PCM Student

Adding Carbon atoms to an organic compound

noreply@blogger.com (Mradul Verma) — Thu, 07 Mar 2013 13:52:00 +0000

Stepping up Series | conversion Concept Map

Well, sometimes adding carbon atoms to an organic compound or what we call stepping up the series can be pretty mind boggling for some students so here’s something for them.

Just see the concept map below and you will be able to add carbon atoms in all sort of organic compounds and will never find problem in stepping up the series.

Chemistry in Everyday Life Theory | Notes

noreply@blogger.com (Mradul Verma) — Tue, 05 Mar 2013 15:24:00 +0000

DRUGS

Drugs are chemical of low molecular masses, which interact with macro-molecular targets and produce a biological response.

CHEMOTHERAPY
The use of chemicals for therapeutic effect is called chemotherapy.

CLASSIFICATION OF DRUGS

ON THE BASIS OF PHARMACOLOGICAL EFFECT
Drugs for a particular type of problem eg. as analgesics-----for pain relieving.
ON THE BASIS OF DRUG ACTION
Action of drug on a particular biochemical process.
ON THE BASIS OF CHEMICAL ACTION
Drugs having similar structure .eg- sulpha drugs.
ON THE BASIS OF MOLECULAR TARGETS
Drugs interacting with bio molecules as lipids, proteins.

ENZYMES AS DRUG TARGETS

CATALYTIC ACTION OF ENZYMES

Enzymes have active sites which hold the substrate molecule .it can be attracted by reacting molecules.
Substrate is bonded to active sites through hydrogen bonds, ionic bonds, Van der Waal or dipole –dipole interactions.

DRUG- ENZYME INTERACTIONS

Drug enzyme interaction

Drug compete with natural substrate for their attachments on the active sites of enzymes .They are called competitive inhibitors.
Some drugs binds to a different site of the enzyme called allosteric sites which changes the shape of active sites.

ANTAGONISTS
The drugs that bind to the receptor site and inhibit its natural function.
AGONISTS
Drugs mimic the natural messenger by switching on the receptor.
ANTACIDS
These are compounds which neutralize excess acid of stomach.eg-Aluminium hydroxide, Magnesium hydroxide.
ANTI HISTAMINES
The drugs which interfere with the natural action of histamines and prevent the allergic reaction. eg- ranitidine, tegamet, avil.
TRANQULIZERS
The class of chemical compounds used for the treatment of stress, mild or even severe mental diseases. Eg- luminal, seconal, equanil, idardil, iproniazid.
ANALGESICS
They reduce pain without causing impairment of consciousness, mental confusion or some other disturbance of the nervous system. Eg - aspirin, seridon, phenacetin.

ANTIMICROBIALS

They tend to prevent/destroy or inhibit the pathogenic action of microbes as bacteria ,virus ,fungi etc. They are classified as

ANTIBIOTICS
Those are the chemicals substances which are produced by micro-organisms and use to kill the pathogenic micro-organism. Eg- Penicillin , ofloxacin .

NARROW SPECTRUM ANTI-BIOTICS

These are effective mainly against gram positive or gram negative bacteria. Eg- Penicillin , streptomycin.
BROAD SPECTRUM ANTI-BIOTICS
They kill or inhibit a wide range of micro-organisms.
eg- chloramphenicol , tetracycline .

ANTISEPTICS OR DISINFECTANT
These are which either kill/inhibit the growth of micro-organisms. Antiseptics are applied to the living tissues such as wounds, cuts, ulcers etc. eg- furacine, chloroxylenol & terpinol (Dettol) .Disinfectant are applied to inanimate objects such as floors , drainage , system. Eg- 0.2% solution of phenol is an antiseptic while 1% solution is disinfectant.

ANTIFERTILITY DRUGS
These is the chemical substances used to control the pregnancy. They are also called oral contraceptives or birth control pills. Eg-Mifepristone, norethindrone.

ARTIFICIAL SWEETNING AGENTS
These are the chemical compounds which give sweetening effect to the food without adding calorie. They are good for diabetic people e.g.- aspartame, saccharin, alitame , sucrolose.
FOOD PRESERVATIVES
-They prevents spoilage of food to microbial growth.eg-salt, sugar, and sodium benzoate.

CLEANSING AGENTS

SOAPS

They are sodium or potassium salts of long chain fatty acids. They are obtained by the saponification reaction, when fatty acids are heated with aqueous sodium hydroxide.

They do not work well in hard water.

