Ohm's law

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Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. The constant of proportionality is known as the resistance and the relationship can be expressed as:

I = {U \over R},

where I is the current, U is the voltage an R the resistance.

Multiplying R on each side of the equation means this equation can also be written as:

U = R \cdot I,

which is probably how much people remember it.


Consider the following circuit:

Basic 1 p1.svg

consisting of a voltage source G1 (a battery or a power supply) of 1 V and a resistor R1 of 1 kΩ, the current I flowing through the circuit can be calculated as:

I = {1.5 V \over 1 k\Omega} =  {1.5 V \over 1 \cdot 10^3 \Omega} = 1.5 \cdot 10^{-3} A = 1.5 mA