Materials And Components MCQs

Practice and Learn through MCQs and Quizzes. W3Definitions.com have 285 Materials And Components MCQs

A 200 turn coil has a self inductance of 10 mH. If the number of turns is doubled, all other quantities remaining the same, the self inductance will be

  • A. 2.5 mH
  • B. 5 mH
  • C. 20 mH
  • D. 40 mH
  • Correct Answer: Option D

A capacitor can be represented by a capacitance and resistance in parallel. For a good capacitor, this parallel resistance should be

  • A. negligible
  • B. low
  • C. high
  • D. very high
  • Correct Answer: Option D

A circular sphere mile is the area of cross-section of a wire

  • A. having a diameter equal to 1 miles
  • B. having a radius equal to 1 miles
  • C. having a circumference equal to 1 miles
  • D. none of the above
  • Correct Answer: Option A

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

  • A. 2 N, + y direction
  • B. 2 N, - y direction
  • C. 0.02 N, + y direction
  • D. 0.02 N, - y direction
  • Correct Answer: Option B

A copper atom is neutral. Its core has a net charge of

  • B. + 1
  • C. - 1
  • D. + 2
  • Correct Answer: Option B

A copper specimen has resistivity equal to 1.8 x 10-8 ohm-m at room temperature. At a temperature of 700 K, the resistivity is likely to be

  • A. 1.6 x 10-8 Ω-m
  • B. 2 x 10-8 Ω-m
  • C. 3 x 10-8 Ω-m
  • D. 6 x 10-8 Ω-m
  • Correct Answer: Option D

A dielectric is subjected to alternating field. The dielectric losses are potential to

  • A. real part of dielectric constant
  • B. imaginary part of dielectric constant
  • C. both real and imaginary parts of dielectric constant
  • D. either real or imaginary part of dielectric constant
  • Correct Answer: Option B

A dielectric material must be

  • A. insulator
  • B. good conductor
  • C. resistor
  • D. semiconductor
  • Correct Answer: Option A

A dielectric of relative permittivity ∈r is subjected to a homogeneous electric field E. The dipole moment P per unit volume is given by

  • A. P = constant
  • B. P = ∈0 E
  • C. P = ∈0(∈r - 1) E
  • D. P = ∈r E
  • Correct Answer: Option C

A good dielectric should have

  • A. low losses
  • B. good heat conductivity
  • C. high intrinsic strength
  • D. all of the above
  • Correct Answer: Option D

A liquid has N permanent dipoles μp per unit volume and has been subjected to dc field for a long time such that orientation polarization is P0. At t = 0, the field is suddenly removed, then polarization

  • A. will remain constant at P0
  • B. will become zero at t = 0
  • C. will delay to zero with a time constant
  • D. either b or c
  • Correct Answer: Option C

A magnet does not attract

  • A. nickel
  • B. iron
  • C. copper
  • D. iron and copper
  • Correct Answer: Option C

A magnetic field exists around

  • A. moving charges
  • B. static charges
  • C. iron
  • D. copper
  • Correct Answer: Option A

A material which is lightly repelled by a magnetic field is known as

  • A. diamagnetic material
  • B. non-magnetic material
  • C. ferromagnetic material
  • D. paramagnetic material
  • Correct Answer: Option A

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

  • A. 10-8 W
  • B. 10-6 W
  • C. 10-4 W
  • D. 10-2 W
  • Correct Answer: Option B

A permeable substance is one

  • A. which is strong magnet
  • B. which is a weak magnet
  • C. which is a good conductor
  • D. through which magnetic lines of force can pass easily
  • Correct Answer: Option D

A photoconductor is a

  • A. conductor
  • B. semiconductor
  • C. insulator
  • D. superconductor
  • Correct Answer: Option B

A piece of copper and another piece of Germanium are cooled from 30°C to 80 K. The resistance of

  • A. copper decreases and germanium increases
  • B. both decreases
  • C. both increases
  • D. copper increases and germanium decreases
  • Correct Answer: Option A

A piece of iron is placed in a magnetic field

  • A. the magnetic field will not be affected
  • B. the magnetic lines of force will bend to pass through the piece
  • C. the magnetic lines of force will bend away from the piece
  • D. any of the above depending on type of iron
  • Correct Answer: Option B

A rare gas has N atoms per m3. If electronic polarizability of single atom of this gas is ae, then

  • A. ∈r = Ne
  • B. ∈0∈r = Ne
  • C. ∈0(∈r - 1) = Ne
  • D. ∈0(∈r - 2) = Ne
  • Correct Answer: Option C

