Voltage is the difference in charge between two points. It is measured in volts, and represented in equations and schematics by the letter `V`.

Current is the rate at which charge is flowing. Current is measured in Amperes (usually just referred to as “Amps”). Amps are represented in equations by the letter `I`.

Resistance is a material’s tendency to resist the flow of charge (current). Unit of resistance is “1 Ohm”, defined as the resistance between two points in a conductor where the application of 1 volt will push 1 ampere, or 6.241×10^18 electrons. This value is usually represented in schematics with the greek letter `Ω`, which is called omega, and pronounced “ohm”.

## Ohm’s Law

Combining the elements of voltage, current, and resistance, Ohm developed the formula:

V = I * R

Where

• V = Voltage in volts
• I = Current in amps
• R = Resistance in ohms

## Kirchhoff’s First Law

Summation of all Current in any point of circuit equals to `0`.

## Kirchhoff’s Second Law

Summation of all Voltage in any Loop always equals to `0`.