TOILET SOAP
This is prepared by using better grade of fatty acids and excess of alkali needs to be removed. colour & perfumes are added to make them attractive.
MEDICATED SOAPS
Substances of medicinal value are added.eg- Bithional, Dettol.

SYNTHETIC DETERGENTS

They are cleaning agents having properties of soaps, but actually contain no soap .They can used in both soft and hard water .They are

ANIONIC DETERGENTS
They are sodium salts of sulphonated long chain alcohols or hydrocarbons.eg-sodium lauryl sulphonate. They are effective in acidic solution.
CH3(CH2) CH2OH → CH3 (CH2)10CH2OSO3H→CH3 (CH2)10CH2SO3-Na+
(laurylalchol) (Sodium lauryl sulphonate)
CATIONIC DETERGENTS

They are quaternary ammonium salts of amines with acetates , chlorides, or bromides.They are expensive used to limited extent.eg- cetyltrimethylammoniumbromide

NON-IONIC DETERGENTS

They does not contain any ions. Some liquid dishwashing detergents which are of non-ionic type.

BIODEGREDABLE DETERGENTS
The detergents which are linear and can be attacked by micro-organisms are biodegradable.
Eg -sodium 4-(1-dodecyl) benzene sulphonate.

NON-BIODEGREDABLE DETERGENTS
The detergents which are branched and cannot be decomposed by micro-organisms are called non-biodegradable.eg-sodium 4-(1,3,5,7 tetramethyloctl)-benzene sulphonate .It creates water pollution.

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Semiconductor and Electronic Devices Theory | Notes

noreply@blogger.com (Mradul Verma) — Sat, 02 Mar 2013 03:59:00 +0000

Energy band diagrams

In metals, the conduction band and valence band partly overlap each other and there is no forbidden energy gap or there is partially filled conduction band.

Energy band diagram of metals

In insulators, the conduction band is empty and valence band is completely filled and forbidden gap is quite large ~ 6 eV. No electron from valence band can cross over to conduction band at room temperature, even if electric field is applied. Hence there is no conductivity of the insulators.

Energy band diagram of insulators

In semiconductors, the conduction band is empty and valence band is totally filled. But the forbidden gap between conduction band and valence band is quite small, which is about 1 eV. No electron from valence band can cross over to conduction band. Therefore, the semiconductor behaves as insulator. At room temperature, some electrons in the valence band acquire thermal energy, greater than energy gap of 1 eV and jump over to the conduction band where they are free to move under the influence of even a small electric field. Due to which, the semiconductor acquires small conductivity at room temperature

Energy band diagram of semiconductors

Differences

	Distinction between Intrinsic and Extrinsic Semiconductor
Intrinsic		Extrinsic
1	It is pure semiconducting material and no impurity atoms are added to it	1	It is prepared by doping a small quantity of impurity atoms to the pure semiconducting material.
2	Examples are crystalline forms of pure silicon and germanium.	2	Examples are silicon and germanium crystals with impurity atoms of arsenic, antimony, phosphorous etc. or indium, boron, aluminum etc.
3	The number of free electron in conduction band and the number of holes in valence band is exactly equal and very small indeed.	3	The number of free electrons and holes is never equal. There is excess of electrons in n-type semiconductors and excess of holes in p-type semiconductors.
4	Its electrical conductivity is low	4	Its electrical conductivity is high.
5	Its electrical conductivity is a function of temperature alone.	5	Its electrical conductivity depends upon the temperature as well as on the quantity of impurity atoms doped in the structure.

Distinction between n-type and p-type semiconductors
n-type semiconductors				p-type semiconductors
1	It is an extrinsic semiconductors which is obtained by doping the impurity atoms of Vth group of periodic table to the pure germanium or silicon semiconductor.	1	It is an intrinsic semiconductors which is obtained by doping the impurity atoms of III group of periodic table to the pure germanium or silicon semiconductor.
2	The impurity atoms added, provide extra electrons in the structure, and are called donor atoms.	2	The impurity atoms added, create vacancies of electrons (i.e. holes) in the structure and are called acceptor atoms.
3	The electrons are majority carriers and holes are minority carriers.	3	The holes are majority carriers and electrons are minority carriers.
4	The electron density (n_e) is much greater than the hole density (n_h)i.e. n_e>>(n_h)	4	The hole density (n_e) is much greater than the electron density (n_h)i.e. n_h>> n_e
5	The donor energy level is close to the conduction band and far away from valence band.	5	The acceptor energy level is close to valence band and is far away from the conduction band.
6	The Fermi energy level lies in between the donor energy level and conduction band.	6	The Fermi energy level lies in between the acceptor energy level and valence band.