A sample of N type semiconductor has an electron density of 6.25 x 1018/cm3 at 300 K. If intrinsic concentration of carriers in this sample is 2.5 x 1013/cm3 at this temperature, the hole density is

  • A. 106 / cm3
  • B. 108 / cm3
  • C. 1010 / cm3
  • D. 1012 / cm3
  • Correct Answer: Option B

A sheet of bakelite is inserted between the plates of an air capacitor. The capacitance will

  • A. increase
  • B. decrease
  • C. remain the same
  • D. may increase or decrease
  • Correct Answer: Option A

A single layer air cored coil has n turns and inductance L. If a new coil is formed by having 2n turns while keeping the coil length and diameter the same, the new inductance is

  • A. 0.5 L
  • B. L
  • C. 2 L
  • D. 4 L
  • Correct Answer: Option D

A wire is carrying current I. The field intensity H at a distance r from the wire

  • A. is directed towards wire
  • B. is directed away from wire
  • C. is tangential every where to a circle of radius r
  • D. none of the above
  • Correct Answer: Option C

Above a certain temperature, the specific heat of a metal becomes constant. This temperature is called

  • A. Debye temperature
  • B. Curie temperature
  • C. Neel temperature
  • D. Transition temperature
  • Correct Answer: Option A

An atom of a rare gas is placed is an electric field E. Then

  • A. the nucleus will be shifted in the direction of E by an amount which is proportional to E.
  • B. the nucleus will not be shifted.
  • C. the nucleus will be shifted in the direction of E by an amount which is independent of E.
  • D. the nucleus will be shifted in a direction opposite to that of E.
  • Correct Answer: Option A

An electrolytic capacitor can be used for

  • A. ac only
  • B. dc only
  • C. both ac and dc
  • D. high frequency ac
  • Correct Answer: Option B

An electron (charge -e) is rotating in a circular orbit of radius R, around a proton with charge +e at a constant angular velocity ω. The orbital magnetic dipole moment is

  • A. 0.5 eω R2
  • B. eω R2
  • C. 2 eω R2
  • D. 0.5 eω R3
  • Correct Answer: Option A

An electron in a homogeneous magnetic field and having velocity perpendicular to the direction of field moves

  • A. perpendicular to the field
  • B. along the field
  • C. along a straight line inclined at 45° to field
  • D. in a circular path
  • Correct Answer: Option D

An electron shell corresponding to principal quantum number n can contain a maximum of

  • A. n2 electrons
  • B. 2n2 electrons
  • C. 2n electron
  • D. n3 electron
  • Correct Answer: Option B

An iron specimen has µr = 1000 when B = 0.3 T. If B = 0.35 T, µr

  • A. will be 1000
  • B. will be less than 1000
  • C. will be more than 1000
  • D. may be more or less than 1000
  • Correct Answer: Option D

As per Matthiessen’s rule, the total resistivity r of a conductor can be written as r = ri + aT, where ri and a are constants and T is absolute temperature. At very low temperatures

  • A. aT = 0
  • B. aT > i
  • C. aT ∼ i
  • D. aT < i
  • Correct Answer: Option D

As per temperature limits, the number of categories of solid dielectrics are

  • A. 7
  • B. 6
  • C. 8
  • D. 5
  • Correct Answer: Option A

As regards ∈0 and ∈r (absolute and relative permittivity)

  • 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
  • Correct Answer: Option B

As regards dielectric constant εr

  • A. the units are farads/m
  • B. the units are newton/coulomb
  • C. it is dimensionless
  • D. the units are farads
  • Correct Answer: Option C

As regards ferromagnetic Curie temperature Qf and paramagnetic curie temperature θ

  • A. Qf > θ
  • B. θ > Qf
  • C. θ equal to or less than Qf
  • D. θ may be equal to less than or more Qf
  • Correct Answer: Option B

As the atoms of rare gases become larger, electronic polarizability

  • A. increases
  • B. decreases
  • C. remains the same
  • D. may increase or decrease
  • Correct Answer: Option C

As the temperature of a pure silicon specimen is increased

  • A. the number of free electrons increases
  • B. the number of holes decreases
  • C. the number of holes increases
  • D. the number of free electrons and holes increases
  • Correct Answer: Option D

As the temperature of semiconductor is increased

  • A. the average number of free charge carriers decreases
  • B. the average number of free charge carriers increases
  • C. the average number of free charge carriers remains the same
  • D. the average number of free charge carriers may increase or decrease
  • Correct Answer: Option B

As the viscosity of a liquid increases, the relaxation time

  • A. remains constant
  • B. increases
  • C. decreases
  • D. first decreases then increases
  • Correct Answer: Option B