Tuesday, 21 February 2017

Mathematics

Topic-1 Boolean expressions

Boolean expressions is one of the easiest topic and also important for scoring marks in competitive exams . If we check out the last three question papers of  mains examination we can find questions . Questions are as follows..

Jee mains 2016 paper question:-





         ANS(2) p /\ q

 

    p   q   ~p   ~q    p /\ ~q   ~p /\ q       ( p /\ ~q )  V q V (~p /\ q)      p /\ q
   
    1    0    0      1        1             0                            1                                     1

   
    1    1    0      0        0             0                            1                                     1
   

    0   0     1      1        0             0                            0                                     0


    0    1    1      0        0             1                            1                                     1



Jee mains 2015 paper question:-



        ANS(4)  

  s   r    ~s   ~r   ( ~r /\ s )   ~s V  ( ~r /\ s )    ~( ~s V  ( ~r /\ s ) )        s/\ r

  0   0     1     1          1                    1                               0                             0


  0   1     1    0          0                     1                               0                             0
 
  1   0     0    1         1                      1                               0                             0

  1   1     0    0         0                      0                               1                             1

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Sunday, 19 February 2017

                                           Physics 



Topic-1 Electronic devices

Electronic devices is a very important chapter since it is the base of today's technology . Marks wise also it's a very important chapter . If we check out in the last three years papers questions appeared from this chapter . The questions are as follows.


Jee mains 2016 paper questions:-



           ANS(3) Linear increase for cu , exponential decrease for si .



     Copper



   Intrinsic semi conductor 


  • Thus when temperature goes up, resistance goes up. For some materials, resistivity is a linear function of temperature . The resistivity of a conductor increases with temperature . In the case of copper, the relationship between resistivity and temperature is approximately linear over a wide range of temperatures.
  • So its conductivity increases. But in metal, it decreases due to the decrease in mobility. Conductivity of metal decrease with increase in temperature. For intrinsic semiconductor , conductivity increases with increase in temperature.



          ANS(3) OR




             a   b   c   d   x(output)   

0   0    0   0      0


0   0    0   1      1


0   0    1   0      1


0   0    1   1      1


0   1    0    0     1


0   1    0    1     1


1   0    1    0     1


1   0    1    1     1




  • By observing the table when at least one input is high (logic one)  the output is high (logic one) so the gate is OR .





















         ANS(2)  and (4)
  • By cross multiplying the below equations you can get the above relations





               ANS(1)


Jee mains 2014 paper questions:-




             ANS(1)
  •  Higher voltage should be connected to the anode of the diode and lower voltage should be connected to the cathode of the diode .




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Saturday, 18 February 2017

                                          Chemistry



Topic-2 Chemistry in everyday life

There is a high probability of getting question from this chapter ... If we check out the last three years papers of mains a question appeared in three years papers from this chapter . The questions are as follows..

Jeemains 2016 paper question:-



                              
         ANS(2) Sodium lauryl sulphate
  • All other options are cationic detergent .


Jeemains 2015 paper question:-



       ANS(3) Phenelzine
  • Phenelzine is a anti depressant drug .
  • All other options are antacid .


Jeemains 2014 paper question:-




       ANS(1) Quinoline
  • Quinoline is a aromatic compound and doesnot present in DNA .
  • All other options are bases and also present in DNA .

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Friday, 17 February 2017

Chemistry

   Topic-1 Polymers

There is a high probability of getting a question from this chapter . If we check out  the last three years papers a question appeared in all three years  from this chapter . The questions are as follows:-


Jeemains 2016  paper question:-



           ANS-(4) It is used in the manufacture of buckets , dustbins etc...

  •  It is is widely used for manufacturing various containers, dispensing bottles, wash bottles, tubing, plastic bags for computer components, and various molded laboratory equipment. Its most common use is in plastic bags

Jeemains 2015  paper question:-






            ANS-(2) Glyptal

  • BAKELITE used for its electrical non conductivity and heat-resistant properties in electrical insulators, radio and telephone casings and such diverse products as kitchenware, jewelry, pipe stems, children's toys, and firearms.


  • POLYPROPENE- is a thermoplastic polymer  used in a wide variety of applications including packaging and labeling, textiles (e.g., ropes, thermal underwear and carpets), stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive .

  • POLY VINYL CHLORIDE-Regular PVC (polyvinyl chloride) is a common, strong but lightweight plastic  used in construction. It is made softer and more flexible by the addition of plasticizers. If no plasticizers are added, it is known as uPVC (unplasticized polyvinyl chloride). Example PVC pipes , PVC cables etc..


Jeemains 2014 paper question:-




           ANS-(1) Dacron
  • Neoprene , Teflon and acrylonitrile are addition polymers.










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