Problems about circuit diagram full wave rectification

[PainterGuy]

hello everyone,

i am having difficulty in understanding this circuit diagram from a book:
http://img834.imageshack.us/img834/9462/ripplerectification.jpg

my questions are also present there in diagram. i will be very grateful if someone of you nice people can help me without complicating things for me.

 

[Jiggy-Ninja]

Those questions really have nothing to do with the rectifier itself.

The 120V 60Hz thing on the left represents a wall plug, that's it.

The dots on the transformer symbol show that the windings are wound in the same direction, so the primary voltage is in phase with the secondary. If the secondary dot was below the symbol, it would mean the windings are wound in different directions, and the primary and secondary are 180 degrees out of phase.

The curved capacitor means that it is an electrolytic capacitor. While capacitors are in principle not polarized (they work the same backwards as they do forwards), electrolytic capacitors are constructed in a special way that makes them only able to handle voltage in one direction. If you put it in the wrong way, it will destroy the capacitor (and potentially explode). The curved line on the diagram represents the negative terminal of the electrolytic capacitor, so that you know which way it needs to be hooked into the circuit.

 

[Proton Soup]

for the specific circuit in that figure, the marked ends on the transformer windings will not matter. the other thing you may or may not have noticed is that the transformer secondary is "center-tapped". that means your secondary will have 3 actual wires coming out of it. in this case, the center tap is referenced to 0V, so that the other two are equal in voltage, but 180 degrees out of phase. this allows you to get away with only 2 rectifier diodes instead of a full rectifier bridge with 4 diodes. but at half the full voltage across the entire secondary winding.

 

[PainterGuy]

Jiggy-Ninja many thanks for helping me with this. actually i was writing some questions for you in some other thread.

The 120V 60Hz thing on the left represents a wall plug, that's it.

yes, it is a wall plug. yes i am stupid but not that much! but this plug 'originally' had three terminals. in my opinion (which obviously could be false) it should have two terminals. is my modification correct? do you see where i am having problems?

The dots on the transformer symbol show that the windings are wound in the same direction, so the primary voltage is in phase with the secondary. If the secondary dot was below the symbol, it would mean the windings are wound in different directions, and the primary and secondary are 180 degrees out of phase.

i think to understand this windings being in same direction and opposite, i need some diagram etc. can you please tell me phrase or search words to use on google. i searches using some words but it didn't produce results. to me winding in either clockwise or anticlockwise direction does not make a difference!

many thanks for helping with many problems. much grateful for this teaching.

cheers

 

[Proton Soup]

try this: http://www.google.com/search?q=cent...s=org.mozilla:en-US:official&client=firefox-a

 

[Jiggy-Ninja]

yes, it is a wall plug. yes i am stupid but not that much! but this plug 'originally' had three terminals. in my opinion (which obviously could be false) it should have two terminals. is my modification correct? do you see where i am having problems?

No, your modification is incorrect. The way you drew it, the transformer with get the same voltage on both ends of it, and it won't do anything. It'd be like hooking a lightbulb up to just the positive end of the battery and expecting it to light.

The three terminals are for "hot, "neutral" (which is where your current is flowing through), and "ground", which is an Earth ground rather than a circuit ground.

i think to understand this windings being in same direction and opposite, i need some diagram etc. can you please tell me phrase or search words to use on google. i searches using some words but it didn't produce results. to me winding in either clockwise or anticlockwise direction does not make a difference!

many thanks for helping with many problems. much grateful for this teaching.

cheers

There was a diagram in my textbook, I'll see if I can find a comparable illustration...

If both winding are in the same direction (both clockwise or both counter-clockwise) then the voltages will be in phase. It's if they are wound in opposite directions (one clockwise and the other CCW) that the voltages are 180 degrees out of phase.

 

[PainterGuy]

hello Jiggy-Ninja,

you are very nice and kind. i wish you were my teacher in school.

Proton Soup i did not miss your post. it helped me. much thanks.

No, your modification is incorrect. The way you drew it, the transformer with get the same voltage on both ends of it, and it won't do anything. It'd be like hooking a lightbulb up to just the positive end of the battery and expecting it to light.

The three terminals are for "hot, "neutral" (which is where your current is flowing through), and "ground", which is an Earth ground rather than a circuit ground.

iggy-Ninja, you or anyone who is going to help me should first know what i think of AC, check this post:
https://www.physicsforums.com/showpost.php?p=3205480&postcount=1

where i live we always use plugs with two terminals. my tv, fridge, dvd, computer, everything. there is no third plug. when i insert http://image.shutterstock.com/display_pic_with_logo/63701/63701,1163508007,4/stock-photo-screwdriver-electric-tester-2167940.jpg" in any of the slots of female plug the tester lights up - which means both slots have current. at any time if in one wire electrons are being pushed then in other wire being 'pulled'. in order for the current to flow there should be a connection between these two wires!

i think what you are talking about neutral, hot wires, i am already discussing in the same thread and i am much confused already: https://www.physicsforums.com/showpost.php?p=3209963&postcount=4

There was a diagram in my textbook, I'll see if I can find a comparable illustration...

