Sunday, 19 February 2017

Tips and tricks for scoring marks in Jee mains

                                           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 .