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  • Question

  • Assertion (A): For most metals, Fermi energy EF is less than 10 eV.

    Reason (R): Fermi level of a metal is given by EF = 3.64 x 10-19 (n)2/3 where n is number of free electrons/m3 of metal.


  • Options
  • A. Both A and R are true and R is correct explanation of A
  • B. Both A and R are true but R is not correct explanation of A
  • C. A is true but R is false
  • D. A is false but R is true

  • Correct Answer
  • Both A and R are true and R is correct explanation of A 

    • Materials and Components problems

    Search Results

    • 1. For a polyatomic gas, the equation relating dielectric constant ?r with molecular properties is

    • Options
    • A.
    • B.
    • C.
    • D.
      • Discuss
    • 2. When a pentavalent impurity is added, the semiconductor becomes

    • Options
    • A. p type
    • B. n type
    • C. intrinsic
    • D. neutral
      • Discuss
    • 3. Assertion (A): Orbital magnetic moment of an electron in an atom is of the order of 1 Bohr magneton.

      Reason (R): 1 Bohr magneton = 9.27 x 10-24 A/m2.


    • Options
    • A. Both A and R are true and R is correct explanation of A
    • B. Both A and R are true but R is not correct explanation of A
    • C. A is true but R is false
    • D. A is false but R is true
      • Discuss
    • 4. Assertion (A): An electron having charge - e and mass m and lying in an electric field E is subjected to an acceleration - (e/m) E.

      Reason (R): If there are n electrons/m3 moving with velocity vx and each electron has a charge - e, the current density J = - n evx.


    • Options
    • A. Both A and R are true and R is correct explanation of A
    • B. Both A and R are true but R is not correct explanation of A
    • C. A is true but R is false
    • D. A is false but R is true
      • Discuss
    • 5. Which solid dielectric has highest temperature limit?

    • Options
    • A. E
    • B. H
    • C. C
    • D. F
      • Discuss
    • 6. The relaxation time of electrons in a metal is of the order of

    • Options
    • A. 10-6 secs
    • B. 10-10 secs
    • C. 10-14 secs
    • D. 10-20 secs
      • Discuss
    • 7. As regards ?0 and ?r (absolute and relative permittivity)

    • Options
    • A. both ?0 and ?r can be interpreted in terms of atomic properties of medium
    • B. only ?r can be interpreted in terms of atomic properties of medium
    • C. only ?0 can be interpreted in terms of atomic properties
    • D. ?r has no physical significance
      • Discuss
    • 8. An electron is moving in a circular orbit of radius R at angular velocity ?0 in a field free space. If a magnetic field B is created, the velocity of electron ? will be given by the equation

    • Options
    • A.
    • B.
    • C.
    • D.
      • Discuss
    • 9. Even at room temperature, an intrinsic semiconductor has some holes. These holes are due to

    • Options
    • A. electron
    • B. doping
    • C. thermal energy
    • D. free electrons
      • Discuss
    • 10. At a very low temperature, a semiconductor

    • Options
    • A. becomes a conductor
    • B. becomes an insulator
    • C. may become a conductor or an insulator
    • D. will remain a semiconductor becomes a conductor or an insulator
      • Discuss

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