Category: Physics Notes PPT

Temperature requirements

 

Temperature is a system consisting of the average kinetic energy of particles. After the sufficient temperature is reached, according to the Lawson criterion, the energy of accidental collisions occurring within the plasma is large enough to overcome the Coulomb barrier which might lead the particles to fuse together.

 

There are two effects that lower the actual temperature required. Some nuclei at the sufficient temperature would actually have much higher energy than 0.1 MeV, while others would be much lower. For most of the fusion reactions, nuclei in the high-energy tail of the velocity distribution matters. The second effect is quantum tunneling. The nuclei do not actually possess enough energy to overcome the Coulomb barrier fully. If they have the approximate required energy, they can tunnel through the remaining barrier. 

 

Confinement

 

The key problem in achieving thermonuclear fusion is the confinement of the hot plasma. , the plasma cannot be in direct contact with any solid material in high temperature and therefore, has to be located in a vacuum. At high pressures, the plasma tends to expand and some force is required to act against it. This force can be the gravitation in stars, magnetic forces in magnetic confinement fusion reactors, or inertia.

 

Gravitational confinement

 

Gravitational force is capable of confining the fuel well enough to satisfy the Lawson criterion. The mass needed is massive that gravitational confinement can be found only in stars. In stars which satisfy the mass required, after the supply of hydrogen gets over in their cores, their cores (or a shell around the core) start fusing helium to carbon. In the heaviest stars (at least 8–11 solar masses), the process is continued until some of their energy is made by fusing lighter elements to iron. Iron has one of the highest binding energies. Thus reactions producing heavier elements are endothermic in nature. Therefore significant amounts of heavier elements are formed only in supernova explosions.

 

All the elements that are heavier than iron have some potential energy to release. The heavier elements can produce energy during the process of being split again back toward the size of the iron, in the process of nuclear fission happening at the end of element production. The energy which is released during nuclear fission is stored energy, probably stored even billions of years before, during stellar nucleosynthesis. 

 

Magnetic confinement

 

Electrically charged particles follow magnetic field lines. This is applicable to fuel ions. A strong magnetic field can, therefore, trap the fusion fuel. The toroidal geometries of tokamaks, stellarators and open-ended mirror confinement systems are magnetic configurations that can be used.

 

The other ways to do this are;

 

• Inertial Confinement – rapid pulse is dispensed to achieve optimal conditions

 

• Electrostatic Confinement – the electrostatic field is used to confine ions

 

Why is this not practically possible?

 

Chain reactions are almost impossible to occur. Hence it’s much easier to control and stop them than fission reactions. So logically, it is better to tap into this source rather than using fission reactions. 

 

Unfortunately, the possibility of harnessing this energy in the near future is very less. It might not be possible for at least two decades from now. A rather disturbing thought that now prevails is, in case this is not a foreseeable and assuring future, the number of resources spent on research could have been used for other renewable sources of energy.

The word Electo in electrostatic is for electric charges and static means at rest. So, the study of force between two like or alike charges is called electrostatic force.

Any stable atom always contains the electrostatic force of attraction. An electrostatic force is also known as the Coulombic force. It is the force of attraction between two opposing charges, i.e., protons and electrons. Here, the strong electrostatic force of attraction between them stabilizes the atomic particle.

On this page, we will define electrostatic force and discuss the real-life applications of electrostatic force in detail.

Define Electrostatic Force

An electrostatic force or the Coulombic force is defined as the force of attraction or repulsion between two like and unlike charges, respectively. The two charges bear equal magnitude but opposite charges and are separated by some distance.

An imaginary line exists between these two charges to mark their distance from each other. Also, the charges have the square of the distance between them.

 

Now, we will learn to find the electrostatic force between the two charges, viz: q1 & q2 in the following context:

Electrostatic Force

Take a balloon and a piece of wool. Now, rub the balloon with this piece of wool, a heat generated on the balloon’s surface.

Bring a few pieces of paper near to this balloon, you see that pieces of paper get attracted to the balloon. It is because an electrostatic force of attraction builds between the balloon and the pieces of paper.

