Messages posted by Jyothi

thanx u all.............

hi Jaysun ,

we will not be shocked by touching a high voltage if there is no path for the current to reach the earth or a different voltage point. if u touch a 120 volt circuit with one hand, u can escape serious shock if u hav insulating shoes which prevent a low-resistance path to ground. electricity requires a complete path (circuit) to continuously flow.so without two contact points on the body for current to enter and exit, there is no hazard of shock.

insulated shoes and mats are made to protect persons frm shock , but even these pieces of gear must be in clean, dry condition to be effective. Normal footwear is not gud enough to provide protection frm shock by insulating its wearer frm the earth.

hope its clear now

gr88888888 post........................Himanshu..................gud work

CONGRATS..............

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U shld conduct urself in such a manner that everyone loves u .u must keep ur mind peaceful.dont be distress if somebody criticise u .be large hearted nd pardon thm.whn u pardon thm,u hav relieved of a lot of burden.speak abt ur happiness nd pleasures with others.let thm notice tht there is some special aspect in u .

look at everything positively.nobody is bad or useless by birth.even a clock that has stopped working shows the correct time twice a day.concentrate on studies.ur sole aim in life shld be to study hard nd work wonders.spend ur time in improving urself.

Have firm faith in God,experience the presence of God in everyday life.hav a personal relationship with God.God will change ur life(as he did mine

).

God bless u....

All the best

http://en.wikipedia.org/wiki/Refrigeration

When the human body comes in direct contact with a source of electricity, the current passes through it, producing an electric shock.

lighting is one one the main reason for this.whn lightning occurs the high electric field cause an electric breakdown of the air,the intervening air gets ionized nd conducts charge frm the cloud to earth in the form of a lightning flash,nd deposits charge on earth...after each lightning flash, cloud bcms charged again nd is ready for the next flash.

We get electric shock whn we provide an easy path for the lightning to pass thrgh our body.whn we wear chappals,the discharge due to lightining is not conducted to the ground nd therefore we are safer.one of the safest way to protect ourself frm lightning is to be inside a car, the metallic body of the car provides electrostatic shielding to the person in the car,becoz electric field inside the car is zero.the discharging due to lightning passes thrgh the metallic body of the car.lightning conductors are used to save big buildings frm the damage.if the discharge of the cloud occurs,it passes thrgh the conducting copper strip nd the building is saved frm the damage.

thanx for comments

thanx for the comments

ho sry ...........
thanx chirag ..........

Important Chemical Terms - 2

ATOMIC STRUCTURE

· HUND?S RULE: when several orbital of the same type are available, the electrons 1^st fill at the orbitals of same energy singly with parallel spins b4 pairing in any orbital takes place.

· INFRARED RADIATION: electromagnetic radiations possessing wavelength b/w those of visible light nd those of radio waves, i.e;frm approximately 10^-4to 7x10^-7 m

· ISOTOPES: atoms having the same nuclear charge, but different numbers of neutrons in their nuclei.

· MAGNETIC QUANTUM NO: denotes the orbital an electron occupies within a sub shell.

· MASS NO: the sum of no of protons nd neutrons in the nucleus.

· MOLECULAR ORBIT: a polycentric region in space associated with two or more atoms in a molecule.

· NEUTRON: uncharged sub atomic particle having a mass of 1 amu

· NUCLEUS: the central +vely charged core of an atom tht contains practically all the mass.

· ORBITS: another name for the principle energy levels occupied by electrons in atoms.

· ORBITAL: region in space around the nucleus whr the probability of finding an electron is geatest. each orbital can hold a maxi. Of 2 electrons

· ORBITAL QUANTUM NO: same as azimuthal quantum no:

· PAULI EXCLUSION PRINCIPLE: as azimuthal quantum no:

· PARAMAGNETIC: the atom of a paramagnetic substance possesses permanent magnetic moment due to unbalanced electron spin.

