magnetic field

[Don Kelly]

--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer
"qude" <qmdynamics@yahoo.com> wrote in message
news:1119216943.195356.8180@g44g2000cwa.googlegroups.com...

right?

This means the 12volts/18ampere setup produce larger
magnetic field magnitude (from the current flow) than
the 110volts/2Ampere setup (noting that both produce the
same 220 Watts power), right??

Or does the larger 110 volts in the latter give more push
to the 2 ampere resulting in similar magnetic field
magnitude for both setups??

If the answer is that the 12volts/18 ampere indeed
produce larger magnetic field, do designers find it
necessary to use larger voltage instead of larger
current to prevent magnetic field interference?

If the answer is that both produce the same magnetic
field magnitude, then it means in larger voltage
such as 110 volts, it pushes the 2 ampere more so
it moves faster compared to the 18Ampere with 12
volts that don't push it faster. If not, how can
the magnetic field magnitude in both be the same
(assuming they are the same).

Thanks.

qude
---------

Who were you answering? There is no indication of what you are saying
"right" to. Please include at least some of the material you are responding
to.

The magnetic flux density due to a wire carrying current I is proportional
to the current and inversely proportional to distance. The presence of other
current carrying wires (such as the necessary return path(s) affect the flux
density so consideration of a single wire in space is not a realistic
option(effectively you have a single turn coil with a return conductor
infinitely far away).
The field due to a current of 2A is 1/9 that due to a current of 18A at a
point external to the wire.

Is this of importance to decisions as to what voltage is to be used? Not
really.

There is an optimum voltage level depending on the power to be transferred
and the distance it is to be transferred (at a given frequency). Rule of
thumb- more power and or longer distance- go to higher voltage. This is not
a physical rule- but an economic one. That is why AC transmission put
Edison's DC systems out of business. You can transmit 100MW at 200V for a
distance of 200 miles but the cost would be horrendous compared to doing it
at 140,000V. However, to use 140,000 V to supply a home would be rather
dangerous, expensive, and ridiculous so 120/240 is a good practical and
economic balance. (Sue, you should know this- examples are all around )
--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer

 

[Don Kelly]

Related to Lenz' Law- yes. Related to conservation of energy- also true.
The aluminum plate is essentially the secondary of a transformer (not a good
one by any means).
Look up transformer operation as well as the background for the expression
Erms =4.44FN(flux maximum) for sinusoidal AC.
--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer

"qude" <qmdynamics@yahoo.com> wrote in message
news:1119330643.140180.186910@f14g2000cwb.googlegroups.com...

Dave wrote:
"qude" <qmdynamics@yahoo.com> wrote in message
news:1119273009.300137.199390@z14g2000cwz.googlegroups.com...


CWatters wrote:
"qude" <qmdynamics@yahoo.com> wrote in message
news:1119223515.039007.79790@g47g2000cwa.googlegroups.com...


Suppose you have a current source with magnetic field
and you want to reduce it by adding a metal near it
to induce opposite magnetic field to cancel the one
from the source (partially). What coil configuration
must you use? Is this possible?

All electrical circuits have a return path. The best you can do is to
use
a
second wire for the return path and to twist it around the signal
wire.
You
now have equal currents flowing in opposite directions in close
proximity.
The magnetic fields almost cancel out.

I'm asking whether putting a separate wire without voltage or
current source with certain coil configuration can cause
opposite magnetic field to be produced by the induced current,
and what is the magnitude of it, Anyone knows?

qude


yes it can. magnitude depends on configuration and incident field.
i.e. a
plate of aluminum can almost completely cancel a 60hz magnetic field due
to
induced currents.


To avoid confusion.

This is what I'm describing. A plate of aluminium put over a wire
carrying 60 hz AC or fluctuating dc. Using the right hand rule,
the current is clockwise looking from the source at the left. Now
what I wanna understand is how does the induced current in
the plate of aluminum (not in contact with it but put on top of
it at a distance) produce magnetic vector that is in opposite to
that of the wire. Does this something to do with Lenz law?
What's the proof that induced current and magnetic field
in the aluminum plate is opposite to that of the wire... which
part of the plate the current flows?

