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

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Electric potential energy is often defined in the y-direction due to the use of uniform electric fields in introductory physics. The expressions for force and potential energy, such as Fy = -q0*E and U = q0*Ey, are derived under the assumption of a consistent direction for the electric field. While electric fields can exist in multiple directions, focusing on the y-component simplifies the explanation and aligns with gravitational force concepts. The discussion acknowledges that this simplification is valid when the electric field is uniform. Understanding this context clarifies the reasoning behind the directional definition of electric potential energy.
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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