Ohm’s Law and Power

Ohm’s Law and Power

While we may not realize it in the beginning, we are using and relying on Ohm’s Law when we vape. Ultimately, a Vapour Device (Electronic Cigarette) is nothing more than a Direct Current (DC) Circuit with a Resistor (Coil Head) that heats up when we turn in on.

This fact becomes more evident and CRITICAL if you evolve into building your own coils and/or work with MOD or Low Resistance Devices.

Why is this important?

Battery safety! Batteries are inherently dangerous if they are not handled properly because they are able to store a tremendous amount of power in a very small device. Every battery is "rated" for a certain amount of electrical current (Amperage) where it can safely operate, as well as a maximum lever where it becomes unsafe. These values come from the manufacturer and they are provided to ensure that the applied use of the battery does not exceed the designed capabilities.

If you only use regulated devices with built-in batteries, this is not necessarily something that you need to know or care about. But it could still be a good to know and understand what different power and voltages will do for your device.

However, if you become a more advanced or hobbyist vaper, Ohm’s Law should be used to ensure that that you have a proper battery for the atomizing device that you are using. For example: Bad things will happen if you use a battery rated for 10 amps in a device build to create 15 amps of current.

For that reason alone, it is imperative that users of advanced devices be familiar with Ohm’s Law.

Also, in the case of more advanced devices where multiple Li-ion batteries are used, it is important that all of the batteries be of the same type and rating among other things. Understanding the difference between having batteries in series vs. parallel is also a key to knowing the limitations of the battery "pack" (two or more batteries).

Below is a detailed explanation of Ohm’s Law to include relationships and formulas that should be used in doing your own calculations. Much of this information is sourced from Electronics Tutorials.

If you just want to get to the calculations, click here

Ohm’s Law and Power

Ohm’s Law

The relationship between Voltage, Current and Resistance in any DC electrical circuit was firstly discovered by the German physicist Georg Ohm. Ohm found 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. This relationship between the Voltage, Current and Resistance forms the bases of Ohms Law.

Ohms Law Triangle

Here the three quantities of V (Volts), I (Current or Amps) and R (Resistance) have been superimposed into a triangle (affectionately called the Ohms Law Triangle) giving voltage at the top with current and resistance at the bottom. This arrangement represents the actual position of each quantity in the Ohms law formulas.

Ohm's Law Relationship

and transposing the above Ohms Law equation gives us the following combinations of the same equation:

Ohm's Law Relationship

Then by using Ohms Law we can see that a voltage of 1V applied to a resistor of 1Ω will cause a current of 1A to flow and the greater the resistance, the less current will flow for any applied voltage.

Electrical Power in Circuits

Electrical Power, ( P ) in a circuit is the amount of energy that is absorbed or produced within the circuit. A source of energy such as a voltage will produce or deliver power while the connected load absorbs it. Light bulbs and heaters for example, absorb power and convert it into heat or light and the higher their value or rating in watts the more power they will consume.

The quantity symbol for power is P and is the product of voltage multiplied by the current with the unit of measurement being the Watt ( W ).

The Power Triangle

Again, the three quantities have been superimposed into a triangle this time called the Power Triangle with power at the top and current and voltage at the bottom. Again, this arrangement represents the actual position of each quantity in the Ohms law power formulas.

Ohm's Law Power Relationship

and again, transposing the basic Ohms Law equation above for power gives us the following combinations of the same equation to find the various individual quantities:

Ohm's Law Relationship

So we can see that there are three possible formulas for calculating electrical power in a circuit. If the calculated power is positive, (+P) in value for any formula the component absorbs the power, that is it is consuming or using power. But if the calculated power is negative, (-P) in value the component produces or generates power, in other words it is a source of electrical power such as batteries and generators.

Ohms Law Pie Chart

To help us understand the relationship between the various values a little further, we can take all of Ohm’s Law equations from above for finding Voltage, Current, Resistance and Power and condense them into a simple Ohms Law pie chart for use in AC and DC circuits and calculations as shown.

Ohm's Law Pie Chart"

Ohms Law Matrix Table

As well as using the Ohm’s Law Pie Chart shown above, we can also put the individual Ohm’s Law equations into a simple matrix table as shown for easy reference when calculating an unknown value.

Ohm's Law Matrix Table



Calculate Watts (Power)

To calculate the circuit power…
The formula is P = I × V or,
P = R × I2 or,
P = V2 / R
Enter any two factors of V, I, and R
Voltage (V) Current (I) Resistance (R)

Calculated Power

Calculate Amperes

To calculate the circuit amperage…
The formula is I = V / R or,
I = P / V or,
I = (P / R)2
Enter any two factors of V, P, and R
Voltage (V) Power (P) Resistance (R)

Calculated Amperage

Calculate Volts

To calculate the circuit voltage…
The formula is V = I x R or,
V = (P x R)2 or,
V = P / I
Enter any two factors of P, I, and R
Power (P) Current (I) Resistance (R)

Calculated Voltage

Calculate Ohms

To calculate the circuit resistance…
The formula is R = V / I
R = V2 / P or,
R = P / I2
Enter any two factors of V, I, and P
Voltage (V) Current (I) Power (P)

Calculated Resistance

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