Thanks guys.

qude

 

[Gerald Robinson]

"Dave" <noone@nowhere.com> wrote in message
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"Gerald Robinson" <gerald@robinson5333.freeserve.co.uk> wrote in message
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"Dave" <noone@nowhere.com> wrote in message
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"qude" <qmdynamics@yahoo.com> wrote in message
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Dave wrote:
"qude" <qmdynamics@yahoo.com> wrote in message
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CWatters wrote:
"qude" <qmdynamics@yahoo.com> wrote in message
news:1119223515.039007.79790@g47g2000cwa.googlegroups.com...


Suppose you have a current source with magnetic field
and you want to reduce it by adding a metal near it
to induce opposite magnetic field to cancel the one
from the source (partially). What coil configuration
must you use? Is this possible?

All electrical circuits have a return path. The best you can do is
to use
a
second wire for the return path and to twist it around the signal
wire.
You
now have equal currents flowing in opposite directions in close
proximity.
The magnetic fields almost cancel out.

I'm asking whether putting a separate wire without voltage or
current source with certain coil configuration can cause
opposite magnetic field to be produced by the induced current,
and what is the magnitude of it, Anyone knows?

qude


yes it can. magnitude depends on configuration and incident field.
i.e. a
plate of aluminum can almost completely cancel a 60hz magnetic field
due to
induced currents.

Is it always cancellation.. or can you make the configuration such
that the induced field would add up to the source increasing
the magnetic field (or does the law of conservation of field
applies here).

qude
in antenna design you can configure conductors to increase the field in
one direction but it always is decreased in some other direction because
of conservation of energy. i haven't really thought of that for low
frequency work, but would assume the same would apply, while reducing
the field by cancellation is one direction it must increase in some
other area, minus a bit for losses from resistive heating in the
material used for the shielding.



How would you calculate the losses?

very carefully. calculating induced currents and losses is not the
easiest problem, especially in solid plates. it may be a bit easier in
wire loops.


In an earlier question I am asking about using the heating effect?

yes, if a current is induced by the magnetic field then there will be some
loss due to heating in the material.


How would you maximise the heating effect?

 

[Dave]

"Gerald Robinson" <gerald@robinson5333.freeserve.co.uk> wrote in message
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"Dave" <noone@nowhere.com> wrote in message
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"Gerald Robinson" <gerald@robinson5333.freeserve.co.uk> wrote in message
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"Dave" <noone@nowhere.com> wrote in message
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"qude" <qmdynamics@yahoo.com> wrote in message
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Dave wrote:
"qude" <qmdynamics@yahoo.com> wrote in message
news:1119273009.300137.199390@z14g2000cwz.googlegroups.com...


CWatters wrote:
"qude" <qmdynamics@yahoo.com> wrote in message
news:1119223515.039007.79790@g47g2000cwa.googlegroups.com...


Suppose you have a current source with magnetic field
and you want to reduce it by adding a metal near it
to induce opposite magnetic field to cancel the one
from the source (partially). What coil configuration
must you use? Is this possible?

All electrical circuits have a return path. The best you can do is
to use
a
second wire for the return path and to twist it around the signal
wire.
You
now have equal currents flowing in opposite directions in close
proximity.
The magnetic fields almost cancel out.

I'm asking whether putting a separate wire without voltage or
current source with certain coil configuration can cause
opposite magnetic field to be produced by the induced current,
and what is the magnitude of it, Anyone knows?

qude


yes it can. magnitude depends on configuration and incident field.
i.e. a
plate of aluminum can almost completely cancel a 60hz magnetic field
due to
induced currents.

