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  • Question
  • Assertion (A): Hall effect is used to determine whether the semi- conductor is p or n type.

    Reason (R): Under the influence of field, holes and electrons move in opposite direction.


  • 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


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    • 1. The core of a solenoid is made of material of relative permeability ?r. A small cavity area dA and length dl is cut in the core. If it is desired that flux density in the cavity should be equal to B0

    • Options
    • A. the fields inside and outside the cavity must be equal
    • B. the field inside the cavity must be made stronger than field outside the cavity
    • C. the field inside the cavity must be made weaker than the field outside the cavity
    • D. none of the above
    • Discuss
    • 2. A conductor carries 10 A current in + x direction and is lying in a field having a flux density 0.2 T directed along + z direction. The magnitude of force per metre length and direction are

    • Options
    • A. 2 N, + y direction
    • B. 2 N, - y direction
    • C. 0.02 N, + y direction
    • D. 0.02 N, - y direction
    • Discuss
    • 3. If a small amount of Cu is added to Ni conductor, then

    • Options
    • A. resistivity of Ni will decrease at all temperatures because Cu is a better conductor than Ni
    • B. residual resistivity of Ni at low temperature will increase as Cu atoms act as defect centres
    • C. resistivity of Ni will increase at all temperatures as Cu destroys the periodicity of Ni and acts as defects
    • D. resistivity of Ni remains the same
    • Discuss
    • 4. The unit for mmf is

    • Options
    • A. A
    • B. Wb
    • C. T
    • D. V
    • Discuss
    • 5. Electrical contact materials used in switches, brushes, relay must possess

    • Options
    • A. high thermal conductivity and high melting point
    • B. low thermal conductivity and low melting point
    • C. high thermal conductivity and low melting point
    • D. low thermal conductivity and high melting point
    • Discuss
    • 6. In terms of Planck's constant h, the orbital angular momentum of an electron is

    • Options
    • A. h
    • B.
    • C. 2ph
    • D.
    • Discuss
    • 7. The induced magnetic dipole moment is independent of the permanent magnetic dipole moment.

    • Options
    • A. True
    • B. False
    • Discuss
    • 8. When a material is in superconducting state and a magnetic field is applied

    • Options
    • A. the superconducting property is not affected
    • B. the superconducting property may be affected and resistivity may increase from zero to a low value
    • C. the superconducting property may be destroyed
    • D. the material may become an insulator
    • Discuss
    • 9. Nickel is a non-magnetic material.

    • Options
    • A. True
    • B. False
    • Discuss
    • 10. An electron is moving around a proton, in a circle of radius R. If flux density in the region is increased from zero to B, the force on the electron is

    • Options
    • A.
    • B. eR (dB / dt)
    • C. eRB
    • D.
    • Discuss


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