· PHOTONS: light quanta (hv)

· PHOTOELECTRIC EFFECT: the phenomenon in which certain metal surfaces such as cesium, sodium,?,emit electrons, when electromagnetic radiations of sufficient energy are allowed to fall on them.

· PRINCIPLE QUANTUM NO: the no: used to designate the principle energy levels tht an electron may occupy I a n atom. it determines the energy level.

· PROBABILITY DISTRIBUTIONS OF ELECTRONS: the probability tht an electron with an atom will be at a certain point in space at a given time; determined by the magnitude of the square of the wave function.

· QUANTIZED: a quantity is said to be quantized, if in accordance with quantum mechanics, it can only have certain discrete values. Such a quantity cannot vary continuously, differences in value separated by jumps.

· QUANTUM: According to the quantum mechanics, energy exists in discrete units, only whole no: of which can exist. Each unit is called a quantum.

· QUANTUM MECHANICS: According to it, energy is quantized,i.e; emitted or absorbed in discrete units, the magnitude of which is given by the product of the frequency nd Planck?s constant.

· QUANTUM NUMBERS: An electron within an atom is specified by set of four numbers, called quantum number.

1) The principle quantum no: (n) defines the shell in which the electron occurs.

2) The azimuthal quantum no: (i) defines the shape of the orbit nd energy sub level.

3) The magnetic orbital quantum no: (m) determines the orientation of the orbit, with reference to a fixed direction

4) The spin quantum no: (s) distinguishes b/w the clockwise nd anticlockwise spin of an electron. this no: is either +/- ½

· RYDBERG?S CONSTANT: A constant relating to those atomic spectra which are similar to the hydrogen atom spectrum. for hydrogen, Rydberg constant is 109.737 cm^-1

· SPECTRAGRAPH: An instrument by which spectra may be photographed.

· SPECTRASCOPE: An instrument for spectrographic analysis or the observation of spectra.

· SPECTRUM: The result obtained when electromagnetic radiations are resolved into their constituent wavelengths or frequencies.

· THRESHOLD FREQUENCY: light incident on a metal will give rise to the emission of electrons only if the frequency of the light is greater than a certain threshold value, which is characteristics of the metal used.

· VOLT: A potential difference which applied across the ends of conductor having resistance of 1 ohm, causes a current of 1 ampere to flow.

· WAVE FUNCTION: in wave mechanics orbital electron is treated as three dimensional stationary wave system represented by a wave function the magnitude of which represents by the variation of amplitude of the wave system at various points around the nucleus.

· WAVE LENGTH: the distance b/w consecutive crests. it is equal to the velocity of the wave motion divided by its frequency.

· WAVE MECHANICS: According to it every particle is considered to be associated with a kind of periodic wave.

· WAVE MOTION: The propagation of a periodic disturbance carrying energy.

· WAVE NO: no of waves in unit length. reciprocal of wavelengths.

· X ? RAYS : Electromagnetic radiations of short wavelength of range 5x10 ^-7 cm to 6x 10^-10cm.

· ZEEMAN EFFECT: When a substance, which emits a line spectrum, is placed in a strong magnetic field, the single lines are split up into group of closely spaced lines

NOT COPY PASTED

Jyothi Susan George

1)

Important Chemical Terms - 1

Atomic Structure

A

ALPHA PARTICLE: A sub atomic particle tht has a mass of 4 unit?s nd a charge of +2. i.e.; a doubly charged helium ion (H²⁺)

2)

ANTIBONDING MOLECULAR ORBITAL: a molecular orbital formed by the subtraction of wave functions of the combining atomic orbitals.it destabilizes the molecule.

3)

ATOMIC MASS UNIT: unit used for expressing the masses of individual isotopes of elements, approximately equal to 1.66x 10^-24g

4)

ATOMIC NUMBER: the no of protons in the nucleus of an atom or no of electrons rotating around the nucleus of the neutrals atom

5)

ATOMIC MASS: the mass of an atom expressed in amu units.

