Ohm's Law

Ohm's law is of enormous importance in electrical engineering.

The law shows the relationship between the major electrical quantities; amperage, voltage and resistance: In a conductor or in an electrical element voltage and amperage are proportional to each other. If voltage U rises, amperage I rises, too, by the same factor.

The URI-formula is a mathematical representation of this law:

U = R ⋅ I with

U voltage
R resistance
I amperage

If we know two of the quantities - amperage, voltage and resistance, we can calculate the third quantity. All we have to do for that is to rearrange the formula so that we have the missing quantity separate.

Fred thinks: "the higher the resistance R the lower is the amperage I, if the voltage U remains the same."
Is this correct?

Click here to reveal the solution.

Yes, Fred is right.
If the voltage remains the same, the pressure that drives the electrons through the conductor doesn't change. But if the electrons are hindered to pass through the conductor because of the higher resistance less electrons manage pass through the conductor during the same period of time - amperage decreases. For amperage is telling us how many electrons pass the conductor within a certain period of time.