Coulomb’s Law

We can quantify the electrostatic force between two charged particles by using Coulomb’s law. Coulomb’s law usually applies to point charges and gives a relationship between the electrostatic force, the magnitude of the charges, and the distance between them. According to this law, the force between the two particles is stated in the following manner:

Coulombic Force

A Coulombic force can be explained by the following equation:

[F alpha frac{q_{1}q_{2}}{r^{2}}]

Here,

q1 = a positive/negative charge or vice versa

q2 = a negative/positive charge or vice versa

r² = the distance between the two charges (both of equal and opposite magnitude)

Now, removing the sign of the proportionality constant, we rewrite the equation as;

[F=K frac{q_{1}q_{2}}{r^{2}}]

Here, k is the constant and it is known as the electrostatic constant or the force constant. 

Define Coulomb Constant

The Coulomb constant was named after the French physicist named Charles-Augustin de Coulomb who introduced Coulomb’s law.

The value of ‘k’ is approximately equal to 8.987 5517923 (14) x 10⁹ kg.m³.s^-2.C^-2

According to the above equation (2), F disappears when r approaches infinity. Thus, at infinity or a large distance, the electrostatic force reaches zero. Scientifically, the range of F is infinite.

The work done W by the force F on a particle is the product of the force and the displacement d. The equation is as follows:

W= F x d

The work done in moving the charged particle from one position to another is independent of the path taken. Hence, the electrostatic force is conservative in nature.

Examples of Electrostatic Force

• The rubbing of clouds produces electrostatic charges. These charges get neutralized by passing through the atmosphere until they reach the neutral ground. We perceive this phenomenon as lightning.

• After combing your hair, if you bring the wet comb close to a piece of paper, an electrostatic force of attraction between the comb and trace of the paper develops, and the paper sticks with the comb.

• A silk shirt sticks to the body because of charged particles on the shirt. The same phenomenon applies to a woollen pullover when taking off.

• Getting out of a vehicle on a warm, dry day and touching its door gives us charges.

• Grains of sugar get attracted to the inside surface of a container due to electrostatic forces.

• The surface of the truck carries a lot many charges and when any vehicle passes the truck, the electrostatic force generates between the charged particles on the truck’s surface and the charges present in the air. 

Point to Note:

Electrostatic forces are present at places where charged particles interact through a polar medium. Hence, electrostatic forces are particularly crucial for ceramic materials in polar media viz: water and ethanol. The electrostatic forces are usually stronger and have a longer range than all other surface forces.

Applications of Electrostatic Force

The electrostatic force carries multiple real-life applications, and a few of these are discussed below:

A cyclotron is a kind of circular particle accelerator. In a cyclotron, a charged particle is accelerated along a spiral path under the action of a static magnetic field and an alternating electric field. The charged particle is inserted in a cyclotron such that its direction of motion is perpendicular to the static magnetic field. The magnetic field causes the particle to make rotations and the electric field accelerates the particle after each rotation. The electric field is generated by a high-frequency alternating voltage. The frequency of the alternating voltage is matched with the cyclotron frequency for the charged particle and generally, it is kept constant. 

Frequency of Rotation of a Charged Particle in a Uniform Magnetic Field

The theory of cyclotron is based on the interaction of a charged particle with electric and magnetic fields. The magnetic force on a particle of charge q, moving with velocity v due to a uniform magnetic field B is given by,

F = q v x B

When a charged particle moves perpendicular to a constant magnetic field with speed v, the magnitude of the magnetic force is,

F = q

νν

B sin 90°

F = q

νν

B

This force acts in a direction perpendicular to both the velocity of the particle and the magnetic field.

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The Circular Path of a Charged Particle

The particle starts to rotate in a circular path of radius r such that the magnetic force serves as the centripetal force of that circular path. The centripetal force

FcFc has magnitude,

Fc= mν2rmν2r

Here, m is the mass of the particle and r is the radius of the circular path. The centripetal force is equal to the magnetic force i.e.

FcFc= Fmν2rmν2r

= qννBνν

= qBrmqBrm

The angular velocity (cyclotron angular frequency) is given by,

ωω= νrνr

ωω= qBmqBm

The frequency of the rotation namely cyclotron frequency is,

f = ω2πω2π

f = qB2πmqB2πm

This is the cyclotron frequency formula.

Operating Principle of Cyclotron

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• In a cyclotron, two hollow “D” shaped electrodes are placed face to face with a small gap, inside a vacuum chamber. An alternating voltage is applied between the “dees” across the gap. A uniform magnetic field is applied perpendicular to the plane of the electrodes. The “dees” have a cylindrical space for the particles to move.

