Monday 3 December 2012

TRANSFORMER

TRANSFORMER
THE DEVICE WHICH IS USED TO CHANGE THE VOLTAGE.
                                       OR
  A transformer is a power converter that transfers AC electrical energy through inductive coupling between circuits of the transformer's windings. A varying current in the primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic flux through the secondary winding. This varying magnetic flux induces a varying electromotive force (EMF), or "voltage", in the secondary winding. This effect is called inductive coupling.
If a load is connected to the secondary winding, current will flow in this winding, and electrical energy will be transferred from the primary circuit through the transformer to the load. Transformers may be used for AC-to-AC conversion of a single power frequency, or for conversion of signal power over a wide range of frequencies, such as audio or radio frequencies.
In an ideal transformer, the induced voltage in the secondary winding (Vs) is in proportion to the primary voltage (Vp) and is given by the ratio of the number of turns in the secondary (Ns) to the number of turns in the primary (Np) as follows:

\frac{V_\text{s}}{V_{\text{p}}} = \frac{N_\text{s}}{N_\text{p}}
By appropriate selection of the ratio of turns, a transformer thus enables an alternating current (AC) voltage to be "stepped up" by making Ns greater than Np, or "stepped down" by making Ns less than Np. The windings are coils wound around a ferromagnetic core, air-core transformers being a notable exception.
Transformers range in size from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used in power stations, or to interconnect portions of power grids. All operate on the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household ("mains") voltage. Transformers are essential for high-voltage electric power transmission, which makes long-distance transmission economically practical.

OHM'S LAW

ohm's law
 Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance, one arrives at the usual mathematical equation that describes this relationship:
I = \frac{V}{R}
where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.
The law was named after the German physicist Georg Ohm, who, in a treatise published in 1827, described measurements of applied voltage and current through simple electrical circuits containing various lengths of wire. He presented a slightly more complex equation than the one above (see History section below) to explain his experimental results.

Capacitor

CAPACITOR
the instrument which is used  to store the charges.
 A capacitor (originally known as condenser) is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric (insulator); . Capacitors are widely used as parts of electrical circuits in many common electrical devices.
When there is a potential difference (voltage) across the conductors, a static electric field develops across the dielectric, causing positive charge to collect on one plate and negative charge on the other plate. Energy is stored in the electrostatic field. An ideal capacitor is characterized by a single constant value, capacitance, measured in farads. This is the ratio of the electric charge on each conductor to the potential difference.it is used in any things like mobiles,toys and also there are many capacitor used in  motherboard of computer.
Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass, in filter networks, for smoothing the output of power supplies, in the resonant circuits that tune radios to particular frequencies, in electric power transmission systems for stabilizing voltage and power flow, and Photo-SMDcapacitors.jpg.

COLOUMB'S LAW

The law

Coulomb's law states that the magnitude of the Electrostatics force of interaction between two point charges is directly proportional to the scalar multiplication of the magnitudes of charges and inversely proportional to the square of the distances between them.
A graphical representation of Coulomb's law
If the two charges have the same sign, the electrostatic force between them is repulsive; if they have different sign, the force between them is attractive.
The scalar and vector forms of the mathematical equation are
|\boldsymbol{F}|=k_e{|q_1q_2|\over r^2}    and    \boldsymbol{F}=k_e{q_1q_2\boldsymbol{\hat{r}_{21}}\over r_{21}^2} ,   respectively.

An electric field


If the two charges have the same sign, the electrostatic force between them is repulsive; if they have different sign, the force between them is attractive.
The magnitude of the electric field force, E, is invertible from Coulomb's law. Since E = F Q it follows from the Coulomb's law that the magnitude of the electric field E created by a single point charge q at a certain distance r is given by:this law is used very much in the world for many things.it can not be challenge.
|\boldsymbol{E}|={1\over4\pi\varepsilon_0}{|q|\over r^2}.
An electric field is a vector field which associates to each point of the space the Coulomb force that will experience a test unity charge. Given the electric field, the strength and direction of a force F on a quantity charge q in an electric field E is determined by the electric field. For a positive charge, the direction of the electric field points along lines directed radially away from the location of the point charge, while the direction is towards for a negative charge.