P-n junction diode

Two important processes occur during the formation of p-n junction, diffusion and drift.
The motion of majority charge carriers give rise to diffusion current.
Due to the positive space charge on n-side junction and negative space charge region on p-side the electric field is set up and potential barrier develops at the junction Due to electric field electrons on p-side moves to n and holes from n-side to p-side which is called drift current.
In equilibrium state, there is no current across p-n junction and potential barrier across p-n junction has maximum value .
The width of the depletion region and magnitude of barrier potential depends on the nature of semiconductor and doping concentration on two sides of p-n junction –

Forward Bias

P-n junction is forward biased when p-type is connected to the positive terminal of battery and n-type connected to negative terminal of battery.
Potential barrier height is reduced and width of depletion layer decreases.
Resistance of p-n junction is low to the flow of current in this condition.

Reverse Bias

P-n junction is reverse biased when p-type connected to the negative terminal of battery and n-type connected to positive terminal of battery.
Resistance of p-n junction is high to the flow of current in this condition.
Potential barrier height is increased and width of depletion layer increases

Diode Characteristics:

Diode Characteristics circuit diagram under forward bias

Diode Characteristics circuit diagram under reverse bias

Diode Characteristics graph under reverse bias

Diode Characteristics graph under forward bias

Rectification

p-n junction diode as half wave rectifier

p-n junction diode as full wave rectifier

Zener diode as a voltage regulator

Photonic(Optoelectronic) Devices

LED

PHOTODIODE

SOLARCELL

Symbol of LED

Forward biased

Symbol of Photodiode

Reverse biased

Symbol of Solar Cell

No external baising,It generates emf when solar radiation falls on it.

Recombination of electrons and holes take place at the junction and emits electromagnetic radiations

Energy is supplied by light to take an electron from valence band to conduction band.

Generation of emf by solar cells is due to three basic process generation of electron-hole pair,separation and collection

It is used in Burglar alarm, remote control

LED Characteristics graph

It is used in photo detectors in communication

Photodiode Characteristics graph

It is used in satellites,space vechicles calculators.

Solar Cell Characteristics graph

Transistor

npn transistor and pnp transistor

• There are two types of transistor – NPN & PNP

• Applications of transistor

Transistor as a switch
Transistor as an amplifier
Transistor as an oscillator

Transistor- Switch

When a transistor is used in cut off or saturated state, it behaves as a switch.

Transistor as switch, Cutoff region, Active Region, Saturation Region

Transistor as an Amplifier

Current gain, Voltage gain and Power gain

An amplifier is a device which is used for increasing the amplitude of variation of alternating voltage or current or power,thus it produces an enlarged version of the input signal.

For Circuit diagram refer Ncert diagram

Transistor-Oscillator-

• In an oscillator, we get ac output without any external input signal. In other words, the output in an oscillator is self- sustained. Oscillator converts D.C into A.C

Digital Electronics –Logic Gates

• The three basic Logic Gates are

(1) OR Gate

OR gate, AND gate & NOT gate

OUTPUT Y= A + B

(2) AND Gate

OUTPUT Y=A.B

(3) NOT GATE

OUTPUT Y=Y’

COMBINATION OF GATES

(1) NOR GATE--OUT PUT Y = A+B

(2) NAND GATE--OUT PUT Y= A .B

Communication Systems Theory | Notes

noreply@blogger.com (Mradul Verma) — Fri, 01 Mar 2013 11:27:00 +0000

Communication Systems

COMMUNICATION

The sending and receiving of message from one place to another is called communication. Two important forms of communication systems are :

(i) Analog and

(ii) digital.

In analog communication the signal is continuous while in digital communicationthe signal is discrete.

THREE BASIC ELEMENTS OF COMMUNICATION

(i) Transmitter (ii) Communication channel (iii) Receiver

MODULATION

The superposition of low frequency message signal over high frequency carrier wave is called modulation.

NEED FOR MODULATION:

* Size of antenna h= λ/4 so, for low frequency. Height will be large which is impossible.

* Effective power radiated by an antenna Power proportional to 1/(wavelength)2

* Mixing up of signals from different transmitters.

TYPES OF MODULATION

There are two broad types of modulation:

(i) Continuous wave modulation

(ii) Pulse modulation.

1. Continuous wave modulation is of three types:

(i) Amplitude modulation (AM): In amplitude modulation, the amplitude of carrier wave varies in accordance with instantaneous voltage of information (or message) signal.