• Charged particles are injected at the center of the cylindrical space (shown by a dot in the figure). If the particles would have a constant velocity, they would rotate in circles of constant radii. But an alternating voltage of high frequency is applied across the gap. The frequency is set such that the charged particles make a semicircle during a single cycle of the alternating voltage. In other words, the frequency of the ac voltage must match with the cyclotron frequency of the particles given by the cyclotron formula,

f = qB2πmqB2πm

Here, q is the charge, is the mass of the particle and B is the magnetic field strength.

• Each time a particle completes a semicircle inside a dee and approaches the other dee, the polarity of the voltage flips. The particle gets accelerated towards the other dee due to the electric field created by the ac voltage and its velocity increases.

• Since the frequency remains constant, the particle starts to move in a circle of a larger radius. The particle’s trajectory takes the shape of a spiral of increasing radius. With each full cycle, the radius increases, and the velocity also increases. This process continues until the radius of the trajectory approaches the radius of the cylinder and the accelerated particles are passed through an exit at the end of the cylinder. The radius of the cylinder must be set such that the desired velocity of the particles can be reached.

 

Applications of Cyclotron

Cyclotrons are much more effective than linear accelerators because cyclotrons accelerate the particles several times in a single set up and due to their cylindrical shape, less space is required as compared to linear accelerators. Some of the uses of cyclotron are listed below,

• Cyclotrons are widely used to accelerate charged particles in nuclear physics experiments and use them to bombard atomic nuclei.

• For radiation therapy in the treatment of cancer, different cyclotrons are used.

• Cyclotrons can be used for nuclear transmutation (change of the nuclear structure).

Limitations of Cyclotron

• Neutral particles (e.g. neutron) do not interact with electric or magnetic fields. So, cyclotrons cannot be used to accelerate them.

• Since electrons have very small mass, their speed increases very rapidly and soon the resonance between the high voltage and the particle becomes lost. Hence, a cyclotron cannot accelerate electrons.

• Cyclotrons can accelerate particles to speeds much less than the speed of light (in the non-relativistic regime).

What Exactly is a Cyclotron?

A cyclotron is an apparatus for increasing the energy of charged particles or ions. E.O Lawrence and M.S Livingston devised it in 1934 to examine the nuclear structure. The cyclotron boosts the energy of charged particles by using both electric and magnetic fields. Cross fields are named such because both fields are perpendicular to each other.

Charged particles accelerate outwards from the centre of a cyclotron along a spiral route. A static magnetic field keeps these particles on a spiral route, while a rapidly shifting electric field accelerates them.

Cyclotron Principle of Operation

• A charged particle beam is accelerated in a cyclotron by applying a high-frequency alternating voltage between two hollow “D”-shaped sheet metal electrodes inside a vacuum chamber called the “dees.”

• Dees are situated between the poles of an electromagnet, which produces a perpendicular static magnetic field B.

• The Lorentz force perpendicular to the particle’s direction of motion causes the particle’s path to bend in a circle due to the magnetic field.

• Between the dees, an alter
  nating voltage of several thousand volts is supplied. By creating an oscillating electric field in the region between the dees, the voltage accelerates the particles.

• The voltage is set at a frequency that allows particles to complete one circuit in a single cycle. The frequency must be tuned to the particle’s cyclotron frequency to achieve this situation.

Cyclotron Frequency Expression

f = [frac{qB}{2pi m}]

• The magnetic field strength is denoted by the letter B.

• q is the particle’s electric charge.

• m is the relativistic mass of the charged particle.

Particle Energy Expression

The particles’ energy is determined by the magnetic field’s strength and the diameter of the dees.

The formula for calculating the centripetal force required to keep the particles in a curved path is:

Fc = [frac{mnu ^{2}}{r}]

Lorentz’s force FB on the magnetic field B provides the force.

F[_{B}] = q[nu] B

Equating the equations we get,

[frac{mnu ^{2}}{r}]

[nu] = [frac{qBR}{m}]

Hence, the output energy of the particle is given by the expression

E = [frac{q^{2}B^{2}R^{2}}{2m}]

Cyclotron Applications

These were the best sources of high-energy beams for nuclear physics investigations for decades. These are, however, still used in this type of research.

Is there Anything that Cyclotron Can’t do?

• Because electrons have such a little mass, a cyclotron cannot accelerate them.

• The use of a cyclotron to accelerate neutral particles is not possible.

• Due to the relativistic effect, it cannot accelerate positively charged particles with enormous masses.

 Did You Know?

