![]() The electrons not only carry charge, but also carry energy, so that thermal conductivity is proportional to the electrical conductivity. As temperature increases, the atoms vibrate more, and increasing the scattering of bounced electrons. These bounced electrons scatter and resist the current flow. The theory says that at high temperatures resistivity happens when electrons in the current bounce off of vibrating atoms. The classic theory of metals explains that resistivity increases with temperature, due to atoms vibrating more as the heat rises. A material's resistivity impedes this flow. The electrons in metals, such as the iron in Earth's core, carry current and heat. ![]() Their conclusion hinges on discovering that the classic theory of metals developed in the 1930's was incomplete. In their work, Cohen and Zhang, along with Kristjan Haule of Rutgers University, used a new computational physics method and found that the original thermal convection theory was right all along. But recent calculations called this theory into question, launching new quests for its explanation. It has long been thought that heat flow drives what is called thermal convection - the hottest liquid becomes less dense and rises, as the cooler, more-dense liquid sinks - in Earth's liquid iron core and generates Earth's magnetic field. The center of the Earth is very hot, and the flow of heat from the planet's center towards the surface is thought to drive most of the dynamics of the Earth, ranging from volcanoes to plate tectonics.
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