Voltage drop across resistors, in this case, resistance wire

[John_]

I understand that voltage will drop when it flows through something that does work. The most common example I can think of would be wire. When electricity flows through wire it loses some of it's power because the wire has a resistance (this energy is lost as heat), over short distances this drop can be negligible, but it is why we can't run wires across extremely great distances without some sort of hub. I understand the basic concept around this, a load in a circuit be it a resistor, a light bulb, a motor performs work, the work uses energy. The energy is turned into heat, movement, whatever.

With resistance wire, the voltage drops because the wire is heating up and using the energy. Say we have a battery outputting 4.2V, with no load the mod the battery is in is capable of delivering that 4.2V minus a negligible drop. When we attach a coil to the top of that mod, we can measure how much the voltage has dropped across it. Say the voltage drops 0.4 Volts so we're reading 3.8V. Now here's my question, does the entire heating coil see the power of 4.2V or does it drop as it flows through the wire? coils heat up from the center out, shouldn't they heat up from the negative end toward the positive end?

Thank you for your time guys.

 

[100%VG]

As I see it, this is a two-part question...

The coil normally heats up from the center, out, because the difference in potential from (+) to (-) is felt the greatest in the middle. This is true on a properly wrapped coil, especially on Silica and Cotton. If there are places in the wire of the coil on a SS Mesh wick where the wire doesn't make contact with the wick, it may glow red there first. If the coil is wrapped on an improperly oxidized SS Mesh wick, there will be shorts to ground, via the wick touching the Deck (which is ground), so the top wrap may glow and pop. If there are no shorts to ground on the wick, like in the RSST, where the wick is insulated from ground, the coil will burn in at top and bottom, moving to the center...

A PBusardo Review - Smoktech RSST Genesis Atomizer - YouTube

It's hard to see, but once the coil has completely oxidized the mesh, it glows from center, out. Normally, when all is working properly, the coil should glow from the center, out. If the leads to the coil are too long, you may see them glow. If the lead does not come off the Deck screw at a good angle to the wick (a direct, touching angle) and has something of a loop in it, it can glow red (this can be seen on the (-) in this video).



The Voltage that the coil will see across it is whatever is actually delivered. In a Mech, there may be a Voltage Drop in the Switch, but whatever Voltage gets past the Switch will be seen across the whole coil. A Mech with a good Switch will have a very small Voltage Drop, to a Zero Voltage Drop in an excellent Mech, so that 4.2V would reach the coil, or close to it. In a VV/VW Mod, the Voltage applied at the 510 is seen across the whole coil, to ground. More specifically, if you connected a fully charged Battery directly to your coil with short non-resistance wires, there would be 4.2V across the whole coil, from (+) to (-), as there would be no other potentials for Voltage Drops.



As a side note:
With Kanthal Resistance Wire, there is a Voltage Drop because of the Resistance of the Wire itself. For example, Kanthal A-1 32g has approx. 0.91 Ohms/inch. The number of wraps determine the Ohms of the Coil. It heats up because it is Heater Element wire. Non-Resistance Wire for normal electrical use has apporx. Zero Ohms, and it is not Heater Wire. Kanthal is designed to Heat Up. So is NiChrome.

Li-Ion Batteries have an Internal Resistance that determines how well they can deliver their Power, and for how long. A brand new Battery can deliver the full 4.2V without much drop in Voltage. As it gets older, it may read 4.2V with No Load, but that Battery's Output Voltage may drop when a load is attached. If it drops by your 0.4V example, then 3.8V will be applied to the coil.