(This article was translated from Japanese to English using DeepL.)

Thank you for your patience. Now it is time to explain the contents of Ohm’s law.

Ohm’s law is a law that describes the relationship between electric current, voltage, and resistance.

## Meaning of Ohm’s Law

Ohm’s law is expressed by the equation “*V=RI *“.

What does this equation mean?

Look closely at this equation. Does it resemble anything?

Yes, It has the same form as the proportionality equation “*y=ax *” we learned in math!

The meaning of *y=ax* is **“ x and y are proportional and their proportionality constant is a “**.

Applying this to Ohm’s law *V=RI* as it is, we get **“ I(Electric Current) and V(Voltage) are proportional and their proportionality constant is R(Resistance)”**.

Ohm’s law should be understood properly in this way, rather than by memorizing the equation.

## What do we assign to each symbol?

*I* and *V* appear in the Ohm’s law equation, but in textbooks they are simply written as “Electric Current” and “Voltage”. This is an oversimplification.

Those who view *V* simply as a voltage tend to assign the battery voltage to *V*.

However, **that is a mistake**.

Now let me tell you the exact wording. First, *R*. This is the value of the resistance.

Next is *I*, which is **“the magnitude of the electric current flowing through that resistance”**.

Finally, *V*. This is **“how much the voltage drops with that resistor”**.

**Note that battery voltage has nothing to do with Ohm’s law!**

The function of a resistor in a circuit was to reduce the voltage. If you have forgotten, please refer to the previous article.

https://www.yukimura-physics.com/entry/elemag-f06

Ohm’s law shows the relationship between the “falling voltage” and the “the magnitude of the flowing electric current”.

## Summary of this lecture

## Next Time

In this lecture, we have summarized the contents and formulas of Ohm’s law, but what is important is its usage.

In the next lecture, I will explain how Ohm’s law can be used in actual circuit problems.

https://www.yukimura-physics.com/entry/elemag-f08