We have created an experimental procedure for determining the temperature coefficient of resistivity, α R , introductory physics laboratories. As in from Henry, this method examines relationship between and resistivity to establish within 10% accepted value.

We show that the continuous cholesteric fingers, which form in homeotropic samples at the unwinding temperature of the cholesteric phase, drift and spiral when they are subjected to a temperature gradient. This phenomenon is attributed to the appearance of a Lehmann thermomechanical torque. Measurements of the finger drift velocity on both sides of the compensation temperature of a cholesteric ...

We consider a two-dimensional lattice model of equilibrium statistical mechanics, using nearest neighbor interactions based on the matching conditions for an aperiodic set of 16 Wang tiles. This model has uncountably many ground state configurations, all of which are nonperiodic. The question addressed in this paper is whether nonperiodicity persists at low but positive temperature. We present ...

Zn(CN)2 and Ni(CN)2 are known for exhibiting anomalous thermal expansion over a wide temperature range. The volume thermal expansion coefficient for the cubic, three dimensionally connected material, Zn(CN)2, is negative (αV = -51 × 10 -6 K) while for Ni(CN)2, a tetragonal material, the thermal expansion coefficient is negative in the two dimensionally connected sheets (αa=-7 × 10 -6 K), but th...

Temperature-dependent dc conductivity measurements and infrared reflectivity measurements ~20–9000 cm! were performed on a series of polyaniline samples with two different dopant acids at various doping levels. The typical fingerprints of a disordered metal such as a positive temperature coefficient of resistivity at high temperatures, a very high reflectivity in the far infrared, and a plasma ...

The gravitational coupling R& 2 plays a crucial role in determining the fate of the symmetric, high temperature state in a grand unified model with Coleman-Weinberg type symmetry breaking. If this term enters in the lagrangian with a negative sign, it drives the SU(5) breaking phase transition at a temperature of about 101° GeV. If it enters with a positive sign, and in particular with the coef...

We report magnetoresistivity measurements on strongly underdoped YBa2Cu3Ox (x56.25 and 6.36) single crystals in applied magnetic fields Hi c axis. We identify two different contributions to both in-plane Drab /rab and out-of-plane Drc /rc magnetoresistivities. The first contribution has the same sign as the temperature coefficient of the resistivity ] ln ri /]T (i5$c ,ab%). This contribution re...

Variable temperature transport between 1.4 and 300 K, structural imaging, and theoretical calculations were used to characterize the properties of electrically active 24 degrees and 36.8 degrees [001] tilt SrTiO3 grain boundaries with 0.1 at. % niobium doping. An anomaly in boundary resistance and capacitance characteristics typical of a positive temperature coefficient effect is observed. This...