Electrical Conductivity Protocol

The purpose of this resource is to measure the conductivity of water at a freshwater hydrology site. Students calibrate and take electrical conductivity measurements using an electrical conductivity meter. Students estimate the total dissolved solids from the electrical conductivity measurements. Educational levels: Intermediate elementary, Middle school, High school, Primary elementary

Effects of a radially varying electrical conductivity on 3D numerical dynamos

The transition from liquid metal to silicate rock in the cores of the terrestrial planets is likely to be accompanied by a gradient in the composition of the outer core liquid. The electrical conductivity of a volatile enriched liquid alloy can be substantially lower than a light-element-depleted fluid found close to the inner core boundary. In this paper, we investigate the effect of radially variable electrical conductivity on planetary dynamo action using an electrical conductivity that decreases exponentially as a function of radius. We find that numerical solutions with continuous, radially outward decreasing electrical conductivity profiles result in strongly modified flow and magnetic field dynamics, compared to solutions with homogeneous electrical conductivity. The force balances at the top of the simulated fluid determine the overall character of the flow. The relationship between Coriolis and Lorentz forces near the outer boundary controls the flow and magnetic field intensity and morphology of the system. Our results imply that a low conductivity layer near the top of Mercury's liquid outer core is consistent with its weak magnetic field.Comment: 30 pages, 11 figures, 2 tables. To be published in Physics of Earth and Planetary Interiors (PEPI)

Carbon nanotubes and silver flakes filled epoxy resin for new hybrid conductive adhesives

Combining conductive micro and nanofillers is a new way to improve electrical conductivity. Micrometric silver flakes and nanometric carbon nanotubes (CNTs) exhibit high electrical conductivity. A new type of hybrid conductive adhesives filled with silver flakes and carbon nanotubes (DWCNTs or MWCNTs) were investigated. High electrical conductivity is measured as well as improved mechanical properties at room temperature. Small agglomerates and free MWCNTs dispersed in the silver/epoxy composites improve the electrical conductivity and a synergistic effect between MWCNTs and micro sized silver flakes is observed in hybrid composites. Glassy and rubbery storage moduli of the hybrid composites increase with increasing silver loading at fixed CNTs volume fraction. High value of the storage modulus, measured in DWCNTs/μAg hybrid composites at rubbery state, is caused by strong agglomeration of DWCNTs bundles. The electrical and mechanical properties are consistent with the morphologies of the hybrid composites characterized by SEM

Lorentz Force Electrical Impedance Tomography

This article describes a method called Lorentz Force Electrical Impedance Tomography. The electrical conductivity of biological tissues can be measured through their sonication in a magnetic field: the vibration of the tissues inside the field induces an electrical current by Lorentz force. This current, detected by electrodes placed around the sample, is proportional to the ultrasonic pressure, to the strength of the magnetic field and to the electrical conductivity gradient along the acoustic axis. By focusing at different places inside the sample, a map of the electrical conductivity gradient can be established. In this study experiments were conducted on a gelatin phantom and on a beef sample, successively placed in a 300 mT magnetic field and sonicated with an ultrasonic transducer focused at 21 cm emitting 500 kHz bursts. Although all interfaces are not visible, in this exploratory study a good correlation is observed between the electrical conductivity image and the ultrasonic image. This method offers an alternative to detecting pathologies invisible to standard ultrasonography

Fluctuations of electrical conductivity: a new source for astrophysical magnetic fields

We consider the generation of magnetic field by the flow of a fluid for which the electrical conductivity is nonuniform. A new amplification mechanism is found which leads to dynamo action for flows much simpler than those considered so far. In particular, the fluctuations of the electrical conductivity provide a way to bypass anti-dynamo theorems. For astrophysical objects, we show through three-dimensional global numerical simulations that the temperature-driven fluctuations of the electrical conductivity can amplify an otherwise decaying large scale equatorial dipolar field. This effect could play a role for the generation of the unusually tilted magnetic field of the iced giants Neptune and Uranus.Comment: Accepted in Phys.Rev.Let