Is it always cancellation.. or can you make the configuration such
that the induced field would add up to the source increasing
the magnetic field (or does the law of conservation of field
applies here).

qude
in antenna design you can configure conductors to increase the field in
one direction but it always is decreased in some other direction
because of conservation of energy. i haven't really thought of that
for low frequency work, but would assume the same would apply, while
reducing the field by cancellation is one direction it must increase in
some other area, minus a bit for losses from resistive heating in the
material used for the shielding.



How would you calculate the losses?

very carefully. calculating induced currents and losses is not the
easiest problem, especially in solid plates. it may be a bit easier in
wire loops.


In an earlier question I am asking about using the heating effect?

yes, if a current is induced by the magnetic field then there will be
some loss due to heating in the material.


How would you maximise the heating effect?


study electromagnetics for a few years so i knew how to model the eddy

currents at different frequencies and field strengs, then some material
science to learn about the different types of materials and their
properties, then probably some thermodynamics thrown in because the flow of
the heat once its induced in the material will affect it also. then i would
figure out the best frequency and field strength to heat whatever the
specific material was that i was working with.

 

[CWatters]

"bryant" <hawkesasc@aol.com> wrote in message
news:1119886529.471672.182130@f14g2000cwb.googlegroups.com...

Ron-

The 2N5809 is a small signal plastic case low noise, hi gain transistor
typically by Motorola used for audio applications. I used these in the
early 70's with good success. As I recall, hfe is on the order of 250,
Vce about 30v. I may have one or two left.

According the to the Mil spec I posted types 2N5806 to 2N5809 are "Silicon
bi-directional triode thyristor" with voltage ratings of 200-600V

 

[Dave]

"emma" <mrandmrsrelativity@yahoo.com> wrote in message
news:1119905485.420796.301280@o13g2000cwo.googlegroups.com...

To create source of magnetic field. You only need wires as
the current passing thru them can create it. The electric
field in the wires is null because there is a cancellation
inside the positive lattice and electrons.

I'd like to build a very strong source of electric field
only. Can I use two big kitchen plates and connect each
of them to positive and negative of a car battery? Would
this create electric field in the middle.

yes

Pls. mention all sources that produce electric fields
with minimal magnetic field present. Beside the
capacitor concept. How else could you creates source
of electric field where the electrons charge become
bare and no cancellation from the atomic lattice.

the most obvious ones are van de graff generators that can create very large
fields with a tiny current by moving electrons from one electrode to the
other.

Does this mean there are positive and negative sources
of electric field that can be built using circuits.
For example, if you force out electrons from a certain
material, does it produce a positive electric field
from the positive ions left? What materials can do
this?

sure, any circuit that moves electrons creates an electric field. however
if you start with neutral matter you end up with symmetric positive and
negative charges, you can only separate them not create them separately.
any material can do this, its just easier with some than others and it
depends on what you are trying to do.

 

[Uncle Al]

emma wrote:

To create source of magnetic field. You only need wires as
the current passing thru them can create it. The electric
field in the wires is null because there is a cancellation
inside the positive lattice and electrons.

Rub your feet on the carpet during a dry day.

I'd like to build a very strong source of electric field
only.

van de Graff generator (DC continuous). Wimshurst generator (DC
continuous or pulsed). Marx generator (DC pulsed). Tesla coil (kHz
AC). Snap together 100 transistor batteries in a row - that's 900 V
end to end (DC continuous).

Can I use two big kitchen plates and connect each
of them to positive and negative of a car battery? Would
this create electric field in the middle.

Sure, 12 whole volts, except for the plates. 12 V can kill you.

Pls. mention all sources that produce electric fields
with minimal magnetic field present. Beside the
capacitor concept. How else could you creates source
of electric field where the electrons charge become
bare and no cancellation from the atomic lattice.

Rub your feet on the carpet during a dry day.

Does this mean there are positive and negative sources
of electric field that can be built using circuits.
For example, if you force out electrons from a certain
material, does it produce a positive electric field
from the positive ions left? What materials can do

You shouldn't be trusted with anything electrical until you have
something useful between your ears.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf

 

[CWatters]

"emma" <mrandmrsrelativity@yahoo.com> wrote in message
news:1119929531.430179.11100@o13g2000cwo.googlegroups.com...