• To accelerate particles with relativistic speed, synchrocyclotrons (frequency of the voltage is adjusted after each cycle), and isochronous cyclotrons (the magnetic field is adjusted) are used. These modifications are made to balance the increasing mass of the accelerating particle as its speed tends to the speed of light. 

• Ernest O. Lawrence invented the first-ever cyclotron at the University of California, Berkeley in 1932. It was a 69 cm diameter machine with a maximum energy of 4.8 MeV. He was awarded the Nobel Prize in 1939 for this invention. He also invented a synchrocyclotron in 1945. 

• The largest cyclotron is at TRIUMF (Canada’s particle accelerator centre), which has a diameter of 18 m and maximum energy of 520 MeV.

• The Superconducting Ring Cyclotron (SRC) can produce high-intensity beams of accelerated particles. At RIKEN, a large research institute in Japan, there is an SRC of 19 m diameter. It has six superconducting sectors.

In physics, a lens is defined as a device that either focuses or disperses the light beam falling on it using refraction. Based on this concept, the lenses are classified into two types – converging lenses that concentrate parallel rays of light falling on them and diverging lenses that cause parallel rays of light to spread out. No matter whether converging or diverging, both types of lenses are marvels of optical physics and used to create a sharp, magnified, and clear image of the object placed on one side of them. Although the principal purpose of all the lenses is to magnify or we can say make images appear larger than their actual size, still there is a remarkable difference in the images formed by them. For instance, an image formed by a converging lens differs from one formed by a diverging lens. There are several aspects like shapes, physical dimensions, etc., of a lens that impact the behaviour of a light beam falling on it, and also the characteristics of the image formed. To understand the physics of the concept of lenses and images formed by them, we need to know about lens formula. It is a key term around which our optical physics often revolves.

 

What is Lens Formula?

Based on the physics concept stating that lenses are formed by coupling two spherical surfaces together, lenses are of two types:

Characteristics of images created by these lenses differ depending on the aspects of lenses and object’s distance from these lenses. It is where the lens formula comes into the action. As per optical physics, lens formula relates the distance of an object (u), the distance of an image (v), and the focal length (f) of the lens. Applicable for both the convex and concave lenses, the lens formula is given as:

1/v – 1/u = 1/f  

Where, 

v = Distance of image formed from the optical center of the lens. 

u = Distance of object from the optical center of the lens.

f = focal length of the lens.  

 

Lens Formula Derivation

Convex Lens

Consider a convex lens with O be the optical centre, and F be the principal focus with focal length f. Now, let AB be the object kept perpendicular to the principal axis and at a distance beyond the focal length.                      

As the object is perpendicular to the principal axis, the image will also be perpendicular to the principal axis. To find out the location of the image formed, draw a perpendicular from point A’ to point B’ on the principal axis. On doing this, we can see that the ΔABO and ΔA’B’O are similar as shown in the figure. 

So, A′B′/AB = OB’/OB (as ΔABO and ΔA’B’O are similar) … (1)

Also, ΔA’B’F and ΔOCF are similar

So, A’B’/OC = FB’/OF 

But, OC = AB

Therefore, A’B’/AB = FB’/OF 

From the above equations, we get:

OB’/OB = FB’/OF = (OB’ – OF)/ OF

Now, by using the sign convention, OB = -u, OB’ = v, and OF = f, we can say:

v/-u = (v – f) /f

=> vf = – uv + uf or uv = uf – vf

Diving both sides by uvf, we will have:

uv / uvf = (uf / uvf) – (vf/ uvf)

Hence, 1/f = 1/v – 1/u 

This is the required lens formula.

 

Concave Lens

Let AB be the object perpendicular to the principal axis and at a distance more than the focal length (f) of the convex lens. We will see that the image A’B’ is erect, virtual, and formed on the same side as the object.                   

Now, from the figure, we can consider that:

OF1 is the focal length (f),

OA is the object distance (u),

OA is the image distance (v),   

and ΔOAB and ΔOA’B’ are similar

 ∵ Angle BAO = Angle B’A’O = 900, vertex O is common for both the triangles

So, Angle AOB = Angle A’OB’

Therefore, Angle ABO = Angle A’B’O

And, A’B’ / AB = OA’ / OA                                              … (1)

Again, ΔOCF1 and ΔF1A’B’ are similar

So, A’B’/ OC = A’F1/ OF1

But from the diagram, we can see that OC = AB

A’B’ / AB = A’F1/ OF1 = (OF1 – OA’)/ OF1

A’B’ / AB = (OF1 – OA’)/ OF1                                    … (2)

From equation (1) and equation (2), we get

OA’ / OA = (OF1 – OA’)/ OF1       

– v / -u = (-f – – v)/ -f                                                                      

v/ u = (-f + v)/ -f   

– vf = – uf  + uv                        … (3)                                                                

Dividing equation (3) by uvf

– 1/u = – 1/v + 1/f

Hence, 1/f = 1/v – 1/u 

This is the required lens formula.

