Joules

[Buck]

Electrical/electronic question: Surge protectors are rated in Joules. From my understanding, 1 joule = 1 watt/s, so the surge protector could protect from a 1 second 4200 watt (~38 amps (110V)) surge. Is this a correct understanding?

 

[jtr1962]

That sounds about right. Just be aware that those maximum ratings are misleading since they are usually a one time deal. A 4200 joule rating means it will indeed protect you from a 4200 joule surge-once. After that the surge protector is usually destroyed. However, such large surges are rare, and the surge protector can protect against the more common surges of several joules many times. BTW, the lifetime of these surge protectors isn't culmulative, but heavily related to the magnitude of the surge. For example, if it can protect against a 4200 joule surge once, then it doesn't mean that it can absorb a 420 joule surge ten times, or a 42 joule surge 100 times. Rather, it can absorb lesser surges far more than that. Just as an example, it might be able to absorb a 420 joule surge 25 times, a 42 joule surge 1000 times, and a 4 joule surge 50000 times, etc.

 

[MaxBurn]

I forget exactly what a joule is but those surge supressors certainly don't last forever before they turn into regular power splitters. Much better to have a true on line UPS in my opinion.

 

[timwhit]

Here is a nice power conversion calculator that will show you that 1 joule/second = 1 watt.

 

[CougTek]

IIRC, a joule is the amount of energy needed to move a 1Kg weight on one meter in one second. That won't help you with your power bar, but I was in the mood to post something so...

 

[sechs]

You mean a 1kg mass

 

[CougTek]

There's a difference? In the gym, I lift weights, not mass.

 

[CityK]

Weight v.s Mass

 

[CougTek]

From the wiki, a joule is :

the energy required to lift a small apple (102 g) one metre against Earth's gravity

Then my physic class was way off with its 1Kg weight (or mass, as you wish).

I'll have to calculate the amount of joules I approximately expense at each of my training sessions. It should quite outstanding. No wonder I'm not fat.

 

[LOST6200]

There's a difference? In the gym, I lift weights, not mass.

Treu, but "weightsd" is the correct noun for hte object. The "weights" you lifter have mass.

 

[sechs]

Well... they're also masses. But that makes them sound too heavy to lift.

 

[Stereodude]

Unless I missed something that joules rating is the maximum surge it can take without destroying itself. It will stop stronger surges, but it will sacrifice itself in the process.

 

[Buck]

Unless I missed something that joules rating is the maximum surge it can take without destroying itself. It will stop stronger surges, but it will sacrifice itself in the process.

For a typical surge suppressor, at roughly the quote joule rating, the MOVs burn out, and the over voltage cannot be drained off the line. Thus, the surge now continues forward to the previously protected device.

 

[sechs]

This is to say, it explodes *and* doesn't protect you from a surge.

 

[Explorer]

Then my physic class was way off with its 1Kg weight (or mass, as you wish)...

Kilograms is only mass, not weight. Weight is a force.

The metric mass unit is the kilogram and the metric weight unit is the newton. The metric mass unit WAS the gram, but that was changed a while back to the kilogram. MKS = Metres / Kilograms / Seconds makes up the core of the metric system. From there, all of the other units of measure are derived.

The English (i.e. "American") mass unit is the slug and the weight unit is the pound. Before the advent of the Metric System, most of the world used variations of the English measurement system for weight, mass, volume, the German Fahrenheit scale for temperature, and god knows what for everything else (like the height of a horse or land space, etc).

A stationary kilogram of lead will weigh less on Mars than on Earth, and a stationary kilogram of lead will weigh nearly nothing somewhere in outer space. However, a kilogram of lead will still have the same mass no matter where it is or what it's doing.

Mass accelerated by gravitational force is weight. The acceleration of gravity on the surface of the Earth is 9.81 meters per second (squared). A free-falling kilogram of lead in the Earth's atmosphere weighs... NOTHING! A kilogram of lead sitting stationary on the Earth's surface weighs 9.81 newtons! Flip this around and 1 newton of lead has a mass of 1/9.81 kilograms, or about 0.1 kg.

 

[CougTek]

So if you move 1 newton on 1 meter in 1 second, you've spent a joule, right?

 

[LOST6200]

Geeze, I'm gueesing yuor post gard was not in the physics dept. Listen to Gary and the otehrs.

The bonis qeustion is this: How much does the internaet weigh?

 

[Tannin]

Da Internet? Oh, he ain't heavy, he's my brother.

 

[sechs]

MKS = Metres / Kilograms / Seconds makes up the core of the metric system.

Not quite right. MKS (like CGS) is a convenience system. While the meter, kilogram, second, ampere, Kelvin, mole, and candela are the fundamental units of the SI, there are fields where CGS derived units are commonly used, and a few others where both MKS and CGS are used.

Metric includes all units derived from SI units, including abominations, such as the litre and metric ton (tonne). It is also sometimes inbued with "natural" units like the electron-volt, unified atomic mass unit, and light-year.

 

[Explorer]

So if you move 1 newton on 1 meter in 1 second, you've spent a joule, right?

Well, that sounds right -- the force required (1 Joule) to move a stationary 1 kg mass in a vacuum 1 meter in 1 second in a straight line.

However, for me personally, even though I hardly work directly in Joules, I know that a Joule of energy is 1 amp passing through 1 ohm resistance for 1 second, and that a 1 Watt-Second = 1 Joule (1 Watt = 1 Joule / Second). That's about all I care about when it comes to Joules, specifically. I like Watts.

Not quite right. MKS (like CGS) is a convenience system...

I'm sorry I even mentioned MKS, since I figured someone would want to bring up CGS.

I was taught MKS system when I was a little kiddie. MKS are the sort of units that one deals with in everyday life. CGS system tends to be heavy on itty bitty units for scientists. SI came along about the time when I was in college. About all SI did was incorporate some CGS into the vastly more used MKS. I guess they had to do this to relieve tensions among certain anal retentive academians.

 

[Explorer]

...Well, that sounds right -- the force required (1 Joule) to move a stationary 1 kg mass in a vacuum 1 meter in 1 second in a straight line.

I thinks I was trying to say 0.1 kg of mass above (as in 1/9.81 = about 0.1).


Getting a bit back on topic as far as Surge Protection goes:

You have very brief, short, transitory events to deal with (microseconds, milliseconds, etc) as well as longer events. Each require different forms of protection.

MOVs are usually zinc oxide resistors meant for the short transitory events in lower turn-on voltage ranges -- like a few hundred volts or less. Higher voltages in short transitory events are better handled with voltage suppression devices that uses a mercury vapour in a glass structure that conduct when the line voltage gets high enough (hundreds and thousands of volts).

In both cases, these devices shunt current to earth (ground). They can only handle so much current before they open up (or even explode) and have to be replaced. The little mercury vapour suppressors flash orange light up when they conduct.

 

[sechs]

I guess they had to do this to relieve tensions among certain anal retentive academians.

It really had a lot more to do with confusion than anal rentention.

How many dynes are in a newton? How many ergs in a joule? How many maxwells in a weber? How many gauss in a tesla?