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I'm looking for an explanation of voltage that doesn't compare electricity to water and voltage to pressure?
A while back I started self-studying electricity and several sources explained voltage as being like water pressure. I remember that there were lots of situations that made no sense to me and I was going nuts until I consulted a friend who is a physics buff. It became clear that the reason I couldn't understand electricity is that I was thinking of voltage as pressure which is actually a terrible analogy that doesn't fit at all.
I would like to get back into learning about electricity, so I'm hoping someone could point me to a book, website, or something that explains voltage without claiming it's like pressure. Thanks!
4 Answers
- Anonymous1 decade agoFavorite Answer
Voltage is a measure of the amount of energy that each electron has. More specifically, it is the difference in that energy between two points in a circuit.
The unit of EMF is the "volt", which is defined as one Joule of energy per Coulomb of electrons.
A 9V battery gives 9 Joules of energy to every Coulomb that passes through it, and pushes them toward the negative terminal. A resistor that has 5V being dropped across it means that each Coulomb that passes through it loses 5 Joules of energy (usually to heat).
In layman's terms, voltage is a measure of how much "kick" each electron has when going through the circuit. Higher voltages mean that each electron is much more lively and energetic, and can do more work, than lower voltage ones do.
It's in this sense that voltage is compared to pressure. Voltage is the force that compels electrons to move through a circuit, and pressure is the force that compels water to move through a pipe.
Source(s): Electric Circuits Fundamentals textbook - oldprofLv 71 decade ago
I = V/R; where I is current, V is voltage, and R is resistance.
a = F/m; where a is acceleration, F is force, and m is mass.
And there you are. Think of voltage as the force (not pressure) that pushes those electrons along against some resistance to their moving. mass m is like the resistance R in that mass represents inertia which is a resistance to change in velocity, which is acceleration. And if you think of force as a push or a pull, then voltage is a push or pull on electrons.
In physics lab, we used to use I = V/R on analog computers to model a = F/m. So for a given V, say, 10 v that would represent say 10 Newtons of force. And R in ohms would be varied with 1 ohm per kg. The result in amperes would represent the acceleration which would graph out against the varying ohm as mass.
- Randy PLv 71 decade ago
I think of voltage as height, and the analogy works extremely well. That is because the form of the gravitational force F = Gm1 m2/r^2 and the electrical force F = k q1 q2/r^2 are very similar.
So long as you remember that unlike gravity, in electricity there are negative charges (things that like to roll uphill), that works fine.
I know why they use the water pressure analogy. It's so that you have an analogy for resistors in terms of narrowness of pipes. Put resistors in parallel and the pipe is wider. There's less resistance.
I don't have a good resistor analogy for when I think in terms of height and balls rolling downhill. Unless you want to keep thinking about a pipe, but this time a pipe full of junk, so there is "resistance" as the ball rolls downhill through the pipe. Wider pipe, less resistance. That is in fact what happens to electrons inside resistors.
- Old Science GuyLv 71 decade ago
voltage is a measure of potential energy per unit of charge
if it takes 1 J of work to move 1 C of charge from one place to another
then
the 1 C of charge has acquired 1 volt of potential in the move
and
the two places have a potential difference of 1 volt
a volt being defined as a Joule per Coulomb
take gravitational potential as an analogy
if a table is 1 m high and a chair is 0.5 m to the seat
then moving a mass of 1 kg from the seat to the table top takes mgh work
or 1(9.8)(0.5) = 4.9 J
so the change in potential is 4.9 J
now
since we raised 1 kg we could talk about the potential difference between the seat and the table in terms of energy per kg
in this case 4.9 J / 1 kg or 4.9 J/kg
we could now use this ratio to find out how much work it would take to lift 4.5 kg from the seat to the table
4.5 kg * 4.9 J/kg = 22.05 J
thinking of volts as a measure of 'energy density' may help
a potential difference of 1 million volts is scary and rightly so
but
if only 1 millionth of a Coulomb moves across this potential difference
then only 1 J of work is done - not a big deal
however
if just 1 Coulomb moves across
then 1 million J of work is done - really big deal
hope I didn't just add to your confusion