ohms

[trip-wire]

could sumone plz expain ohms to me

[Corn-Picker]

Ohms are a measurement of resistance. Resistance is a positive number. Resistance is a property of the material conducting the electricity. If a wire with electriciy flowing through it were a pipe with water flowing through it, resistance would be analagous to friction.

Just like in a pipe, if you increase friction while keeping pressure constant, flow rate will decrease. In a wire, if you increase resistance while keeping potential constant, current will decrease.

I had a lot of my college training in fluid dynamics. There is a very powerful analogy between flow of fluid though a pipe and flow of electricity through a wire. Think of pressure as potential (voltage), flow rate as current (amps), and friction factors as resistance (ohms).

[trip-wire]

so for example maybe 16 ohm outputs would be too much for 8 ohm speakers????

[Corn-Picker]

Originally posted by trip-wire
so for example maybe 16 ohm outputs would be too much for 8 ohm speakers????

I'm sure someone on this board can answer your question, but I can't. I don't know much about electricity and circuit design yet, I just have a few equations memorized that I can relate to my chemical engineering background.

V = IR is the secret to being an electrical engineer
The sum of the forces = 0 is the trick for civil engineers
In = Out is great for us chemical engineers
And I still havne't figured out what the heck industrial engineers do

[MRehorst]

Now could someone please explain to me why units are named after people?

One Newton is equivalent to 1 kg m /s^2. Many calculations are simplified and made clear when the no-name units are used. Why is it necessary to confuse the issue and the calculations with a person's name?

One that really bugs me is Ohm and Siemen. The same thing inverted gets another guys's name? In that case, I propose, nay demand that 1/1V from now on be referred to as a "Rehorst". You have my permission to use "R" for the abbreviation. If that is already taken by some physical constant, I'm amenable to working out another abbreviation, just as long as it always refers to a unit with MY name.

MR

[Nelson Pass]

The units are named after the people who worked this
stuff out. Seems like the least we can do.

[halojoy]

Originally posted by trip-wire
so for example maybe 16 ohm outputs would be too much for 8 ohm speakers????

You could use 2x8ohms speakers
That is connect two 8-ohms speakers in serries
to the 16 ohms output jack.

It is best not put speakers lower than 16 ohms
in that output.
To put speakers higher than 16 ohms is not as bad.

The lower ohms - impedance a speaker have,
the more current it need from the amplifier.

An 4 ohms takes twice as much current as an 8 othms,
at same Volume setting.
It can be too much, get hot, and amplifier fuses burn.
Or amplifier transistors burns, which is worse.

/halo - don't like his fingers burned

[Circlotron]

Originally posted by trip-wire
so for example maybe 16 ohm outputs would be too much for 8 ohm speakers????

8 ohm speakers don't have enough resistance for a 16 ohm output, so too much current would flow from the amplifier through the speaker (actually double) and you may upset your amplifier. The lower the resistance, the more it is like a short circuit. Zero ohms is a short.

[GRollins]

16 ohm outputs?
A tube amp, perhaps?
It'll work. Depending on the design of the amp, it will probably have slightly higher distortion, but it won't be obnoxious.
One of the classic things to do with a tube amp is to try your speakers on different impedance taps. The sound changes a bit--not much--but perhaps enough to put you in a better position, sound-wise.
Note that if this is, indeed, a tube amp, it will not double power into a lower Z load (going from 16 to 8 ohms) in the same manner that a solid state amp would. In fact, power will probably be slightly less.

Grey

[haldor]

Originally posted by Corn-Picker
V = IR is the secret to being an electrical engineer

Only for a purely resistive impedance, otherwise you have to include some cos(wt) terms to muddy the waters.

Here a link that explains it just like I learned it in school.
http://iml.umkc.edu/physics/wrobel/PHY250/lecture4.pdf

The sum of the forces = 0 is the trick for civil engineers

That works for electrical too, the sum of the currents into and out of a node is always = 0 (Kirchoff is never wrong).

About the unit naming business. Do something as wonderful and ground breaking as those guys did and something will get named after you. Makes you wonder about the justice of it sometimes though. Darwin did some good science, surely he deserved something better than the Darwin Awards.

Phil