# Electrodynamics: Choosing a referance point for finding the E field of an infinite shape

cemtu
Homework Statement:
What is the physical meaning of not being able to choose the referance point at the infinity for calculating the E field of an infinite object(or shape)?
Relevant Equations:
No equations are needed, only a clear and simple verbal explanation which explains the phenomenon is needed.
I know how the math does not allow us to chose the reference point at infinity for infinite objects but I need to understand the underlying physics reason, not math reason.

Homework Helper
Gold Member
2022 Award
Homework Statement:: What is the physical meaning of not being able to choose the referance point at the infinity for calculating the E field of an infinite object(or shape)?
Homework Equations:: No equations are needed, only a clear and simple verbal explanation which explains the phenomenon is needed.

I know how the math does not allow us to chose the reference point at infinity for infinite objects but I need to understand the underlying physics reason, not math reason.

Infinite objects are fundamentally unphysical. You cannot have an infinite charged plate; only a relatively large one.

The potential energy of a particle in the field of a uniformly charged infinite plate may be infinite. If the plate and particle are like charged, then there is no limit to the kinetic energy gained by the particle as it is repelled with constant force indefinitely. And, if the particle and plate are oppositely charged, then there is no limit to the kinetic energy that the particle may have if it starts from far away. The potential energy "at infinity" would, therefore, be infinite. Which is to say undefined.

cemtu
thank you but I did not understand your explanation.