°
θ = s/r 

Since we are often dealing with angles and trigonometric functions, a useful approximation that is often used is that for small angles of &theta, sin θ and tan θ = θ where θ is measured in radians.

The plasma universe

The plasma universe


It is estimated that 99% of the matter in the observable universe is in the plasma state...hence the expression "plasma universe." (The phrase "observable universe" is an important qualifier: roughly 90% of the mass of the universe is thought to be contained in "dark matter," the composition and state of which are unknown.) Stars, stellar and extragalactic jets, and the interstellar medium are examples of astrophysical plasmas. In our solar system, the Sun, the interplanetary medium, the magnetospheres and/or ionospheres of the Earth and other planets, as well as the ionospheres of comets and certain planetary moons all consist of plasmas.

The plasmas of interest to space physicists are extremely tenuous, with densities dramatically lower than those achieved in laboratory vacuums. The density of the best laboratory vacuum is about 10 billion particles per cubic centimeter. In comparison, the density of the densest magnetospheric plasma region, the inner plasmasphere, is only 1000 particles per cubic centimeter, while that of the plasma sheet is less than 1 particle per cubic centimeter.

The temperatures of space plasmas are very high, ranging from several thousand degrees Celsius in the plasmasphere to several million degrees in the ring current. While the temperatures of the "cooler" plasmas of the ionosphere and plasmasphere are typically given in degrees Kelvin, those of the "hotter" magnetospheric plasmas are more commonly expressed in terms of the average kinetic energies of their constitutent particles measured in "electron volts." An electron volt (eV) is the energy that an electron acquires as it is accelerated through a potential difference of one volt and is equivalent to 11,600 degrees Kelvin. Magnetospheric plasmas are often characterized as being "cold" or "hot." Although these labels are quite subjective, they are widely used in the space physics literature. As a rule of thumb, plasmas with temperatures less than about 100 eV are "cold," while those with temperatures ranging from 100 eV to 30 keV can be considered "hot." (Particles with higher energies--such as those that populate the radiation belt--are termed "energetic.")

Plasmas - the fourth state of matter

Plasmas - the 4 state of matter

A plasma is a hot ionized gas consisting of approximately equal numbers of positively charged ions and negatively charged electrons. The characteristics of plasmas are significantly different from those of ordinary neutral gases so that plasmas are considered a distinct "fourth state of matter." For example, because plasmas are made up of electrically charged particles, they are strongly influenced by electric and magnetic fields while neutral gases are not. An example of such influence is the trapping of energetic charged particles along geomagnetic field lines to form the Van Allen radiation belts.

In addition to externally imposed fields, such as the Earth's magnetic field or the interplanetary magnetic field, the plasma is acted upon by electric and magnetic fields created within the plasma itself through localized charge concentrations and electric currents that result from the differential motion of the ions and electrons. The forces exerted by these fields on the charged particles that make up the plasma act over long distances and impart to the particles' behavior a coherent, collective quality that neutral gases do not display. (Despite the existence of localized charge concentrations and electric potentials, a plasma is electrically "quasi-neutral," because, in aggregate, there are approximately equal numbers of positively and negatively charged particles distributed so that their charges cancel.)

Thermal energy

What is Thermal Energy

Thermal Energy is the kind of energy that is related to and/or caused by heat. When thermal energy is applied to a substance, the average velocity the particles or molecules which make up the substance increases -- and it gets warmer!

Example of Thermal energy

When you boil a pot of water, you are contributing thermal energy or heat to the bottom of the pot. This thermal energy is then transferred to the water inside the pot. As the water molecules
move faster, they begin to get hotter. As they move faster and faster, each one tries to leap away from its neighbors and into the surrounding air to form of water vapor, or steam. Once the water starts boiling, it turns into steam very quickly!

Creation of Thermal Energy

Thermal energy is the total internal kinetic energy of an object due to the random motion of its atoms and molecules. It is sometimes confused with internal energy or thermodynamic energy.

