# Ohms Law – Lesson 4 Ohms Law basically defines the relationship between three physical properties of electricity: Volts; Ohms; Amps.

1. Volts: Also referred to as pressure of electricity. Defines movement of electricity. No Volts = No pressure = No movement. You basically have no movement when there is no path of an OPEN in the circuit. Volts are represented by the letter V. The technical term for it is Electromotive Force or the letter E. Scientists use E. Technicians use V.
2. Ohms: Represented by the Omega Ω. Define the resistance on a circuit. A circuit always has resistance. If it didn’t, your battery would explode if the wires are thick enough. Wires have a resistance. So, more than likely, they will burn up before the battery explodes. And by burning up, or melting down, they will create heat and an open in the in the circuit, and the process of the circuit would come to an end.
3. Amps: Represented by the letter A, define the quantity, or volume of current flow of electricity. If you were to compare a river to a hose, you could say that the river flows more than the hose. Therefore, if you bring it to electrical term: more Amps. From the idea of Intensity of flow, scientists prefer to reference amps by the letter I.

Ohms Law formulas:  E = R x I  or  I = E/R  or  R=E/I (scientific annotations) It means that when you have two values, you can calculate the other.

Let’s say you have a battery of 12 Volts, a bulb with a resistance of 2 Ohms.  You can calculate how many Amps flow in that circuit:  I=E/R  or  I=12V/2Ω  =>  6 Amps.

Therefore if you were to install a fuse to protect that circuit, it would have to be rated at least 6 Amps.

And if you were to install new wires, using a reference table, you would have to use a minimum of 20 gauge wires, maybe a little bigger, like an 18 gauge.  Yes, the smaller the number, the bigger the wire.  In aviation they like aluminum (lighter, but current carrying ability is less than copper).

Rules of thumb:

• The higher the resistance, the higher the voltage in front of it.
• R up = A down  (As resistance is increased, the flow decreases)
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