If both winding are in the same direction (both clockwise or both counter-clockwise) then the voltages will be in phase. It's if they are wound in opposite directions (one clockwise and the other CCW) that the voltages are 180 degrees out of phase.

i hope you find that diagram soon. i still think it does not matter if it is clockwise or anti clockwise (yes, yes, i know i am wrong!:shy:).

many thanks for teaching me all this.

cheers

 

[Jiggy-Ninja]

hello Jiggy-Ninja,

you are very nice and kind. i wish you were my teacher in school.

I'm pretty much the unofficial teacher's aide in my classes. It's a compulsion of mine.

Jiggy-Ninja, you or anyone who is going to help me should first know what i think of AC, check this post:
https://www.physicsforums.com/showpost.php?p=3205480&postcount=1

where i live we always use plugs with two terminals. my tv, fridge, dvd, computer, everything. there is no third plug. when i insert http://image.shutterstock.com/display_pic_with_logo/63701/63701,1163508007,4/stock-photo-screwdriver-electric-tester-2167940.jpg" in any of the slots of female plug the tester lights up - which means both slots have current. at any time if in one wire electrons are being pushed then in other wire being 'pulled'. in order for the current to flow there should be a connection between these two wires!

i think what you are talking about neutral, hot wires, i am already discussing in the same thread and i am much confused already: https://www.physicsforums.com/showpost.php?p=3209963&postcount=4

None of them are 3 prong? Where do you live? It seems very unsafe to use metal appliances without a ground, so they must be doing something that I don't know about. I'm only familiar with the US electric system (since that's where I live), and quite a lot of things have 3 prong plugs (but not everything).

With 120V 60Hz example diagram, your textbook looks to be American-made.

That device is not a current tester, it is a voltage probe. If there's nothing plugged in, there should not be any current. And a couple of articles I just read about how it works imply that if it reads voltage of a line, it's not grounded. So if your hot and neutral aren't grounded...without knowing the electric code of your country (I don't even fully know my own yet) I'm going to stop speculating further about that. Now I'm curious how stuff is grounded in your country.

i hope you find that diagram soon. i still think it does not matter if it is clockwise or anti clockwise (yes, yes, i know i am wrong!:shy:).

From the beginning:

The basic theory of electromagnetic induction is that when a conductor is moved inside of a magnetic field (or a magnetic field moved across the conductor) voltage is generated in the conductor. The polarity of that voltage depends on the direction of movement. Move it one way, it will give you a positive voltage. Move it the other way, it will give you negative.

Moving electric charges also create a magnetic field. When the current increases, the magnetic field around the wire increases (expands). When the current decreases, the field decreases and contracts.

With AC current, since the current is constantly changing, the magnetic field is also changing, expanding and contracting several dozen times a second, and inducing voltage in the wires. That is called "self-inductance". The coil construction and ferrous cores of inductors are made to increase that effect.

Transformers use "mutual inductance", where the expanding and contracting magnetic of one coil (the primary) induces a voltage in a different coil (the secondary). When the coils are wound the same way, the magnetic field lines pass through the wires the same direction (relatively speaking) so the same voltage is induced in both of them. When the coils are wound opposite ways, the magnetic field lines cut through the secondary in the opposite direction (again, relatively speaking), and induce an opposite voltage.

 

[PainterGuy]

hello Jiggy-Ninja,

you are very nice and kind. i wish you were my teacher in school.

Proton Soup i did not miss your post. it helped me. much thanks.

Jiggy-Ninja, you or anyone who is going to help me should first know what i think of AC, check this post:
https://www.physicsforums.com/showpost.php?p=3205480&postcount=1

where i live we always use plugs with two prongs. my tv, fridge, dvd, computer, everything. there is no third prong. when i insert http://image.shutterstock.com/display_pic_with_logo/63701/63701,1163508007,4/stock-photo-screwdriver-electric-tester-2167940.jpg" in any of the receptacles of female connector the tester lights up - which means both receptacles carry current. at any time if in one wire electrons are being pushed then in other wire they are being 'pulled'. in order for the current to flow there should be a connection between these two wires!

i think what you are talking about neutral, hot wires, i am already discussing in the same thread and i am much confused already: https://www.physicsforums.com/showpost.php?p=3209963&postcount=4

i hope you find that diagram soon. i still think it does not matter if it is clockwise or anti clockwise (yes, yes, i know i am wrong!:shy:).

many thanks for teaching me all this.

cheers

hi,

I'm pretty much the unofficial teacher's aide in my classes. It's a compulsion of mine.

it is very good compulsion to help others. i salute this compulsion!

