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TYPES OF ISOMERISM

2008-04-18T23:17:00.000-07:00

The existence of two or more compounds with same molecular formula but different properties (physical, chemical or both) is known as isomerism; and the compounds themselves are called isomers..........

i) Chain, nuclear or skeleton isomerism:

This type of isomerism is due to the difference in the nature of the carbon chain (i.e. straight or branched) which forms the nucleus of the molecule,

ii) Position isomerism:

It is due to the difference in the position of the substituent atom or group or an unsaturated linkage in the same carbon chain.

iii) Functional isomerism:

This type of isomerism is due to difference in the nature of functional group present in the isomers,

iv) Metamerism:

It is due to the difference in nature of alkyl groups attached to the same functional group. This type of isomerism is shown by compounds of the same homologous series.

v) Tautomerism:

Tautomerism may be defined as the phenomenon in which a single compound exists in two readily interconvertible structures that differ markedly in the relative position of at least one atomic nucleus, generally hydrogen. The two different structures are known as tautomers of each other.

Stereo isomerism:

When isomers have the same structural formula but differ in relative arrangement of atoms or groups in space within the molecule, these are known as stereoisomers and the phenomenon as stereoisomerism. The spatial arrangement of atoms or groups is also referred to as configuration of the molecule and thus we can say that the stereoisomers have the same structural formula but different configuration. Stereoisomerism is of two types.

(i) Geometrical isomerism:

The isomers which possess the same structural formula but differ in the spatial arrangement of the groups around the double bond are known as geometrical isomers and the phenomenon is known as geometrical isomerism.

ii) Optical isomerism:

This type of isomerism arises from different arrangements of atoms or groups in three dimensional space resulting in two isomers which are mirror image of each other. Optical isomers contain an asymmetric (chiral) carbon atom ( a carbon atom attached to four different atoms or groups) in their molecules.

WORK

2008-04-18T23:00:00.000-07:00

all in one formulae

2008-02-20T20:23:00.000-08:00

magnetism concept collection…………….

2008-02-20T10:02:00.000-08:00

André-Marie Ampére is credited with the discovery of
electromagnetism, the relationship between electric
currents and magnetic fields.
Heinrich Hertz was the first to generate and detect
electromagnetic waves in the laboratory.
Magnetic Force acting on a charge q: [Newtons N]
F = qvBsinq
F = qv ´ B
F = force [N]
q = charge [C]
v = velocity [m/s]
B = magnetic field [T]
q = angle between v and B
Force on a Wire in a Magnetic Field: [Newtons N]
F = BI lsinq
F = I l ´ B
F = force [N]
B = magnetic field [T]
I = amperage [A]
l = length [m]
q = angle between B and the
direction of the current
Torque on a Rectangular Loop: [Newton·meters N·m]
t = NBIAsinq N = number of turns
B = magnetic field [T]
I = amperage [A]
A = area [m2]
q = angle between B and the plane of loop
Charged Particle in a Magnetic Field:
r=mv/qB
r = radius of rotational path
m = mass [kg]
v = velocity [m/s]
q = charge [C]
B = magnetic field [T]
Magnetic Field Around a Wire: [T]
B=₀ I/2r
B = magnetic field [T]
₀ = the permeability of free space 4pi×10-7 T·m/A
I = current [A]
r = distance from the center of the conductor
Magnetic Field at the center of an Arc: [T]
B=₀I /4 pi r

B = magnetic field [T]
₀= the permeability of free space 4p×10-7 T·m/A
i = current [A]
= the arc in radians
r = distance from the center of the conductor
Hall Effect: Voltage across the width of a
conducting ribbon due to a Magnetic Field:
(ne)V h =Bi
vd Bw =V w
ne = carrier charge density [C/m3]
Vw = voltage across the width [V]
h = thickness of the conductor [m]
B = magnetic field [T]
i = current [A]
vd = drift velocity [m/s]
w = width [m]
Force Between Two Conductors: The force is
attractive if the currents are in the same direction.