In an Alternating Current system, the electrons oscillates back
and forth. In Power Inverters (where you convert DC to 110
volts AC), the output is just a sine wave.. meaning the
electrons don't really oscillate back and forth but only vary
in intensity in time. What is the effect of either on the load? Are
their Power Inverters where the electrons can also
oscillates back and forth like in the AC?

I think for your purposes you can assume there is no real difference between
the AC you get from a wall socket and that produced by a mains inverter. The
electrons behave similarly for both.

Some mains inverters don't produce very pure (smooth) sine waves and that
can cause problems for sensitive equipment like radios.

 

[JANA]

Why not get a DC volt meter, and have an accurate reading?

A dedicated AC volt meter was not designed to read DC, and visa-versa.

--

JANA
_____


<colin2000@talk21.com> wrote in message
news:1119958372.694809.249730@g43g2000cwa.googlegroups.com...
i have an ac volt meter (0-12v). i wish to use it to monitor pc psu
voltage across an led. I have tried it for 30s and it works, showing a
steady, 'non shacky' 4v reading. So, is using a ac volt meter for dc
volt reading recommmended ?.....

 

[CWatters]

<colin2000@talk21.com> wrote in message
news:1119958372.694809.249730@g43g2000cwa.googlegroups.com...

i have an ac volt meter (0-12v). i wish to use it to monitor pc psu
voltage across an led. I have tried it for 30s and it works, showing a
steady, 'non shacky' 4v reading. So, is using a ac volt meter for dc
volt reading recommmended ?.....

Nope. What does it say when you hook up a 9V battery?

 

[CWatters]

"emma" <mrandmrsrelativity@yahoo.com> wrote in message
news:1119955232.771610.169150@z14g2000cwz.googlegroups.com...

What do you mean the electrons behave the same. In the Alternating
Current. It goes forward and backward in time, while in the Inverter,
it goes forward only. Isn't it.

No a Mains Inveter (if thats what you mean) is a device that converts 12V DC
to 110V AC to provide power for tools etc when you don't have a wall socket
handy (eg in the middle of a field). In other words it's output is similar
to what you get from a wall socket.

The drift velocity of the electrons are slow. In AC, how can it
have enough time to go forward and backward.

Because they don't move very far. They mostly just sit there and vibrate.
It's like the air in a room - it doesn't move much when you play the radio.
The sound waves and their energy go through the air but the air molecules
just vibrate.

 

[CWatters]

"emma" <mrandmrsrelativity@yahoo.com> wrote in message
news:1119955480.071262.157980@f14g2000cwb.googlegroups.com...

Whether you have 100 Ampere or 0.5 Ampere, The drift
velocity of the electrons in a given wire is the same right?

So how does the electrons behave in high amperage vs.
low amperage.

http://www.phys.unsw.edu.au/~jw/drift.html#electrical

 

[Bill]

"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:z_cwe.132241$Gi3.7020592@phobos.telenet-ops.be...

"emma" <mrandmrsrelativity@yahoo.com> wrote in message
news:1119955232.771610.169150@z14g2000cwz.googlegroups.com...
What do you mean the electrons behave the same. In the Alternating
Current. It goes forward and backward in time, while in the Inverter,
it goes forward only. Isn't it.

No a Mains Inveter (if thats what you mean) is a device that converts 12V DC
to 110V AC to provide power for tools etc when you don't have a wall socket
handy (eg in the middle of a field). In other words it's output is similar
to what you get from a wall socket.

The drift velocity of the electrons are slow. In AC, how can it
have enough time to go forward and backward.

Because they don't move very far. They mostly just sit there and vibrate.
It's like the air in a room - it doesn't move much when you play the radio.
The sound waves and their energy go through the air but the air molecules
just vibrate.

My understanding is that a typical DC to AC power inverter produces something
more like a square wave than a sine wave. In fact, I have an inverter and the
picture they show of the output is just like that except there are little gaps
"between the squares." You can buy more expensive ones that produce a shaped
output that looks more like a sine wave. But in addition to costing more, you
lose more power in the conversion.

