I would add, voltage is directly related to the arc length in processes
such as GTAW, SMAW, GMAW. As the GTA torch is pulled further from the
workpiece, the voltage goes up.
In arc welding, current is adjusted for the disired weld size and metal
thickness. Thicker metal and larger welds require more current to melt
"ben carter" wrote: Anybody got a clear way to explain to an educationally
diverse group of students how amps and volts are different in arc welding ?
Are you trying to explain what volts and amps have to do with arc welding,
or are you just trying to explain the way current flows in a circuit as a
result of voltage difference?
Ayup..thats the one I use too.
"If I'm going to reach out to the the Democrats then I need a third
hand.There's no way I'm letting go of my wallet or my gun while they're
"Democrat. In the dictionary it's right after demobilize and right
before demode` (out of fashion).
-Buddy Jordan 2001
Suggest you research (Google or otherwise) drooping generators, drooping
volt amp curves, CC (constant current), desired volt amp curves for SMAW vs
GMAW, CV constant voltage, also effect of arc length on drooping volt amp
curve power generator or welding power source.
A good way to explain the concept is with a good illustration of a volt amp
curve as produced by a drooping welding power source. The best will be to
obtain power curves for all the ranges of a classic Lincoln type DC
generator and demonstrate how the arc characteristics will differ for a
similar heat setting on separate ranges. This can lead into a discussion of
the whipping technique used to make a root pass in pipe with 6010.
First off, I'm an electronics engineer and not a welder. I also don't
know if the following explanation is any clearer than anyone else's.
But I know that welding requires heat. Heat represents power
dissipation in the metals. This heat has to come from the
Power is amps times voltage (P=I*E) in electrical circuits. To
increase the power (heat), you either have to increase either the amps
or the voltage. Either will do, but high voltage can kill you, so
welding is usually done with low voltage and high current (amps).
The reason high voltage kills is that it can overcome the resistance
of the skin and conduct current through your body - enough to stop
your heart maybe. There's a whole lesson here someplace on safety and
watching out for 110/220v from the line. It's ac, but it's high
enough voltage to perhaps cause damage.
Voltage can be used to model water pressure. Think of the high
pressure coming into your house. Resistance to water flow can be
modeled by an electrical resistor or throttling device (hose bib).
This is why having too long a delivery wire to the work can cause
problems. It has too much distributed resistance that will cause a
voltage drop at the weld, much like having a really long hose or a
hose with a kink in it will drop water pressure.
Amperage can be modeled by water flow. A large diameter hose can
carry more water per minute than a small diameter hose can at the same
pressure difference. So amps are essentially gallons per minute in
the analogy. A large diameter wire will have less resistance than a
small diameter wire, so welding cable has a large diameter to reduce
This is probably not as clear as you'd like, but I'm old and it's late
It seems to me that what is really of interest and use would be
understanding from a use point of view. What happens to a weld when you
use the wrong type power supply (what does the right one do for the
arc)? Why is the type of power supply different for different welding
processes? This is the sort of understanding that I suspect would be
Spend a couple of minutes on the water analogy to start, then get to the
real point of the talk. I really dislike the water analogy, but I don't
know of a better one. The problem is that electricity is so
abstract--unlike water, for instance.
"Steve Smith" wrote: (clip) The problem is that electricity is so
abstract--unlike water, for instance.
That is exactly why the water analogy works so well--anyone can visualize
it. A gallon of water is a coulomb. A gallon per second is an amp. PSI
translates into volts. Small pipes or long pipes have more "ohms." It
I agree with "the water analogy" for explaining electicity, to answer
Ben's question - current is like how much flow of water there is and
voltage is like what pressure it is under. I teach in a technical
college and I know this explanation would work just fine with your
I had my own separate interest in this statement:
"This can lead into a discussion of the whipping technique used to
make a root pass in pipe with 6010."
My question - are you doing something to the arc volts and therefore
heat input when you are whipping the rod?