(ii) Frequency modulation (FM): In frequency modulation the frequency of carrier wave is varied in accordance with instantaneous voltage of information signal.

(ii) Phase modulation (PM): In phase modulation, the phase of carrier wave is varied in accordance with the information signal.

Amplitude modulation

SPACE COMMUNICATION

Space communication uses free space between transmitter and receiver.

Space communication is via:

(i) ground waves (ii) space waves (iii) sky waves

GROUND OR SURFACE WAVE PROPAGATION is a mode of wave propagation in which the ground has a strong influence on the propagation of signal wave from the transmitting antenna to receiving antenna .In this propagation ,the signal waves glides over the surface of earth, Ground waves are heavily absorbed by earth and not suitable for long range communication. Ground wave propagation can be sustained only at low frequencies (500 kHz-1500 kHz).

SKY WAVE PROPAGATION is a mode of wave propagation in which the radio wave emitted from the transmitter antenna reach the receiving antenna after reflection by ionosphere. Sky wave propagation is possible because of reflection of carrier signals from ionosphere or satellite.

SPACE WAVE PROPAGATION higher than 30 MHz is that mode of wave propagation in which the radio waves emitted from the transmitter antenna reach the receiving antenna through space. These radio waves are called space waves. It is also called line of sight communication. Space wave is suitable for UHF/VHF regions.

Band width of the signal

Type of signal	Band width
Speech	2800 Hz
Music	20 KHz
Video	42 MHz
Video & Audio (T.V)	6.0 MHz

COVERING RANGE OF T.V. TRANSMITTING TOWER is d=√2R_eh, where h is height of tower and R_eradius of earth. T.V. waves are frequency modulated waves. VHF T.V. waves range from 47 to 230 MHz and UHF T.V. waves have range from 470 to 960 MHz.

Maximum line of sight distance d_m =√2Rh_T + √2Rh_R.

MAXIMUM USABLE FREQUENCY

It is that highest frequency of radio waves which when sent at some angle towards the ionosphere, gets reflected from that and returns to the earth.

SATELLITE COMMUNICATION

The communication satellite is used for reflecting sky waves without any disturbance. Its height is 35800 km above earth’s surface. To cover entire globe of earth simultaneously 3-satellites are employed.

IMPORTANT FORMULAE

1. Marconi antenna is grounded, and its length = λ/4,where λ is wavelength of the waves transmitted. It is called quarter wave antenna.

2. Hertz antenna is not grounded, and its length = λ/2. It is called half wave antenna.

3. Side band frequencies in AM wave are υ_SB= υ_{c ±}υ_mwhere υ_mis frequency of modulating (audio) signal.

4. Modulation index, m_a = E_m/ E_c

Modulation index, m_a= E_max – E_min / E_max+ E_min

6. Coverage range (d) for a given height (h) of antenna

d = √2hR where R = radius of earth.

d = √2Rh_r+ √2Rh_R,where h_T, h_R are the heights of transmitter and receiver antennas.

7. Population covered = population density x area covered.

8. Number of channels,

N = Total band width of channels / Band width per channel

Communication System – Block Diagrams

PCM Student

Adding Carbon atoms to an organic compound

Stepping up Series | conversion Concept Map

Chemistry in Everyday Life Theory | Notes

DRUGS

CHEMOTHERAPY

CLASSIFICATION OF DRUGS

ON THE BASIS OF PHARMACOLOGICAL EFFECT

ON THE BASIS OF DRUG ACTION

ON THE BASIS OF CHEMICAL ACTION

ON THE BASIS OF MOLECULAR TARGETS

ENZYMES AS DRUG TARGETS

CATALYTIC ACTION OF ENZYMES

DRUG- ENZYME INTERACTIONS

ANTAGONISTS

AGONISTS

ANTACIDS

ANTI HISTAMINES

TRANQULIZERS

ANALGESICS

ANTIMICROBIALS

ANTIBIOTICS

NARROW SPECTRUM ANTI-BIOTICS

ANTISEPTICS OR DISINFECTANT

ANTIFERTILITY DRUGS

ARTIFICIAL SWEETNING AGENTS

FOOD PRESERVATIVES

CLEANSING AGENTS

SOAPS

TOILET SOAP

MEDICATED SOAPS

SYNTHETIC DETERGENTS

ANIONIC DETERGENTS

NON-IONIC DETERGENTS

BIODEGREDABLE DETERGENTS

NON-BIODEGREDABLE DETERGENTS

Semiconductor and Electronic Devices Theory | Notes

Related articles

Communication Systems Theory | Notes