Questions and Answers of Modern Physics

A steel wire is stretched with a stress of 70 MPa (10,000 psi) at 20°C (68°F). If the length is held constant, to what temperature must the wire be heated to reduce the stress to 17 MPa (2500 psi)?
If a cylindrical rod of brass 150.00 mm long and 10.000 mm in diameter is heated from 20°C to 160°C while its ends are maintained rigid, determine its change in diameter. Hint: You may want to
The two ends of a cylindrical rod of nickel 120.00 mm long and 12.000 mm in diameter are maintained rigid. If the rod is initially at 70°C, to what temperature must it be cooled in order to have a
Which of the following sets of properties leads to a high degree of thermal shock resistance? (A) High fracture strength High thermal conductivity High modulus of elasticity High coefficient of
To what temperature would 23.0 kg of some material at 100°C be raised if 255 kJ of heat is supplied? Assume a cp value of 423 J/kg-K for this material.(A) 26.2°C(B) 73.8°C(C) 126°C(D) 152°C
For copper, the heat capacity at constant volume Cv at 20 K is 0.38 J/mol-K and the Debye temperature is 340 K. Estimate the specific heat for the following:(a) at 40 K(b) at 400 K
A rod of some material 0.50 m long elongates 0.40 mm on heating from 50°C to 151°C. What is the value of the linear coefficient of thermal expansion for this material?(A) 5.30 ( 10-6 (°C)-1(B)
A copper wire 15 m (49.2 ft) long is cooled from 40°C to -9°C (104°F to 15°F). How much change in length does it experience?
A 0.4-m (15.7-in.) rod of a metal elongates 0.48 mm (0.019 in.) on heating from 20°C to 100°C (68°F to 212°F). Determine the value of the linear coefficient of thermal expansion for this material.
Briefly explain thermal expansion using the potential energy-versus-interatomic spacing curve.
A coil of wire 0.25 m long and having 400 turns carries a current of 15 A.(a)What is the magnitude of the magnetic field strength H?(b)Compute the flux density B if the coil is in a vacuum.(c)Compute
Estimate (a) the saturation magnetization and (b) the saturation flux density of cobalt ferrite [(CoFe2O4)8], which has a unit cell edge length of 0.838 nm.
The chemical formula for copper ferrite may be written as (CuFe2O4)8 because there are eight formula units per unit cell. If this material has a saturation magnetization of 1.35 × 105A/m and a
The formula for samarium iron garnet (Sm3Fe5O12) may be written in the form Sm3Fe2a Fe3dO12 where the superscripts a, c, and d represent different sites on which the Sm3+ and Fe3+ ions are located.
A coil of wire 0.5 m long and having 20 turns carries a current of 1.0 A.(a) Compute the flux density if the coil is within a vacuum.(b)A bar of an iron-silicon alloy, the B-H behavior for which is
A ferromagnetic material has a remanence of 1.0 tesla and a coercivity of 15,000 A/m. Saturation is achieved at a magnetic field strength of 25,000 A/m, at which the flux density is 1.25 teslas.
The following data are for a plain carbon steel alloy:(a)Construct a graph of B versus H.(b)What are the values of the initial permeability and initial relative permeability?(c)What is the value of
Which of the following pairs of materials displays ferromagnetic behavior? (A) Aluminum oxide and copper (B) Aluminum and titanium (C) MnO and Fe3O4 (D) Iron (α-ferrite) and nickel
A bar of an iron-silicon alloy having the B-H behavior shown in Figure 20.29 is inserted within a coil of wire 0.40 m long and having 50 turns through which passes a current of 0.1 A. (a) What is the
Estimate saturation values of H for single-crystal nickel in the [100], [110], and [111] directions.
Assume the silicon-iron (97 Fe, 3 Si) in Table 20.5 just reaches the point of saturation when inserted within the coil in Problem 20.1. Compute the saturation magnetization.
Figure 20.30 shows the B-versus-H curve for a nickel-iron alloy.(a)What is the saturation flux density?(b)What is the saturation magnetization?(c)What is the remanence?(d)What is the coercivity?(e)On
For a superconducting material at a temperature T below the critical temperature TC, the critical field HC(T) depends on temperature according to the relationshipWhere HC(0) is the critical field at
Using Equation 20.14, determine which of the superconducting elements in Table 20.7 are superconducting at 2 K and a magnetic field of 40,000 A/m.
The magnetization within a bar of some metal alloy is 4.6 ( 105 A/m at an H field of 52 A/m. What is this alloy's magnetic susceptibility?(A) 1.13 ( 10(4(B) 8.85 ( 103(C) 1.11 ( 10(2 H/m(D) 5.78 (
The magnetic flux density within a bar of some material is 0.630 tesla at an H field of 5 × 105A/m. Compute the following for this material:(a) The magnetic permeability(b) The magnetic
The magnetization within a bar of some metal alloy is 1.2 × 106A/m at an H field of 200 A/m. Compute the following:(a) The magnetic susceptibility,(b) The permeability,(c) The magnetic flux density
Compute (a) the saturation magnetization and (b) the saturation flux density for iron, which has a net magnetic moment per atom of 2.2 Bohr magnetons and a density of 7.87 g/cm3.
Confirm that there are 1.72 Bohr magnetons associated with each cobalt atom, given that the saturation magnetization is 1.45 × 106A/m, that cobalt has an HCP crystal structure with an atomic radius
Assume there exists some hypothetical metal that exhibits ferromagnetic behavior and that has (1) a simple cubic crystal structure (Figure 3.3), (2) an atomic radius of 0.125 nm, and (3) a saturation
What is the energy (in eV) of a photon of light having a wavelength of 3.9 × 10-7 m?(A) 1.61 eV(B) 3.18 eV(C) 31.8 eV(D) 9.44 eV
It is desired that the reflectivity of light at normal incidence to the surface of a transparent medium be less than 5.0%. Which of the following materials in Table 21.1 are likely candidates:
The index of refraction of quartz is anisotropic. Suppose that visible light is passing from one grain to another of different crystallographic orientation and at normal incidence to the grain
Zincselenide has a band gap of 2.58 eV. Over what range of wavelengths of visible light is it transparent?
The fraction of nonreflected radiation that is transmitted through a 5-mm thickness of a transparent material is 0.95. If the thickness is increased to 12 mm, what fraction of light will be
Thetransmissivity T of a transparent material 15 mm thick to normally incident light is 0.80. If the index of refraction of this material is 1.5, compute the thickness of material that will yield a
A completely amorphous and nonporous polymer will be: (A) Transparent (B) Translucent (C) Opaque (D) Ferromagnetic
Describe the three absorption mechanisms in nonmetallic materials.
In your own words, briefly describe the phenomenon of photoconductivity.
In your own words, describe how a ruby laser operates.
In ionic materials, how does the size of the component ions affect the extent of electronic polarization?
Compute the velocity of light in diamond, which has a dielectric constant r of 5.5 (at frequencies within the visible range) and a magnetic susceptibility of -2.17 × 10-5.
The indices of refraction of fused silica and polystyrene within the visible spectrum are 1.458 and 1.60, respectively. For each of these materials determine the fraction of the relative dielectric
Using the data in Table 21.1, estimate the dielectric constants for silica glass (fused silica), soda-lime glass, polytetrafluoroethylene, polyethylene, and polystyrene, and compare these values with

Showing 8200 - 8300 of 8244