None of them are 3 prong? Where do you live? It seems very unsafe to use metal appliances without a ground, so they must be doing something that I don't know about. I'm only familiar with the US electric system (since that's where I live), and quite a lot of things have 3 prong plugs (but not everything).

i would ask someone what do they do to ground stuff or prevent electric shock? but first i should know and understand how do you use that third prong for ground. can you please have a see on this thread:
https://www.physicsforums.com/showthread.php?t=483727

in this thread from post#4 onward i start discussing this neutral, live and earth/ground wire problem and how ground works.

this http://citizenselectric.apogee.net/foe/fsg3p.asp" shows the three prong plug.

So if your hot and neutral aren't grounded...without knowing the electric code of your country (I don't even fully know my own yet) I'm going to stop speculating further about that.

i have never heard this electric code of country thing before. where can i find this list? i googled to no success.

From the beginning:

The basic theory of electromagnetic induction is that when a conductor is moved inside of a magnetic field (or a magnetic field moved across the conductor) voltage is generated in the conductor. The polarity of that voltage depends on the direction of movement. Move it one way, it will give you a positive voltage. Move it the other way, it will give you negative.

Moving electric charges also create a magnetic field. When the current increases, the magnetic field around the wire increases (expands). When the current decreases, the field decreases and contracts.

With AC current, since the current is constantly changing, the magnetic field is also changing, expanding and contracting several dozen times a second, and inducing voltage in the wires. That is called "self-inductance". The coil construction and ferrous cores of inductors are made to increase that effect.

Transformers use "mutual inductance", where the expanding and contracting magnetic of one coil (the primary) induces a voltage in a different coil (the secondary). When the coils are wound the same way, the magnetic field lines pass through the wires the same direction (relatively speaking) so the same voltage is induced in both of them. When the coils are wound opposite ways, the magnetic field lines cut through the secondary in the opposite direction (again, relatively speaking), and induce an opposite voltage.

(i know what i say is wrong but you must know why i think opposite of what you told me). suppose you are winding a wire around a pencil, then i don't think winding it clockwise or anticlockwise make any difference. if looking from above makes it look you are winding in clockwise direction, then looking it from below makes it look you are winding anticlockwise. in my "wrong" opinion this clockwise and anticlockwise doesn't matter.

cheers

 

[Jiggy-Ninja]

i would ask someone what do they do to ground stuff or prevent electric shock? but first i should know and understand how do you use that third prong for ground. can you please have a see on this thread:
https://www.physicsforums.com/showthread.php?t=483727

in this thread from post#4 onward i start discussing this neutral, live and earth/ground wire problem and how ground works.

this http://citizenselectric.apogee.net/foe/fsg3p.asp" shows the three prong plug.

Your post at #9 in that thread sums up what I know about Earth connections too. Can'treally add anything to that.

That picture looks to be a US 3-prong outlet. I'm quite familiar with what they look like already.

i have never heard this electric code of country thing before. where can i find this list? i googled to no success.

The electric code is just a bunch of rules and regulations that your government has so that every building is wired up roughly the same way, making them safe and easy to service for other electricians.

(i know what i say is wrong but you must know why i think opposite of what you told me). suppose you are winding a wire around a pencil, then i don't think winding it clockwise or anticlockwise make any difference. if looking from above makes it look you are winding in clockwise direction, then looking it from below makes it look you are winding anticlockwise. in my "wrong" opinion this clockwise and anticlockwise doesn't matter.

cheers

Your example is wrong.

If you wrap a single coil around a pencil, you are making an inductor, not a transformer. As you noted from your model, the absolute winding direction does not matter for an inductor; it is the same either way.

A transformer, however, is made from two coils, and it is the difference in their winding directions that matters.

To modify your pencil model, take two lengths of wire. Wind one around the top half of the pencil, and the other around the bottom half, so that you have two separate coils. If you look from the top, you see that they are both wound clockwise. Turn the pencil over, look from the bottom, and you see that they are both wound counter-clockwise. They are both wound the same direction, no matter which way you look, so the voltages of the two coils will be in phase with each other when you use the "transformer".

Now let's undo the coils, and rewind them. Looking from the top, we wind the first coil clockwise, and the second one counter-clockwise. Now, if you look from the bottom, it looks like the first coil is wound counter-clockwise, and the second coil wound clockwise. No matter how you look, they are wound in opposite directions, so their voltages will be opposite (180 degrees out of phase).

CW and CCW don't matter, what matters is whether the two coils are wound in the same or different directions.