Tag: properties of solids

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Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

Frenkel defect is observed in:

  1. $MgCl _2$
  2. $AgCl$
  3. $ZnS$
  4. $AgI$
Reveal answer Fill a bubble to check yourself
B,C,D Correct answer
Explanation

Frenkel defect is the defect which is created when an ion leaves its appropriate site in the lattice and occupies an interstitial site. A hole or vacancy is thus produced in the lattice.


Frenkel defect is exhibited in ionic compounds in which the radius ratio is low. The cations and anions differ much in their sizes and the ions have low co-ordination numbers. Examples are ZnS, AgBr, AgI, AgCl.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids
Assertion: The electrical conductivity of a semiconductor increases with increase in temperature.
Reason: With increase in temperature, large number of electrons from the valence band can jump to the conduction band.

  1. Both Assertion and Reason are correct and Reason is the correct explanation of Assertion

  2. Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion

  3. Assertion is correct but Reason is incorrect

  4. Assertion is incorrect but Reason is correct

  5. Both Assertion and Reason are incorrect
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
As temperature increases, some electrons are thermally released from the covalent bonds in pure Si or Ge. 
These electrons are free to move in the crystal and are responsible for electrical conductivity.
With an increase in temperature, the number of electrons released increases and the electrical conductivity increases.
This type of conduction is called intrinsic conduction.
Hence, both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

The electrical resistivity of a semiconductor:

  1. increases with temperature

  2. decreases with temperature

  3. increases at low temperature and then decreases

  4. does not change with temperature
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

As the temperature increase the electrons in the valence band get excited and jump into the conduction band and hence the conductance increases and conductance is inversely proportional to resistivity. Hence, resistivity decreases.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

Which of the following, when doped into ultrapure germanium, will convert it into a p-type semiconductor?

  1. $C$
  2. $As$
  3. $In$
  4. $Na$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When a pure semiconductor is doped with trivalent elemental impurity $p$ type semiconductors are formed

(A) $C\longrightarrow Tetravalent$
(B) $As\longrightarrow Pentavalent$
(C) $Indium$ $(In)\longrightarrow$ $Trivalent$
(D) $Na\longrightarrow$ $Monovalent$
Thus Indium ($In$) will convert ultrapure germanium into p-type semiconductor.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

Superconductivity may be defined as a phenomenon in which metals, alloys and chemical compounds become perfect conductors with zero resistivity at temperatures approaching __________.

  1. room temperature

  2. zero temperature

  3. absolute zero

  4. all of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Superconductivity may be defined as a phenomenon in which metals, alloys and chemical compounds become perfect conductors with zero resistivity at temperatures approaching absolute zero.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

Which of the following represent(s) true statement(s)?

  1. The electrical resistance of metal does not depends upon temperature.

  2. Electrical resistance increases with decrease in temperature.

  3. The electrical resistance becomes almost zero near the absolute temperature.

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The following represents true statements. The electrical resistance of metal depends upon temperature. Electrical resistance decreases with decrease in temperature. The electrical resistance becomes almost zero near the absolute temperature.

Multiple choice chemistry solid state electrical and magnetic properties of solids impurity defects properties of solids

The temperature at which a substance starts behaving as super-conductor is called _________.

  1. normal temperature

  2. transition temperature

  3. regular temperature

  4. all of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The temperature at which a substance starts behaving as super-conductor is called transition temperature. For most metals, the transition temperature lies between 2 and 5 K.