Concave Mirror

A concave mirror, which is also known as a converging mirror, consists of a reflecting surface that has been recessed inward (away from the incident light). The concave mirror can reflect the light inward to one focal point. They are used for focusing light. In a concave mirror, the image type depends on the distance between the object and the mirror.

Convex Lens

A convex lens is a type of lens that is thicker at the center and thinner at the edges. An optical lens is built using two spherical surfaces which if bent outwards will be considered as a convex lens. These types of lenses are used for converging a beam of light and focusing it to a point at the other side.

How to Find the Focal Length of a Concave Mirror – Class 12?

The following are the ways by which students can find the focal length of a concave mirror using a convex lens.

• A concave mirror can be termed as a spherical mirror consisting of a reflecting surface that is curved inwards, and it also follows the laws of reflection of light.

• The light rays that are coming from a distant object are considered to be parallel to each other.

• If the image formed is real, inverted, and very small in size, then it is believed that the rays of light which are parallel to each other meet the point in the front of the mirror.

• The image that is formed by the concave mirror is considered to be real and can be obtained on the screen.

• ‘f’ is used to express the difference between the principal axis P and the focus F of the concave mirror.

Materials Required to Find the Focal Length of Concave Mirror Using Convex Lens

The following are the list of materials that are required to find the focal length of a concave mirror using a convex lens.

• A concave mirror

• A measuring scale

• A screen holder

• A mirror holder

• A mirror stand  

Procedure to Find the Focal Length of Concave Mirror Using Convex Lens

• The distance between the distinct objects selected should be more than 50ft.

• The object and the concave mirror that is placed on the mirror stand should be facing each other.

• The screen must be fixed in front of the reflecting surface of the mirror in order to obtain a clean and sharp image.

• The distance between the screen and the concave mirror can be determined by using a meter scale. This distance is the same as the focal length of the given concave mirror.

• This above process should be repeated three times to obtain the average of the focal length.   

How to Find the Focal Length of a Convex Mirror Using a Convex Lens?

The following are the ways that should be followed to find the focal length of a convex mirror using a convex lens.

• The convex mirror is thicker in the middle and is thinner at the edges. It is also known as a converging mirror.

• The refracted rays that are coming from the parallel beam of light converge on the other side of the convex mirror.

• The image that is obtained by the focus of the lens will be real, inverted, and very small in size.

• ‘F’ is known as the focal length, which is considered as the distance between the optical center of the lens and the principal focus.

• There is a possibility of the image being formed on the screen if the image formed by the mirror is real.

Materials Required to Find the Focal Length of Convex Mirror Using a Convex Lens

The following are the list of materials that are used to find the focal length of a convex mirror using a convex lens.

Procedure to Find the Focal Length of a Convex Mirror Using a Convex Lens

• Try to arrange the lens and screen on the wooden bench without disturbing them.

• The lens should be placed in a holder facing the distant object.

• The holder should be placed with the screen on the bench.

• The position of the screen should be such that the sharp image of the distant object is obtained easily without any difficulties.

• The difference between the screen and the position of the lens is considered to be the focal length of the convex mirror.

• After completing the above steps, shift the focus towards other distant objects in order to calculate the focal length of the convex mirror.

How is the Concave Mirror Different from a Convex Mirror?

The concave and convex mirrors are different from each other and therefore, give different results. If the outer surface of a spherical mirror is painted then it is known as a concave mirror whereas if the inner surface of a spherical mirror is painted, then it is known as a convex mirror. The concave mirror and convex mirror are also known as the converging mirrors and the diverging mirrors respectively. In the case of the concave mirror, only the inner surface is reflexive whereas, in the case of a convex mirror, only the outer surface is reflexive.

