Ohm’s Law (coulomb, Ampere, volt, resistance, current)

Ohm’s Law (coulomb, Ampere, volt, resistance, current)


  • A coulomb is a quantity measurement of electrons created by Charles-Augustin de Coulumb. One coulomb contains 6.25 x 10(18) electrons.
  • One coulomb contains 6,250,000,000,000,000,000 electrons. (Imagine a bunch of billion electrons put together)
  • Thus, it takes 6.25 x 10(18) electrons to make one coulomb.
  • Again, the coulomb itself is only a quantity measurement of electrons (or electricity).
You see that electron ?, it takes 6.25 x 10 (18) electrons to be called one coulomb.


  • Ampere, or amp is a quantity measurement of coulombs (or electricity) combined with a time measurement (by second).
  • If a coulomb is only a quantity measurement, then a amp is a quantity measurement of electricity plus time measurement
  • Thus, one amp equals one coulomb per second. In another word, one amp of current flows through a conductor when one coulomb flows past a certain point on by on one second.  (1 amp = 1 coulomb / 1 sec )
  • If one coulomb were to flow past a point in a half second, there would be 2 amperes of current flow. (2 amps = 1 coulomb / (1/2 sec))
  • If one coulomb were to flow past a point in two seconds there would be a half amp of flow. (0.5 amp = 1 coulomb / 2 sec)
  • Current (or amount of electricity) is measured and expressed in amps.


  • Voltage (or electromotive force, in short EMF) is the force that pushes electrons through wires and circuits.
  • Just like water being pushed through a hose, in a circuit or wire, it is the voltage (often referred to as electrical force) that pushes current (or billions of electrons).
  • If you are still confused about the clear difference between the volt, current and resistance, then read up on my explanation of the three measurements because understanding basic electricity is crucial in HVAC fields.


  • Ohm refers to resistance. Resistance is an electrical force that works against voltage.
  • Therefore, in order for current to pass through a wire or circuit, the voltage (electrical pressure that pushes electrons) must be greater than the force of resistance.
  • Resistance, however is a necessary electrical force in any electrical system. Low resistance or no resistance in a wire or circuit will allow an excessive amount of electrons to flow and cause a  short circuit.
  • If you compare resistance (ohms) to a water system, it would be some thing like a reducer to control the water.
  • In an electrical system, it is the resistor that controls the flow of electrons.
  • Resistance is one one of the current-limiting forces in a wire or circuit. There are other current-limiting sources such as Inductive reactance and captacitve reactance.
  • All of these current-limiting qualities including resistance refer to impedance.
  • Impedance is the quantity generally used to describe the current -limiting force in an alternating current circuit.


  • Wattage (or power) is a measure of the amount of power that is being used in the circuit. It is proportional to the amount of voltage and the amount of current flow.
  • A watt equals a joule per second.
  • It is proportional to the amount of voltage and the amount of current flow. (W = V * A)
  • Wattage (or power) is expressed as “W”


Ohm’s law

  • Ohm’s law discovered by Germany scientist “George S. Ohm” is a law that states all electrical quantities are proportional to each other and can therefore be expressed as mathematical formulas.
  • A more detailed version of Ohm’s law states that “at a constant temperature, the electrical current flowing through a fixed linear resistance is directly proportional to the voltage applied across it, and also inversely proportional to the resistance”.
  • In its simplest form, it states that it takes 1 volt to push 1 amp through 1 ohm.

Metric Prefixes

  • In the electrical field, the engineering notation is used in stead of the standard metric prefixes.
  • Engineering notation is in the steps of one thousand instead of ten.


About Hvac Master 32 Articles
All about Heating Ventilation Air Conditioning, property management, and etc