F = force [N]
l = length [m]
₀ = the permeability of free space 4p×10-7 T·m/A
I = current [A]
d = distance center to center [m]
Magnetic Field Inside of a Solenoid: [Teslas T]
B = ₀nI
B = magnetic field [T]
₀ = the permeability of free space 4p×10-7 T·m/A
n = number of turns of wire per unit length [#/m]
I = current [A]
Magnetic Dipole Moment: [J/T]
= NIA
= the magnetic dipole moment [J/T]
N = number of turns of wire
i = current [A]
A = area [m2]
Magnetic Flux through a closed loop: [T·M2 or Webers]
= BAcos

B = magnetic field [T]
A = area of loop [m2]
= angle between B and the perpendicular to the plane of
the loop plane of the loop

misconceptions in electricity…………

2008-02-20T09:51:00.000-08:00

1. All electric currents are flows of electrons? Wrong.

Electric currents are not just flows of electrons, they are flows of electric charge. Both protons and electrons posses exactly the same amount of ‘electricity.’ If either the protons *OR* the electrons flow, that flow is an electric current. In salt water, in fluorescent bulbs, and in battery acid, atoms with extra protons can flow along, and this flow is a genuine electric current. And in fuel cell membranes and in solid ice, electric current is actually a flow of protons.

2. “Electricity” is made of electrons, not protons? Nope.

Charges of “electricity” are carried both by electrons and protons. These two types of particles have very different weights (mass), but both have exactly the same amount of charge. Electrons are easily removed from atoms, while protons USUALLY are stuck to other protons, but that doesn’t affect the amount of charge they carry. If we remove an electron from an atom, that atom is left with too many protons, and that’s the only reason why the atom has an excess of positive electric charge. ALL positive charges in objects and in circuits are created by protons.

3. Electrons are a kind of energy particle? Wrong.

Electrons and protons are matter, not energy. A flow of electrons is NOT a flow of energy, it is a flow of matter and of electric charge. Same goes for protons. And if you have a certain amount of charge in one place, you’ll have no clue about the amount of energy present. Coulombs are not Joules, and knowing the amount charge does not tell you the amount of energy you have. A moving electron does not carry energy along, any more than a moving air molecule carries a sound wave with it.

4. “Electricity” carries zero mass because electrons have little mass? No.

“Electricity” (meaning charge) has weight because charge is part of matter particles. A flow of charge always requires a flow of carrier particles, so electric current must always carry mass with it. Electric current in a wire is not a flow of energy, it is a flow of matter. Ion currents in an electroplating bath are a flow of considerable amounts of matter: electric currents can transport material. However, in normal circuits we rarely notice the moving mass. There are two reasons for this: the flow is circular, so an electric current doesn’t need to build up mass anywhere. Secondly, the flow is very very slow, so even if the current were moving a huge amount of mass, we’d never notice this.

5. Positive charge is really just a loss of electrons? Wrong.

Positive charge is not made of “missing electrons.” Positive charge is a genuine type of charge in its own right. Yes, when protons and electrons are near each other, their charges cancel. Removing the electrons exposes the charge on the protons, and that’s probably where this particular misconception originates. Since neutral atoms receive an imbalance of positive charge when electrons are removed, is seems like positive charge is nothing but missing electrons. This is wrong. If you have a handful of protons, you have a handful of positive charge. A proton is not a missing electron. And if you have a vacuum, a total lack of electrons, that doesn’t mean that any positive charges are present.

6. Positive charge cannot flow? Totally wrong.

Current in a metal wire is a flow of electrons, but in many other conductors both the positive and negative charges can flow. For example, when you get a shock, no electrons flow through your body. The electric current inside your tissues is made of positively charged atoms flowing one way and negatively charged atoms flowing the other. The same is true of electrical currents in salt water, in the ground, and in battery electrolyte. When your car battery is supplying 300 amps to the starter motor, 300A worth of ions is flowing through the battery acid, and half of these are carrying positive charge. Also, plasmas can have positive ion currents as well as negative electron flows: examples are neon signs, fluorescent lights, camera flashes, and sparks of all kinds. There are even some conductors where the current is a flow of positive hydrogen ions, +H ions, otherwise known as protons. One common “proton conductor” is ice. Others are used as solid electrolytes in exotic batteries and, more recently are found as proton-conductor solid electrolyte membranes in tiny fuel cells.

7. To create “static” charge, we transfer the electrons? Not always.

“Static” or imbalanced charges can be created by removing electrons from a neutral atom. They can also be created by adding or removing charged atoms from an object, and the ions being removed can be negative or positive ions. It is even possible to add or remove bare protons from some materials (after all, protons are the same as H+ positively charged hydrogen atoms.) If you have some positively-charged water, or ice, or acid, then you probably have too many bare protons (too many H+ ions.)