Messages posted by vichu_487

THey are solids where there is only a small difference in energy called band gap,between the filled valency band of electrons and a conduction band.The conductivity is in between that of a metal and an insulator and depends on the no. of electrons in conduction band .

MOST important semi conductors widely used is silicon and germanium.Atoms of Si and Ge have 4 elns in their outer shell which can form 4 covalent bonds to other atoms.

Pure Si and Ge can be made semiconducting in controlled way by adding impurities which acts as charge carriers..Some atoms which have 5 electrons like Arsenic are deliberately added to silicon .This is called DOPPING .A minute portion of Si is replaced by As atom with 5 electns.only 4 of 5 is required to form bonds in lattice. THis extra electron can carry current.THis type of semiconductors is called n-type......NEGETIVE type

the other type is p-type or POsitive type.where the Si is dopped with atoms of 3 outer electrons like Indium.It uses its 3 outer electrons to form 3 bonds in the lattice, but one bond is incomplete .This site is called positive hole.The positive hole can migrate across the crystal conducting electricity

Generally Arsenic and Indium are used as dopping materials becoz of thier low melting points

Refer problem 1.129

Wen 2 springs of spring constant K1 and K2 when connected together How does the resultant become

K1K2 / (K!+K2) plz help me!!!!!!!

ANd another doubt ..........

There is a spring connected to wall stiffness k

Wen i exert a force F to extend it x metres without imaprting any KE to it.

the equation for its motion is

F- kx = ma where a is some acceleration

OR That Forece F-Kx=0

DOES it Accelerate or NOT????????

I have doubt

i think it decelerates ... as wen u apply EnerGy conseravtion we find that

F=half kx ...............HOw do we find that deceleation using newtoons law????????

no ..........Here the spehear is accelerating..... i want it from ground frame]

WHen a body is placed on a sphere ( R radius) moving with W acceleration (horizontal)The body is sliding.We need to find the velocity at time of break oofff .......then the equation for energy conservation be.change in ...

potentil to kinetic ...........but it is given in th bokk like the following plz help

1/2mv^2 (K.E) +mWRsin

=mg(R-Rcos

)( P.E)

Whyhas he put mWRsin teeta ???????? plzzz help me

plz help me!!!!!11

plz give the full answer....with .. reason

When a car is moving in circle without any tangential acceleration.....constant velocity

When it is moving in a crircle with constant tangential accelration ........ starting from rest

.............just give the formula............

How to learn what easier?????? oh organic chemistry???? IF you want to strengthen your organic chemistty first you remember that chemistry is not subject of crammin.PLZ DONT MUG UP this only based on mechanism of reaction so you must first improve your mechanism of reaction .also properly work on reagents and there working.be good in nomenclature, CHEMISTRY STANDS FOR TRUTH so understand and interpreteit

RATE ME!!!!!!!!!!!

a table with smooth horizontal surface fixed in cabin rotates with angular velocity

in a circular path of radius R.A smooth groove AB of length L(<<R) the groove makes an angle teeta with radius OA of circle in which cabin rotates.A small particle is kept at point A in the grrovve and released to move along AB .Fin d the time it takes to reach B.......

PLZ help..............

HEy u need to have the diagram..................I donno how to draw in commp

the entire question is diagram......... so plz refer page 115 .....22 i want the full solution............plz help.............

COOL MAN!!!!!!!!!

The ultimate, good ,tough, cheap,small .... BOOK

a small mass m kept at the left end of a larger block of mass M and length L .the system can slide on a horizontal road ,The system is started twards right with initial velocity v.The frriction coefficient between the road the bigger block is

and betwween the blocks is

/2 Find the time elapsed before the sammler block seperates from the biggerblock...GIVE THE FULL SOLUTION

Without use of pseudo force u can solve all the problem of newtons law........its just a mathematical triick to solve it more quickly and easily......but u will make mistakes if u are not clear of using it......my advise is better dont use it.........

the last problem in hc verma.......a block is kept on thefloor of elevator atrest the elevator is descending with 12 m/s2 then find the displacement in 0.2secs

the ans is 20cm...........

first it is on floor so normail reaction N is up...... later after a while its decening with 12its N is down.......so the answer will be the diplacement in which it was decelearting with g from floor to celing......so g = a and time interval for which he asked is 0.2...apllying we get it 20 cm....but my question is whether this interpreation correct?????????

I think it is b a c the decresing order.......as secod one it is allylic alpha carbon not sure .............

sp is more electro negetive than sp2 which more elctro- ve than sp3

So the option is b) sp3 and sp only

FROM LEFT
1st- sp3 terathydral 109 d 28'
2nd-sp linear 180 d
3rd-sp linear 180 d
4th -sp3 terathydral 109 d 28'

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