They consist of the sum of the internal kinetic energy (thermal energy) and the potential energy of an object. You may need to make sure which definition a teacher or book is using.

Kinetic Theory of Matter

The Kinetic Theory of Matter states that matter consists of atoms or molecules in random motion. Those moving particles can transfer their kinetic energy to other nearby particles. The total kinetic energy of all the particles in an object make up the thermal energy of that object.

Temperature and heat

Temperature and heat are related to thermal energy.

• Temperature is defined as the average kinetic energy of all the atoms or molecules in an object.
• Heat is defined as the flow of thermal energy from an object of one temperature to an object of another temperature. You feel the flow of heat when warm air from a furnace reaches you.

Gamma-rays

Gamma-Rays

Gamma-rays have the smallest wavelengths and the most energy of any other wave in the electromagnetic spectrum. These waves are generated by radioactive atoms and in nuclear explosions. Gamma-rays can kill living cells, a fact which medicine uses to its advantage, using gamma-rays to kill cancerous cells.

Gamma-rays travel to us across vast distances of the universe, only to be absorbed by the Earth's atmosphere. Different wavelengths of light penetrate the Earth's atmosphere to different depths. Instruments aboard high-altitude balloons and satellites like the Compton Observatory provide our only view of the gamma-ray sky.


Gamma-rays are the most energetic form of light and are produced by the hottest regions of the universe. They are also produced by such violent events as supernova explosions or the destruction of atoms, and by less dramatic events, such as the decay of radioactive material in space. Things like supernova explosions (the way massive stars die), neutron stars and pulsars, and black holes are all sources of celestial gamma-rays.

Gamma-ray bursts can release more energy in 10 seconds than the Sun will emit in its entire 10 billion-year lifetime! So far, it appears that all of the bursts we have observed have come from outside the Milky Way Galaxy. Scientists believe that a gamma-ray burst will occur once every few million years here in the Milky Way, and in fact may occur once every several hundred million years within a few thousand light-years of Earth.

Studied for over 25 years now with instruments on board a variety of satellites and space probes, including Soviet Venera spacecraft and the Pioneer Venus Orbiter, the sources of these enigmatic high-energy flashes remain a mystery.

By solving the mystery of gamma-ray bursts, scientists hope to gain further knowledge of the origins of the Universe, the rate at which the Universe is expanding, and the size of the Universe.

Friction

Friction

One reason why the law of conservation of energy only works in theory is because of friction. When you push an object over a horizontal plane it should, theoretically, never stop. But friction keeps slowing it down until it's at rest.

The force of friction between two bodies depends on the magnitude of the perpendicular forces of the surfaces in contact. This perpendicular force is known as the normal force and the ratio of the frictional force to the normal force is known as the coefficient of friction. The normal force of an object on a horizontal plane is the weight of the object.

The coefficient of friction vary on the materials in contact. If you went down on a water slide with no water it probably wouldn't be much fun because you would be going so slowly, that is if you were moving at all. When there's water there is much less friction between you and the slide so you end up sliding down very fast and smoothly. Friction is used to slow and stop many amusement rides including roller coasters and the free fall .

There are many kinds of friction. One type is static friction. Static friction is between two solid bodies with respect to each other. Static friction prevents the motion of one object to the other until the applied force is greater than the static friction between them. To understand this we'll use a heavy box on the floor as an example. You try to push the box with say a force of 50 newtons but the box doesn't budge one bit. This means that the force you used, 50 newtons, was not enough to overcome the static friction. The minimum force needed to start moving the box is known as the starting friction. Once the box is moving the friction between the box and the floor decreases. The friction of an object in motion is called, kinetic or sliding friction.

When a ball rolls over a surface the frictional force is usually less than if it were sliding over the surface. The friction of any rolling object is called rolling friction. The frictional force of an object moving through a fluid like water or air, is called fluid friction.

The Law of Conservation of Energy

The Law of Conservation of Energy

Law of conservation of energy states that the energy can neither be created nor destroyed but can be transformed from one form to another.