I am new to this group and am not a tech school instructor so am hesitant to
be too opinionated on the subject of teaching because I have little
experience with what works as explanation to varying levels of background
and knowledge. As a general and personal opinion, I am usually opposed to
the search for excessive analogy to describe physics. IMHO the actual
science makes more sense to me than stretched comparisons or forced analogy.
I am certainly opposed to the current drive to dumb everything down to the
point of insult. I think we need to challenge ourselves to rise to the real
I took my own advice and searched on my suggested key words
came up with a couple of decent hits that led to more good stuff. I
suspect that a more refined search will give even better results.
looks like a good link regarding SMAW and is not really what we are
looking for but it reminded me that Lincoln Electric was the source of some
of the best books in my welding library. I went to their website
with high expectations and soon found this
like there is plenty here to keep anyone busy for a while. I found this
list of available books,
prices are higher than I remember but still very reasonable. This has
always been one of my favorites
Google also turned up this which is very close to what I was looking for
10-2 it discusses drooping power sources and arc length in detail. I failed
to find an index page for this book but it seems to start at
I think you
will notice the combination to get the rest of the chapters but be careful
as there are popups that may be dangerous.
You may draw your student's attention to the difference between a welding
generator and one which is designed for pipe thawing (very low open circuit
voltage, high closed circuit amperage and 100 % duty cycle) which is a task
that has killed many good welding machines. This will probably lead to a
discussion of power, watts, ohms law and duty cycle.
This is opening a big door and I do not know where to start. Section 10-2
of this link
is a good start but is not the last word. Basically lengthening the arc
causes the voltage to rise and the amperage to drop, (drooping power source)
this reduces the burn off and deposition rates and can help to open up the
key hole. Whipping the arc out of the puddle can allow it to fast freeze
and permits us to lay the metal into the groove in the regular ripples that
give 10 (and 11) welds their distinctive appearance. Shortening the arc
raises the amperage and the burn off and deposition rates and fills the
puddle. Whipping too far can remove the shielding gases and cause problems
(and is not a good technique for low hydrogen rods which require a more
subtle touch and respond more to rod angle and travel speed).
I am sure you have noticed that when welding overhead it is often helpful to
turn up the heat and shorten the arc in order to soften the arc and stop the
puddle from falling. With a dual control generator (like a Lincoln 300) we
can raise the left (range) control and lower the right (voltage) control to
give a softer arc and to change the slope of the drooping volt anp curve.
This description is not as concise as it should be. I am sure that a little
prospecting on the web will find many better.
You don't really need to understand volts and amps to weld - just their
combined power is an adequate concept, so long as you _do_ get across
the notions of "constant" and "drooping" curves. If you communicate
that "manual processes vary power with length, so you have control" and
"wire-feed processes are self-regulating, no matter what the stick-out",
then you've got the crucial part across.
I was an Electronic Tecnologist for our National Broadcaster( CBC) in
Canada. I taught Basic Electronics in l Night School at our local High
School as a hobby.
When I retired I took 2 years of Welding training, got some tickets
and went to work with the Local Boilermakers.
I have been reading the posts with intrest and I must say there are
quiite a few opinions on the subject.
We must not forget that welding students don't care if the resistance
of the rod is .1 ohm or 5 megohms. or what the particular voltage at
the weldement is.
They want to make good welds and pass the course.
Water is an excellent comparison to electricity. Always has been and
always will be.
Unless the Politicians repeal Ohms Law!!!
Anyway that's my story keep up the good work....
Current - think electrons/time
Voltage is the pressure - think of pressure that drives the electrons.
Given a resistance, as the voltage increases so does the current.
If one has a constant voltage machine that might have high voltage surges to arc
through thin films and the current setting determines the electrons/time or
consider the heat. More current - more heat.
Voltage allows current to flow across a gap - the higher voltage the wider the
Lightening itself is very high voltage - jumps a wide gap from cloud to tree and
- read that AND
very high current - the bolt is white hot and wide - vaporizes the sap and water
in the tree -
When there is current flowing, there is power.
Power = voltage * current. If one varies the current and maintains the voltage
(because the machine does)
one varies the power. More power more heat more melt more penetration and so
Martin A physicist wearing a different hat.
Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member