COLOUMB'S LAW

HERE IS THE COLOUMB'S LAW
Coulomb's law or Coulomb's inverse-square law is a law of physics describing the electrostatic interaction between electrically charged particles. It was first published in 1785 by French physicist Charles Augustin de Coulomb and was essential to the development of the theory of electromagnetism. This law states that "The force of attraction or repulsion between two point charges is directly proportional to the product of magnitude of each charge and inversely proportional to the square of distance between them".[1][2] Coulomb's law has been tested heavily and all observations are consistent with the law.
 File:Coulomb.jpg
In 1785, the French physicist Charles Augustin de Coulomb published his first three reports of electricity and magnetism where he stated his law and this publication was essential to the development of the theory of electromagnetism.He used a torsion balance to study the repulsion and attraction forces of charged particles and determined that the magnitude of the electric force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.

as their are many scientist passed and are alive have shown their laws and their theories in every field.columb has also maked columbs law which has been accepted uptil now and can not be challenged.In 1769, Scottish physicist John Robison announced that according to his measurements, the force of repulsion between two spheres with charges of the same sign varied as x-2.06.

Defects of a lens

the defects of lens are following

Spherical Aberration

  • Light impinging on different areas of the spherical surface of the lens will not meet at precisely the same spot. The rays striking the lens farthest from the center will focus slightly closer to the lens than rays than strike the lens near its center.

Chromatic Aberration

  • Chromatic aberration results from the fact that a lens refracts or bends some colors of light more sharply than others. A lens bends violet light rays more sharply than green, and red suffers even less refraction. As a result, the lens tends to separate white light into its component colors, and a colorful halo results.

Comatic Aberration

  • Comatic aberration occurs when light rays from a distance impinge upon a lens at an angle rather than perpendicular to the plane of its disc. .
The Different Kinds of Lens Defects thumbnail

LENS FORMULA

 

convex lens formula
Let AB represent an object placed at right angles to the principal axis at a distance greater than the focal length f of the convex lens. The image A1B1 is formed beyond 2F2 and is real and inverted.
OA = Object distance = u
OA1 = Image distance = v
OF2 = Focal length = f
OAB and OA1B1 are similar


But we know that OC = AB
the above equation can be written as


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



Dividing equation (3) throughout by uvf

SNELL'S LAW

 Snell's law 
  Snell–Descartes law or the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water and glass.

Refraction of light at the interface between two media of different refractive indices, with n2 > n1. Since the velocity is lower in the second medium (v2 < v1), the angle of refraction θ2 is less than the angle of incidence θ1; that is, the ray in the higher-index medium is closer to the normal.
In optics, the law is used in ray tracing to compute the angles of incidence or refraction, and in experimental optics and gemology to find the refractive index of a material. The law is also satisfied in metamaterials, which allow light to be bent "backward" at a negative angle of refraction (negative refractive index).
Although named after Dutch astronomer Willebrord Snellius (1580–1626), the law was first accurately described by the Arab scientist Ibn Sahl at Baghdad court, when in 984 he used the law to derive lens shapes that focus light with no geometric aberrations in the manuscript On Burning Mirrors and Lenses (984).[1][2]
Snell's law states that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of phase velocities in the two media, or equivalent to the reciprocal of the ratio of the indices of refraction:
\frac{\sin\theta_1}{\sin\theta_2} = \frac{v_1}{v_2} = \frac{n_2}{n_1}
with each \theta as the angle measured from the normal of the boundary, v as the velocity of light in the respective medium (SI units are meters per second, or m/s) and n as the refractive index (which is unitless) of the respective medium.
The law follows from Fermat's principle of least time, which in turn follows from the propagation of light as waves.