6)

ATOMIC ORBITAL: region in space around the nucleus of a n atom, whr the probability of finding an electron is greatest. Each orbital can hold a maxi of 2 electrons.

7)

ATOMIC SPECTRUM: a group of characteristic pattern of lines in which each line represents a specific wave length of radiation, emitted by the atoms of an element.

8)

AUFBAU PRINCIPLE: electrons enter the various orbital to their respective capacities in increasing order of energy.

9)

AZIMUTHAL QUANTUM NO: denotes the sub shell tht an electron occupies nd specifies the shape of the electron cloud.

BALMER SERIES: Wave length ( ) of the series is given by:

1/

= R_N[1/2^{2_-1/n2_{],whr n}}₂>2

BETA PARTICLE: identical to electron in all respects

BOHR?S THEORY: according to Bohr?s theory:

1) The electrons in an atom are located in orbits or energy levels, around the nucleus.

2) The electrons in orbits closest to the nucleus are of lower energy than in orbits further away frm the nucleus.

3) Every electron in an atom may hav only certain allowed energies. This energy determines wht orbit the electron occupies.

4) The angular momentum of an allowed orbit of an atom is integral multiple of h/2

i.e.; m

r=nh/2

5) Electrons can move frm one orbit to another. To do this, an electron must gain or lose a certain exact amount of energy-a quantum of energy. Thus:

E₂-E_{1 =}E=h

BOHR?S THEORY OF HYDROGEN ATOM: wavelength of a spectral line in hydrogen atom is given by:

1/

= R_h[1/n_{1^{2 - 1/n2}}²]

14) BOND ENERGY: energy characterizing a chem. bond b/w two atoms, measured by the energy required to separate the two atoms.

BONDING MOLECULAR ORBITAL: an orbital formed as a result of addition of wave functions of atomic orbitals. It stabilizes the molecules.

16)

BOND LENGTH: the distance of the strength of the bond b/w the two atoms. Defined mathematically as

Bond Order= [no: of electrons in bonding molecular orbitals] - [no of electrons in antibonding molecular orbitals] / 2

17) COULOMB: a unit of electricity equal to ampere times second

18)

DE-BROGLIE CONCEPT: A wave can be a particle nd a particle can be a wave

19)

DE-BROGLIE REACTION: the wavelength (

) of a mass(m) moving with a velocity(v)is given by:

***

= h/m

20)

DUAL NATURE OF RADIATION: light has particle like nature nd each particle possesses wave characteristics also.

21)

ELECTROMAGNETIC RADIATION: a form of energy transmitted thrgh space without the apparent transmission of matter.

22)

ELECTRON: a subatomic particle having a charge -1 nd a mass of approximately 1/1840 of amu

23)

ELECTRON CLOUD: an orbital, the region in space around the nucleus, whr the probability of finding an electron is greatest.

24)

ELECTRON DIFFRACTION: the diffraction effect resulting frm the passage of electrons thrgh matter. This phenomenon provides evidence for the existence of wave associated with electrons.

25)

EMISSION SPECTRUM: the displayed wavelength distribution of light, coming frm an emitting substance.

26)

EXCITED STATE: an energy level of greater energy then the ground level

27)

EXTRA NUCLEAR PART: consists of electrons revolving around the nucleus in orbits.

28)

FREQUENCY: the no of vibrations per sec.

29)

GROUND STATE: the most stable energy state of an electron. i.e; the state in which electrons are in the lowest energy level available to them.

30)

HEISENBERG?S UNCERTAINTY PRINCIPLE: It is impossible to determine with accuracy both the position nd the momentum of a particle simultaneously. Thus:

***

x.m

> or =h

/4

Jyothi Susan George

thank u Smarty

superb.................thanx Himanshu :):).................

hehe..........good post .....Ankur

jyothiksg@gmail.com

good........

thanxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Himanshu........

gud............

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