A heated object (at time t = 0 and temperature T=T_(0) ) is taken out of the oven to cool and placed on a table near an open window. Write an depression for its temperature as a function of time T, where T_(S) is the surrounding temperature

Two person A , B in order cut a pack of cards replacing them after each out. The person who first cuts a club shall prize. The probabilities of their winning are

Read the following passage and answer the questions at the end of it. Conductivity of silicon increases if it is doped with certain other elements. Doping means introduction of small amount of impurities like phosphorus, arsenic or boron in the pure crystal. In pure silicon four valencies are used in bonding with other four adjacent silicon atoms. When a silicon crystal is doped with a group - 15 element (with five valence electrons) such as P, AsSb or Bi, the structure of the crystal lattice remains unchanged. Out of the five valence electrons of group - 15 doped element, four electrons are used in normal covalent bonding with silicon and fifth electron is delocalised and thus conducts electricity Doping a silicon crystal with a group-13 element (with three valence electron) such as B, Al, Ga or In produces a semiconductor with three electrons in dopant. The place where fourth electron is missing is called as electron vacancy or hole. Silicon that has been doped with group - 15 elements is called