LC-circuit calorimetry

Abstract

We present a new type of calorimeter in which we couple an unknown heat capacity with the aid of Peltier elements to an electrical circuit. The use of an electrical inductance and an amplifier in the circuit allows us to achieve autonomous oscillations, and the measurement of the corresponding resonance frequency makes it possible to accurately measure the heat capacity with an intrinsic statistical uncertainty that decreases as ∼ t −3/2 m with measuring time t m , as opposed to a corresponding uncer-in the conventional alternating current (a.c.) method to measure heat capacities. We have built a demonstration experiment to show the feasibility of the new technique, and we have tested it on a gadolinium sample at its transition to the ferromagnetic state.

Heat flowing from cold to hot without external intervention by using a “thermal inductor”

“…Thus, we can interpret the role of the circuit as that of a thermal inductor. In analogy to the self-inductance L of an electrical inductor generating a voltage difference Δ V according to italicLtrueI.=−normalΔitalicV, we can even ascribe to the present circuit a thermal self-inductance L th = L /(α 2 T r ) ( 17 ), obeying LthtrueI.th=LthtrueQ¨=−normalΔitalicT (see section S4).…”

“…The considered thermal connection consists of an ideal electrical inductor with inductance L and a Peltier element with Peltier coefficient Π = α T , forming a closed electrical circuit (Fig. 2A) ( 17 ). Here, α stands for the combined Seebeck coefficient of the used thermoelectric materials and T is the absolute temperature of the considered junction between these materials.…”

“…In this article, we describe a simple thermal connection containing a novel thermal element, namely, the equivalent of a "thermal inductor" that we had originally designed for precise heat-capacity measurements in an actively driven thermal circuit (17). We show that it can also act in a passive way without any external or internally hidden source of power, and is able to drive the temperature difference between two massive bodies to change sign by imposing a certain thermal inertia on the flow of heat.…”

Reverse Heat Flow with Peltier-Induced Thermoinductive Effect

“…A Peltier-induced reverse heat flow has the advantage of easy tunability using an external current source, in contrast with previously proposed circuits, using external electrical coils 21,24 and natural convection 22,23 . For example, the control of heat flow in a fluid system is difficult because the exact analytical model and required experimental conditions are still unclear.…”

“…This is because oscillatory behaviors, with a reversal in the direction of heat flow from cold to hot, are typically considered violations of the second law of thermodynamics Error! Reference source not found., 21 . An equivalent of the "thermoinductive" effect has been reported in circuits provided with unclear and cumbersome interventions using external heat flows (i.e., natural convection) 22,23 , or the cooling of an electrical coil to the temperature of liquid He 24 .…”