Why is Electric Potential Energy Defined in the Y-Direction Only?

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SUMMARY

The discussion centers on the definition of electric potential energy in the y-direction, specifically referencing the equations for gravitational force and electric potential energy. The expressions used are F = mg for gravitational force and U = mgy for gravitational potential energy, which are inherently negative in the y-direction due to gravity. In contrast, the electric force is described by Fy = -q0*E and the potential energy by U = q0*Ey, leading to confusion about the directional dependence of electric fields. The consensus is that the uniformity of the electric field justifies the focus on the y-component in these equations.

PREREQUISITES
  • Understanding of basic mechanics, specifically force and energy concepts.
  • Familiarity with electric fields and their properties.
  • Knowledge of point charge interactions and Coulomb's law.
  • Basic grasp of vector components in physics.
NEXT STEPS
  • Study the concept of uniform electric fields and their implications on force and energy.
  • Learn about vector decomposition in electric fields and how to analyze forces in different directions.
  • Explore the relationship between electric potential energy and electric field strength.
  • Investigate the applications of electric potential energy in various physical systems.
USEFUL FOR

Students of physics, educators teaching mechanics and electromagnetism, and anyone seeking to deepen their understanding of electric potential energy and its directional dependencies.

Seraph404
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My book first introduces expressions for work and energy by referring to concepts from mechanics and gravitation. It uses the familiar expressions F =mg (-y direction) & U=mgy to explain the expressions it gives for electric potential energy. However... I understand that the force due to gravity in the first couple of expressions is always downward, hence the negative y-direction. But when it gives the expressions for force and potential energy of a point charge, Fy = -q0*E & U = q0*Ey, I don't understsand why they define it with only the y-component. Doesn't it depend on the direction of your electric field? I mean... electric field doesn't always have to be in the y-direction, right?
 
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Ah, never mind. I think it had to do with the fact that the electric field was uniform, so there was only one direction for the force to be exerted. Sorry about that.
 

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