In the case of the concave mirror, the focal length is positive whereas the focal length is negative in the case of a convex mirror. Concave mirrors can form both real and virtual images and thus can be obtained on the screen whereas convex mirrors can form only virtual images which cannot be obtained on the screen. The center of curvature and the reflecting surface fall on the same side in a concave mirror whereas in the case of a convex mirror the center of curvature and the reflecting surface fall on the opposite sides. Vehicle headlights, shaving mirrors, and torches use concave mirrors whereas convex mirrors are used as rear view mirrors in bikes and cars. Magnified images of the object are obtained from a concave mirror whereas a convex mirror provides a wider view of the object.

Conclusion

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at the same place. 

The collection of physical phenomena associated with the presence and motion of matter with an electric charge is known as electricity. Lightning, static electricity, electric heating, electric discharges, and many other popular phenomena are all related to electricity.

An electric field is generated by the presence of an electric charge, which can be positive or negative. A magnetic field is generated by the movement of electric charges, which is known as an electric current.

Electric Charge

The presence of charge causes an electrostatic force, in which charges exert a force on each other, an effect that was recognized in antiquity but not fully understood. Touching a light ball suspended from a string with a glass rod that has been charged by rubbing with a cloth will charge it. When a similar ball is charged with the same glass rod, it repels the first: the charge serves to separate the two balls. Two balls charged with a rubbed amber rod repel each other as well. When one ball is charged by a glass rod and the other by an amber rod, the two balls are attracted to each other.

Electric Current 

An electric current is the movement of an electric charge, and its strength is normally measured in amperes. A current is made up of all moving charged particles, the most common of which are electrons. Nevertheless, any charge in motion is a current. Electrical current can pass through certain objects, such as electrical conductors, but not through an electrical insulator.

Electric Dipole Moment

The electric dipole moment is a measurement of a system’s overall polarity or the separation of positive and negative electrical charges within it. The coulomb-meter (Cm) is the SI unit for electric dipole moment; however, the debye is a widely used unit in atomic physics and chemistry (D).

The first-order concept of the multipole expansion defines an electric dipole in theory; it consists of two equal and opposite charges that are infinitesimally close together, even though actual dipoles have separated charges.

Point charges are charged point particles with an electric charge. An electric dipole is made up of two point charges, one with charge +q and the other with charge q, separated by a distance d. (a simple case of an electric multipole). The electric dipole moment, in this case, has a magnitude of p=qd

and is driven from the negative to the positive charge. Since this quantity is the distance between either charge and the center of the dipole, some authors can break d in half and use s = d/2, resulting in a factor of two in the description.

Since a quantity with magnitude and direction, such as the dipole moment of two point charges, can be expressed in vector form, a better mathematical concept is to use vector algebra.

P=qd

where d denotes the vector of displacement from the negative to the positive charge. Also, the electric dipole moment vector p points from the negative to the positive charge.

The electrical point dipole, which consists of two (infinite) charges that are only infinitesimally separated but have a finite p, is an idealization of this two-charge system. This value is used to calculate the polarization density.

Dielectric

An electrical insulator that can be polarized by an applied electric field is known as a dielectric (or dielectric material). When an electric field is applied to a dielectric material, electric charges do not flow through it as they would in an electrical conductor, but instead change slightly from their average equilibrium positions, resulting in dielectric polarization. Positive charges are displaced in the direction of the field by dielectric polarization, whereas negative charges move in the opposite direction (for example, if the field is moving in the positive x-axis, the negative charges will shift in the negative x-axis). This induces an internal electric field within the dielectric, which decreases the total field. As weakly bound molecules make up a dielectric, the molecules become polarized and reorient so that their symmetry axes match with the field.

Dielectric properties are the analysis of how electric and magnetic energy is stored and dissipated in materials. Electronics, optics, solid-state physics, and cell biophysics all depend on dielectrics to describe different phenomena.

Dielectric Polarization

A substance is made up of atoms in the traditional approach to the dielectric model. Each atom is made up of a cloud of negative charge (electron) that is bound to and surrounds a positive point charge in the center. The charge cloud is skewed in the presence of an electric field.

Using the superposition theorem, this can be reduced to a simple dipole. The dipole moment is a vector quantity that characterizes a dipole. The action of the dielectric is determined by the interaction between the electric field and the dipole moment. The atom returns to its original state when the electric field is withdrawn. The time it takes to do so is referred to as the relaxation time; it is an exponential decay. 

The behavior of the dielectric is determined by the relationship between the electric field E and the dipole moment M, which can be described by the function F defined by the equation:

M=F(E)