Spherical Mirror Formula


Spherical Mirror Formula

The characteristics and location of an image formed by a spherical mirror can be determined from an equation which is called spherical mirror formula.
al-qasim-trust-Convex Mirror Formula 1
Concave mirror formula
To derive concave mirror formula consider fig. (14.4) where an object OA, is placed in front of a concave mirror. A ray of light starting from the end point A of the object and moving parallel to the principal axis strikes the mirror at the point E. it is reflected at E and passes through the principal focus F. A second ray also starting from A falls on the mirror at pole P. it is reflected by making an angle of reflection equal to the angle of incidence and intersects the first reflected ray at point B i. e., . Thus, point B is the real image of point A.
desk-top-class-mirror-1
al-qasim-trust-mirror-2

Generally, the distance of the object from the mirror is denoted by P and that of image as q. focal length of the mirror is denoted by f.
Therefore, the above equation can be written in the following manner:
al-qasim-trust-mirror-3

Convex Mirror Formula
Consider an object OA placed in front of a convex mirror (fig. 14.5). A ray of light starts from the end point A of the object. It moves parallel to the principal axis. It strikes the mirror at the point E and reflected in the direction EM. If this ray is produced backwards (in dotted lines), it meets the principal axis at the principal focus F. this ray appears to be diverged from F. another ray starting from end point ‘A’ falls on the pole P of the mirror and is reflected by making an angle of reflection equal to the angle of incidence. If this ray is produced backwards (in dotted lines), it intersects the first ray at the point B. thus, point B is the virtual image of ‘A’. if this process is repeated for other points of the object OA then the image IB of the object OA is obtained. This image is virtual, erect and diminished.
al-qasim-trust-Convex Mirror Formula
Using Fig. 14.5, we can prove that the relationship between the object distance p, from the pole, the image distance q from the pole and the focal length of convex mirror f is the same as given by Eq. 14.3 i.e.,
al-qasim-trust-mirror-4
This equation is known as a spherical mirror formula. Since in case of convex mirror, image is always virtual and according to sign conventions, distance of virtual image and focal length of convex mirror is taken as negative.

 

SPEED OF SOUND

SPEED OF SOUND
 The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at 20 °C (68 °F), the speed of sound is 343.2 metres per second (1,126 ft/s). This is 1,236 kilometres per hour (768 mph), or about one kilometer in three seconds or approximately one mile in five seconds.
In fluid dynamics, the speed of sound in a fluid medium (gas or liquid) is used as a relative measure of speed itself. The speed of an object (in distance per time) divided by the speed of sound in the fluid is called the Mach number. Objects moving at speeds greaterkly depends oy for a given ideald speed is slightly depependent on square root of the mean molecular weight of the gas, and affected to a lesser extent by the number of ways in which the molecules of the gas can store heat from compression, nd in gaxpressed in terms of a ratio of both density and pressure, these quantities cancel in ideal gases at any given te only the latter independent variables.
In common everyday speech, speed of sound refers to the speed oaves in air. However, the speed of sounstance to substance. Sound t in liquids aoli it does in air. It travels about 4.3 times as fast in water (1,484 m/s), and nearly 15 times on (5,1 The speed of shear waves is determined only by the solid material's shear modulus and density.

Sound intensity

INTENSITY IF SOUND
 Sound intensity or acoustic intensity (I) is defined as the sound power Pac per unit area A. The usual context is the noise measurement of sound intensity in the air at a listener's location as a sound energy quantity.
Sound intensity is not the ntity as sound pressure. Hearingly sensitive to  pre whis related to sound intensity. In consumer audio electronics, fferences  "intensity"

SOUND

SOUND
 Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation). Sound that is perceptible by humans has frequencies from about 20 Hz to 20,000 Hz. In air at standard temperature and pressure, the corresponding wavelengths of sound waves range from 17 m to 17 mm. During propagation, waves can be reflected, refracted, or attenuated by the medium.[2]
The behavior of sound propagation is generally affected by three things:
  • A relationship between density and pressure. This relationship, affected by temperature, determines the speed of sound within the medium.
  • The propagation is also affected by the motion of the medium itself. For example, sound moving through wind. Independent of the motion of sound through the medium, if the medium is moving, the sound is further transported.
  • The viscosity of the medium also affects the motion of sound waves. It determines the rate at which sound is attenuated. For many media, such as air or water, attenuation due to viscosity is negligible.
When sound is moving through a medium that does not have constant physical properties, it may be refracted (either dispersed or focused).[2]

STATIONARY WAVES

STATIONARY WAVES
In physics, a standing wave – also known as a stationary wave – is a wave that remains in a constant position.
Two opposing waves combine to form a standing wave.
This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling in opposite directions. In the second case, for waves of equal amplitude traveling in opposing directions, there is on average no net propagation of energy.
In a resonator, standing waves occur during the phenomenon known as resonance.

