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> The mystery is in saying that there is actually "no voltage", and the
> current is just magically flowing all by itself.
Well, the quick way to explain is to look up the formula for an inductor:
V(t) = L * dI / dt
So, the voltage is proportional to the rate of change of current. This is
because a magnetic field is generated by the flowing current, and when the
current changes the magnetic field generates a reverse-voltage to try and
cancel out the current change.
Nowhere does it say that a voltage of zero means no current flows.
If you've got 5 V and 5 A flowing through an inductor and you then suddenly
switch the current to 10 A, it's quite possible that the inductor will
generate a back-emf of -5V (so giving a sum of zero across the inductor) to
try and keep the current at 5A. During the split second that the voltage is
zero, it is behaving exactly like a piece of wire with no resistance.
Or for a capacitor:
I(t) = C * dV / dt
This says that the current is proportional to the rate of change of voltage.
Nowhere does it say that no current can flow if the voltage is zero. But,
note, the rate of change of voltage can't be zero, otherwise no current
would flow.
But for a resistor:
V(t) = I(t) * R
In this case, I=0 means V=0 whatever is going on (for non-zero R)
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Am Wed, 02 Apr 2008 13:19:09 +0100 schrieb Stephen:
>
> As an engineer I agree, so it must be true :) Does an electron have less
> energy in a circular path than a straight one. You are pumping energy
> into the system so I would have thought that it would be a gain in
> energy for the electron and a loss of energy to the magnetic field.
No. If there was no such thing as "synchrotron radiation", the electrons
would neither gain nor lose energy in a circlular path, not different
from a stone tied to a teather and swung around in a circle (neglecting
the friction forces for a moment) or the earth orbiting the sun.
BUT, we have syncrotron radiation, so after one traverse of the storage
ring, the electrons have a little less energy than before. To maintain a
steady operation, the lost (or better: transferred to the experiment
hall) energy must be given back to the electrons, and that's why in the
storage ring there's a acceleration section (this time truly tangential)
which adds energy to the travelling electrons (exactly the amount emitted
by the radiation).
> BTW I also have problems with credit and debit when working on financial
> systems ;)
Well, as long as you know which one must be on your account... ;)
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Stephen wrote:
> BTW I also have problems with credit and debit when working on
> financial systems ;)
Double entry book keeping FTW! :-D
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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On Wed, 02 Apr 2008 14:00:00 +0100, Invisible <voi### [at] dev null> wrote:
>Stephen wrote:
>
>> BTW I also have problems with credit and debit when working on
>> financial systems ;)
>
>Double entry book keeping FTW! :-D
Aye! WTF :) I understand it but the terms are reversed. For instance,
out is crediting. This is because (so I've been told) that it is from
the "bank's" point of view. Go figure why that is useful :)
--
Regards
Stephen
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>> Double entry book keeping FTW! :-D
>
> Aye! WTF :) I understand it but the terms are reversed. For instance,
> out is crediting. This is because (so I've been told) that it is from
> the "bank's" point of view. Go figure why that is useful :)
It's quite simple. All money comes *from* somewhere, and goes *to*
somewhere else. Conservation of finance! :-D
The part I can't figure out is how you do the accounts of a company, and
they end up with more money than they started out with, even though it
hasn't apparently "come" from anywhere... Accounting is weird!
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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>> This explains why on old cars the radio switches off momentarily as you
>> start your car.
>
> What do you mean "old cars"?
On most new cars the entertainment system must function correctly for supply
voltages over a very wide range, like down to 6 or even 4 volts, and up to
16 or 18 volts. This means that the radio (and all the other stuff like
satnav, climate control display etc) won't turn off while you start the car.
In the past the radio wasn't specced this high, and it was ok to only work
down to say 10 volts. Of course this meant that when you started the
engine, the voltage dropped down to 6 or so volts and the radio turned off.
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Stephen wrote:
> On Wed, 02 Apr 2008 14:00:00 +0100, Invisible <voi### [at] devnull> wrote:
>
>> Stephen wrote:
>>
>>> BTW I also have problems with credit and debit when working on
>>> financial systems ;)
>> Double entry book keeping FTW! :-D
>
> Aye! WTF :) I understand it but the terms are reversed. For instance,
> out is crediting. This is because (so I've been told) that it is from
> the "bank's" point of view. Go figure why that is useful :)
you have increased their debt to you. Simple innit (as they say here)
John
--
I will be brief but not nearly so brief as Salvador Dali, who gave the
world's shortest speech. He said, "I will be so brief I am already
finished," then he sat down.
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On 2 Apr 2008 07:57:14 -0500, Michael Zier <mic### [at] mirizide> wrote:
>No. If there was no such thing as "synchrotron radiation"
Nope! I'm not going down that road. Ultrarelativistic particles, I'll
stick to Newton thank you very much :)
--
Regards
Stephen
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On Wed, 02 Apr 2008 15:07:30 +0100, Doctor John <doc### [at] gmailcom>
wrote:
>Simple innit (as they say here)
Yeh! But try explaining that to a hairy (something-ed) engineer who
doesn't want to put your system in, in the first place :)
--
Regards
Stephen
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scott wrote:
>>> This explains why on old cars the radio switches off momentarily as
>>> you start your car.
>>
>> What do you mean "old cars"?
>
> On most new cars the entertainment system must function correctly for
> supply voltages over a very wide range, like down to 6 or even 4 volts,
> and up to 16 or 18 volts. This means that the radio (and all the other
> stuff like satnav, climate control display etc) won't turn off while you
> start the car.
>
> In the past the radio wasn't specced this high, and it was ok to only
> work down to say 10 volts. Of course this meant that when you started
> the engine, the voltage dropped down to 6 or so volts and the radio
> turned off.
Interesting. I've never seen any car where turning the ignition
*doesn't* disable all the other electrics in the system [including the
headlights].
As I understand it, turning the starter motor requires a massive amount
of current, and is essentially the *only* reason a car has such a
whopping great battery in the first place. (Certainly it's not necessary
just to run the spark plugs... or even the headlights...)
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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