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If it isn't just a word, and it isn't really something to be memorized in order to pass a test, what do the letters in Ohm's Law really mean?

By Douglas Krantz

E = I x R is a formula used to figure out the Voltage "E", or the Current "I", or the Resistance "R" of an electrical or electronic circuit.

The electrons are found in layered clouds around the nucleus of atoms. The protons in the atom don't move from atom to atom, but the electrons can be pushed and pulled from atom to atom using electrical force. The force is called Electromotive Force (EMF). EMF is measured in voltage.

The letters in Ohm's Law show a relationship between voltage, current, and resistance, and at the heart of that relationship is the electron.

"E" stands for Electromotive Force (EMF). It's the driving muscle that moves the electrons.

Measured in Voltage, EMF pushes and pulls on the electrons.

"I" stands for "Intensité de Courant" (French), or Current Intensity. André-Marie Ampere, who discovered electrical current, used this symbol.

Movement

Measured in Amps, and hopping from one atom to the next, the organized movement of electrons going past a point is electrical current, or "I".

"R" stands for Resistance. It restricts, or slows down, the movement of electrons.

Electron Flow

Measured in Ohms, resistance opposes electron flow. The greater the resistance, the less the electrons flow.

Assuming the electromotive force remains the same, reducing the resistance, like opening a valve on a water pipe, will increase the number of electrons that flow.

The opposite is also true, increasing the resistance will reduce the number of electrons that flow.

The quantity of electrons flowing, electrical current, is determined by the electromotive force - reduced by the resistance.

Similarly, the quantity of water flowing is determined by water pressure, reduced by the restriction of the pipe.

The amount of electromotive force (voltage) directly affects current flow. Current goes up and down as EMF goes up and down.

The amount of resistance inversely affects current flow. As resistance goes up, current goes down, and as resistance goes down, current goes up.

The relationships between the electromotive force, current and resistance are all interrelated, and described in a single formula, or law.

The Formula is

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