RIFFLE TANK

RIFFLE TANK:-
In physics and engineering, a ripple tank is a shallow glass tank of water used in schools and colleges to demonstrate the basic properties of waves. It is a specialized form of a wave tank. The ripple tank is usually illuminated from above, so that the light shines through the water. Some small ripple tanks fit onto the top of an overhead projector, i.e. they are illuminated from below. The ripples on the water show up as shadows on the screen underneath the tank. All the basic properties of waves, including reflection, refraction, interference and diffraction, can be demonstrated.
Ripples may be generated by a piece of wood that is suspended above the tank on elastic bands so that it is just touching the surface. Screwed to wood is a motor that has an off centre weight attached to the axle. As the axle rotates the motor wobbles, shaking the wood and generating ripples.

TRASVERSE WAVES

 Transverse wave is a moving wave that consists of oscillations occurring perpendicular (or right angled) to the direction of energy transfer. If a transverse wave is moving in the positive x-direction, its oscillations are in up and down directions that lie in the y–z plane. Light is an example of a transverse wave. For transverse waves in matter the displacement of the medium is perpendicular to the direction of propagation of the wave. A ripple on a pond and a wave on a string are easily visualized transverse waves.

SIMPLE PENDULUM

A pendulum is a weight suspended from a pivot so that it can swing freely.[1] When a pendulum is displaced sideways from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force combined with the pendulum's mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. A pendulum swings with a specific period which depends (mainly) on its length.
From its discovery around 1602 by Galileo Galilei the regular motion of pendulums was used for timekeeping, and was the world's most accurate timekeeping technology until the 1930s.[2] Pendulums are used to regulate pendulum clocks, and are used in scientific instruments such as accelerometers and seismometers. Historically they were used as gravimeters to measure the acceleration of gravity in geophysical surveys, and even as a standard of length. The word 'pendulum' is new Latin, from the Latin pendulus, meaning 'hanging'.[3]
The simple gravity pendulum[4] is an idealized mathematical model of a pendulum.[5][6][7] This is a weight (or bob) on the end of a massless cord suspended from a pivot, without friction. When given an initial push, it will swing back and forth at a constant amplitude. Real pendulums are subject to friction and air drag, so the amplitude of their swings declines.

Simple Harmonic Motion

IT IS ONE OFTHE MOST IMPORTANT TOPIC OF PHYSICS.Simple harmonic motion is typified by the motion of a mass on a spring when it is subject to the linear elastic restoring force given by Hooke's Law. The motion is sinusoidal in time and demonstrates a single resonant frequency.

Motion equations Motion calculation Frequency calculation Motion sequence visualization
Damped oscillation Driven oscillation


 







Simple Harmonic Motion Equations

The motion equation for simple harmonic motion contains a complete description of the motion, and other parameters of the motion can be calculated from it.
The velocity and acceleration are given by
The total energy for an undamped oscillator is the sum of its kinetic energy and potential energy, which is constant at
Energy transformation in periodic motion








Simple Harmonic Motion Calculation

The motion equations for simple harmonic motion provide for calculating any parameter of the motion if the others are known.


If the period is T =s
then the frequency is f = Hz and the angular frequency = rad/s.
The motion is described by
Displacement = Amplitude x sin (angular frequency x time)
y
=
A
x sin (
ω
x
t
)
m
=
m
x sin (
rad/s
x
s
)
Any of the parameters in the motion equation can be calculated by clicking on the active word in the motion relationship above. Default values will be entered for any missing data, but those values may be changed and the calculation repeated. The angular frequency calculation assumes that the motion is in its first period and therefore calculates the smallest value of angular frequency which will match the other parameters. The time calculation calculates the first time the motion reaches the specified displacement, i.e., the time during the first period.