Most devices - e.g. computers and light bulbs - respond perfectly well to the
inverter. But some motors generate more heat because of the shape of the wave
and you have to be careful.

Bill

 

[Charles Jean]

On 28 Jun 2005 17:13:06 -0700, "emma" <mrandmrsrelativity@yahoo.com>
wrote:

Hi,

I'm doing an experiment on the effect of load. Does anyone
know what component to put or use so I can convert the
Sine wave from the AC outlet to square wave with no changes
in frequency? Something that can smear the rising amplitidue to
a fixed value and the same in the opposite end. Can some
capacitor combination with other components do the trick?
Thanks.

emma
___

Whats the P-P voltage of the AC and its frequency?

Please describe one cycle of the square wave you want:
0 volts, step sharply to ?V
hold for ?wavelengths of incoming AC
step sharply to ?V
hold for ?wavelengths of incoming AC
step sharply to 0V

 

[Ken Taylor]

"emma" <mrandmrsrelativity@yahoo.com> wrote in message
news:1120003985.988751.284950@o13g2000cwo.googlegroups.com...

Hi,

I'm doing an experiment on the effect of load. Does anyone
know what component to put or use so I can convert the
Sine wave from the AC outlet to square wave with no changes
in frequency? Something that can smear the rising amplitidue to
a fixed value and the same in the opposite end. Can some
capacitor combination with other components do the trick?
Thanks.

emma

A sine wave is actually a 'smeared' square wave, not the other way around.
Be that as it may, depending on just how 'square' you want it, a cheap
non-sine UPS may fit the bill.

Ken

 

[St. John Smythe]

emma wrote:

I learnt that square waves for examples produced by power
interver has high frequency components.

Yes. That's what makes them square waves. Remove the high frequency
components, and you have sine waves.

What's the typical
value of the frequency supposed the source is 110 volts,
60 hertz.

Theoretically, multiple frequencies, extending to infinity.

Is there no way to remove the high frequency
components?

Yes, but not if you want to continue to have a square wave.

--
St. John

 

[Uncle Al]

emma wrote:

Hi,

I learnt that square waves for examples produced by power
interver has high frequency components. What's the typical
value of the frequency supposed the source is 110 volts,
60 hertz. Is there no way to remove the high frequency
components? How does it affect the load?

Bandpass filter.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf

 

In article <1120009031.592710.272250@g43g2000cwa.googlegroups.com>, "emma" <mrandmrsrelativity@yahoo.com> writes:

Hi,

I learnt that square waves for examples produced by power
interver has high frequency components.

Of course. They have to.

What's the typical
value of the frequency supposed the source is 110 volts,
60 hertz.

There is no such thing as "typical value", it depends how close to
suare you want them to be.

Is there no way to remove the high frequency
components?

Of course. You can filter away all but the fundamental. In which
case you're back to a sine wave.

How does it affect the load?

That depends on the load.

Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"

 

[Solarman]

emma wrote:

Hi,

I learnt that square waves for examples produced by power
interver has high frequency components.

That's why radios don't work well on with square wave A.C.

What's the typical value of the frequency supposed the
source is 110 volts, 60 hertz.

Is there no way to remove the high frequency
components? How does it affect the load?

The more expensive invertors let you switch from
square wave to sine wave when you want to run
something like a radio.

Power efficiency comes at a cost.

http://www.solarexpert.com/PVinvtinfo.html

 

[Tm]

"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:42C1FE4B.50666504@hate.spam.net...

emma wrote:

Hi,

I learnt that square waves for examples produced by power
interver has high frequency components. What's the typical
value of the frequency supposed the source is 110 volts,
60 hertz. Is there no way to remove the high frequency
components? How does it affect the load?

Bandpass filter.

Low Pass will do it. But you will need more than a 110 volt square wave to

start with if you expect to get a 110 volt sine.

TM