Energy in a system may take on various forms (e.g. kinetic, potential, heat, light). The law of conservation of energy states that energy may neither be created nor destroyed. Therefore the sum of all the energies in the system is a constant.

The most commonly used example is the pendulum:

The formula to calculate the potential energy is:

PE = mgh

The mass of the ball = 10kg
The height, h = 0.2m
The acceleration due to gravity, g = 9.8 m/s^2
Substitute the values into the formula and you get:

PE = 19.6J (J = Joules, unit of energy)

The position of the blue ball is where the Potential Energy (PE) = 19.6J while the Kinetic Energy (KE) = 0.

As the blue ball is approaching the purple ball position the PE is decreasing while the KE is increasing. At exactly halfway between the blue and purple ball position the PE = KE.

The position of the purple ball is where the Kinetic Energy is at its maximum while the Potential Energy (PE) = 0.

At this point, theoretically, all the PE has transformed into KE> Therefore now the KE = 19.6J while the PE = 0.

The position of the pink ball is where the Potential Energy (PE) is once again at its maximum and the Kinetic Energy (KE) = 0.

We can now say and understand that:

PE + KE = 0 PE = -KE

The sum of PE and KE is the total mechanical energy:

Total Mechanical Energy = PE + KE

Universal Law of Gravitation

Definition of Universal Law of Gravitation

According to Newton’s Universal law of Gravitation, every particle in the universe attract every other particle with a force directly proportional to the product of their masses and inversely proportional to the square of distance between them. The direction of this gravitational force is along the line joining the particles.



Newton's law of universal gravitation extends gravity beyond earth. Newton's law of universal gravitation is about the universality of gravity. Newton's place in the Gravity Hall of Fame is not due to his discovery of gravity, but rather due to his discovery that gravitation is universal. All attract each other with a force of gravitational attraction. Gravity is universal. This force of gravitational attraction is directly dependent upon the masses of both objects and inversely proportional to the square of the distance which separates their centers.Newton's conclusion about the magnitude of gravitational forces is summarized symbolically as

Since the gravitational force is directly proportional to the mass of both interacting objects, more massive objects will attract each other with a greater gravitational force. So as the mass of either object increases, the force of gravitational attraction between them also increases. If the mass of one of the objects is doubled, then the force of gravity between them is doubled. If the mass of one of the objects is tripled, then the force of gravity between them is tripled. If the mass of both of the objects is doubled, then the force of gravity between them is quadrupled; and so on.

Since gravitational force is inversely proportional to the separation distance between the two interacting objects, more separation distance will result in weaker gravitational forces. So as two objects are separated from each other, the force of gravitational attraction between them also decreases. If the separation distance between two objects is doubled (increased by a factor of 2), then the force of gravitational attraction is decreased by a factor of 4 (2 raised to the second power). If the separation distance between any two objects is tripled (increased by a factor of 3), then the force of gravitational attraction is decreased by a factor of 9 (3 raised to the second power).

Second Law of Thermodynamics

Second Law of Thermodynamics

The second law of thermodynamics is a general principle which places constraints upon the direction of heat transfer and the attainable efficiencies of heat engines. In so doing, it goes beyond the limitations imposed by the first law of thermodynamics. It's implications may be visualized in terms of the waterfall analogy.

Qualitative Statements: Second Law of Thermodynamics

The second law of thermodynamics is a profound principle of nature which affects the way energy can be used. There are several approaches to stating this principle qualitatively. Here are some approaches to giving the basic sense of the principle.

1. Heat will not flow spontaneously from a cold object to a hot object.

2. Any system which is free of external influences becomes more disordered with time. This disorder can be expressed in terms of the quantity called entropy.

3. You cannot create a heat engine which extracts heat and converts it all to useful work.

4. There is a thermal bottleneck which contrains devices which convert stored energy to heat and then use the heat to accomplish work. For a given mechanical efficiency of the devices, a machine which includes the conversion to heat as one of the steps will be inherently less efficient than one which is purely mechanical.