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  • Question

  • Which of these has lowest dielectric strength?


  • Options
  • A. Dry air
  • B. Wet air
  • C. Cotton
  • D. Paper

  • Correct Answer
  • Wet air 

    Explanation
    Cotton and paper have higher dielectric strength than air. Moisture decreases dielectric strength.

    Materials and Components problems

    Search Results

    • 1. The quantum numbers associated with electron motion are designed as

    • Options
    • A. a, b, c
    • B. h, k, l
    • C. n, m, l
    • D. h, n, l
      • Discuss
    • 2. When temperature is more than ferromagnetic curie temperature, the behaviour of a ferromagnetic material is similar to that of paramagnetic material.

    • Options
    • A. True
    • B. False
      • Discuss
    • 3. A parallel plate capacitor having C = 200 x 10-12 F has loss dielectric having tan ? = 4 x 10-4. At an ac voltage of f = 106 Hz and peak value 2 V, the dielectric losses are

    • Options
    • A. 10-8 W
    • B. 10-6 W
    • C. 10-4 W
    • D. 10-2 W
      • Discuss
    • 4. The temperature at which some materials become superconductors is called

    • Options
    • A. Transition temperature
    • B. Curie temperature
    • C. Neel temperature
    • D. Onnes temperature
      • Discuss
    • 5. In an homogeneous dielectric subjected to an electric field E, the dipole moment per unit volume is ?0(?r - 1) E.

    • Options
    • A. True
    • B. False
      • Discuss
    • 6. Transformer oil is

    • Options
    • A. refined vegetable oil
    • B. refined mineral oil
    • C. mixture of vegetable and mineral oil
    • D. none of the above
      • Discuss
    • 7. Resistivity of copper is lower than that of nickel. When a small percentage of copper is added to nickel, the resistivity

    • Options
    • A. increases
    • B. decreases
    • C. may increase or decrease
    • D. remains the same
      • Discuss
    • 8. For a superconductor, magnetisation M in a field H is

    • Options
    • A. extremely small
    • B. - H
    • C. - I
    • D. zero
      • Discuss
    • 9. As per Curie-Weiss law, the magnetic susceptibility of a material varies as

    • Options
    • A. T-2
    • B.
    • C. T
    • D. T2
      • Discuss
    • 10. The application of magnetic field to superconducting material

    • Options
    • A. increases transition temperature
    • B. decreases transition temperature
    • C. has no effect on transition temperature
    • D. may increase or decrease the transition temperature
      • Discuss

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