Understanding voltage

Third year. He's specializing by now.

Irrelevant.

It certainly is *EXPECTED* that a Junior in an engineering college knows the rudiments of physics.

Possible, but irrelevant.

Then what, exactly, are you debating?

He's not the "best bridge builder". He's a college student who apparently slept through physics. No, I don't want him building my bridge.

Yes, by the third year he's supposed to have had at least three semesters of physics, one of which should have been E&M.

Ok, I'm not judging him. His college should be boarded up.

You are making a lot of assumptions here from one small post about one thing... You should be ashamed of yourself.

if you picture current as the rate of flow of water in a pipe, voltage is the water pressure.

in the water analogy: Joules / Cubic meter IOW: pascals

it has it by being displaced by a from where it would like to rest the further it is displaced the higher the voltage.

different pressures, with 10kPa you can spin a turbine nicely, but same flow rate with only 10Pa behind can do very little work.

Bye. Jasen

Unfortunately sometimes it does.

Early versions of one popular M68K based machine (I forget which) had a bug that was helped by moving the mouse which generated extra interruots and sped things up.

Bye. Jasen

Bridges are civil engineering aren't they?

Why? He's a third year engineering student that has zero clue about a rather important aspect of physics that he *SHOULD* have covered. It is the equivalent of my not knowing what mechanical force was when I was a college junior. Somebody failed miserably here.

Some are rocks--like the Wheatstone Bridge.

Bill

That's making it too bloody complicated. Absolutely basic that: Voltage (Or EMF, electro motive force, or potential or whatever you want to call it) is the pressure that can push an electric current through a circuit. The source of the voltage can be various devices, such as a battery, a generator or a storage device such as capacitor. 'Voltages' can be DC (Direct current) or AC (Alternating current). Take a pencil and draw a square to represent 'the source'. Then draw a circuit from and external to the source comprising wires (which have virtually no resistance in most practical applications) and a load (which could be say a single heating resistor of R ohms). Electric current (amps) will flow in the above circuit. The higher the voltage the greater the current that will traverse the circuit. The formula; Ohm's Law is Voltage/Circuit Resistance =3D Current flow. A practical example being 230 volts, a 20 ohm resistor, and a resulting current flow of 230/20 =3D 11.5 amps If you want to get into the amount of power (watts, or watts per hour) how many coulombs of energy are being transferred you can make further calculations. But the above is basic. PS. Working in telecommunications for some 40 years we once had a boss who was an 'Industrial Engineer'. We (experienced subordinates) always gave him a hard time saying "Well who can expect an Industrial Engineer to understand electricity with more than one frequency!" So congratulations to the OP on wanting to understand electricity.

There's a fascinating bit of philosophy hidden in this inquiry. Voltage and charge are two completely different kinds of physical quantities, and the distinction between these is repeated in many different ways over all disciplines (which is why so many analogies are offered when the question comes up).

Voltage is an example of an intensive quantity. Charge is an example of an extensive quantity. If you consider a system (like, let's take a battery/bulb flashlight), the voltage of that battery is an intensive quantity, and the charge that the battery can deliver is an extensive quantity. Double the flashlight, and there are two batteries and two bulbs,twice the charge, but the voltage is the same. Double the dimensions of the flashlight, the bigger battery has eight times the charge, but the voltage is STILL the same.

Extensive quantities include mass, charge, cost of a bag of potatoes. Intensive quantities include density, voltage, cost per pound of potatoes.

Voltage, in particular, is the ratio of two extensive quantities, stored electrical energy and stored electric charge, in the sense of taking a derivative of energy with respect to charge. Just like the cost per pound of potatoes, it's intensive.

The implications of this include another check you can perform on equations: you can't add or equate intensive and extensive quantities, just like quantities with different units.

Congrats.. Somebody got it right. Why didn't someone tell him to understand Ohm's law?

---------------------- But it isn't right and saying it is right doesn't help.

Although this analogy is valid and can be worked out mathematically, it is the dual (in the circuit sense) of the analogy that is usually used.

Mechanical Electrical Force Voltage Speed Current Mass Inductance Compliance Capacitance Windage Resistance Sliding friction is very different

This is the scheme used mostly by Olson. some of the analogous equations are: f=ma v=L(di/dt) P=fs P=ei s is used for speed KE=m*s^2/2 KE=L*i^2/2 magentic energy in an inductor.

This also leads to one of the most useful analogies that I have used--impedance, especially characteristic impedance. For ac quantities. Mechanical impedance = f/s and and Z=v/i. This concept is good for levers, loudspeakers, gearboxes, transformers, etc.

Bill

You're un-civil.

Well, your post was un-civil engineering, anyway. :-)

Howard Hughes proved that liquids are compressible.

Then, we all called him a genius, which he was.

Then, he crashed his toy (or it was sabotaged). Then, he went nuts.

You must have missed where he DID mention velocity.

I don't remember. Maybe I was thinking of the Whitestone Bridge.

Bill

Don't feed the dimbulb troll

Right. Prior to that, nobody noticed that sound propagates in water.

C'mon Roy, explain voltage to us.

John