Why is the equation for heat flow negative?

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SUMMARY

The equation for heat flow, represented as q = -k(dp/dx), indicates that heat flows from regions of higher thermal energy density to lower thermal energy density. The negative sign in the equation signifies that the direction of heat flow is opposite to the gradient of thermal energy density. This means that as heat moves from hot to cold, the thermal energy density decreases, aligning with the fundamental principle of thermodynamics that heat transfers from higher to lower temperatures.

PREREQUISITES
  • Understanding of thermodynamics principles
  • Familiarity with the concept of thermal energy density
  • Knowledge of calculus, specifically derivatives
  • Basic grasp of heat transfer mechanisms
NEXT STEPS
  • Study the laws of thermodynamics in detail
  • Learn about Fourier's law of heat conduction
  • Explore the concept of thermal gradients in different materials
  • Investigate the role of thermal conductivity (k) in heat transfer
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Students studying physics, particularly those focusing on thermodynamics, as well as educators and professionals involved in heat transfer analysis and thermal management.

Vitani11
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Homework Statement


q = -kdp/dx

Homework Equations



q = heat flow
k = constant
p = thermal energy density

The Attempt at a Solution


This equation says that when heat flows from hot to cold the thermal energy density increases but why? I thought heat meant a higher thermal energy density and hot to cold meant a lower energy density since the molecules that make up the air are slower when cold.
 
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