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Name: Johanna
Status: educator
Age: 30s
Location: N/A
Country: N/A
Date: Thursday, August 22, 2002

Why is the letter "I" used to represent current in Ohm's law?

I am not aware of any particular significance of the choice of "i" to stand for current in Ohm's Law. Scientists choose symbols that may or may not have any "extrinsic meaning".

Examples: 1. Both "E" and "V" are used to stand for "voltage" in Ohm's Law.

2. Potential energy uses the symbols: "U"and "V".

3. Both the letters "x,y,z" and "i,j,k" are used to label coordination axes.

The "H" is used to mean the Hamiltonian operator in physics, but the enthalpy in thermodynamics. The point is, for many cases there is no significance to the choice of symbols, but sometimes there is. Even in those cases the "reason" is usually transparent, for example, the use of "e" for the charge on the electron.

Vince Calder


I do not know for a fact why, but I expect the word "current" was not always used. It is possible that a term such as influx of charge was once used.

To use the first letter would cause problems because both charge and current start with the same letter. "q" for charge and "I" for current may have just been chosen because they look very different.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College

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