Capacitors, DC and AC Current

[san42c02y]

Thanks,i learnt something very important from this clip.

[AllAmericanFiveRadio]

Thanks san42c02y

[512147214]

greaaaaattttttttttttttt explaination i hv becom ur fan i swear i accept u my teacher ;-) v nice

[512147214]

and y we need to use?????????????????

[512147214]

hi brother ur presentation is very nice my concept has ben cleard......but brother tell me one thing......

why we use capacitor and inductor in an A.C and D.C circuits......>>>>>>>>>>>>>>>

plz give me concept abt these questions i ll b v thankfull 2 u??????????????????

[AllAmericanFiveRadio]

@512147214

There's not one answer. You can use a capacitor to isolate an AC signal riding on top of a DC bias voltage, this is very common. You can use capacitors to filter a DC power supplies. You can use capacitors to drain unwanted RF from a circuit. Inductors can be use for the same things but are configured in the circuit differently. Sometimes a capacitor works better, sometimes an inductor works better. It takes some study to understand why.

[TurKdiRty]

it would be nice to see the effect different frequencies have

[mamu7mich]

can you please explain why does for ac in a capacitor the current leads the voltage?? i know about the graph but why is this so?

[AllAmericanFiveRadio]

@mamu7mich

In this simple circuit there is no lead with the current through the capacitor and the voltage across it on the first half cycle. When the voltage is first applied there is a large current flow and it diminishes as the capacitor charges. Now the cap is charged, and this energy in the cap can ad or deter current flow depending on the AC frequency and the capacitance of the cap. It take time to charge and to discharge a capacitor.

[AllAmericanFiveRadio]

@toyu17

Any capacitor can be charged with a DC current, that is what the diode is for. If you use to much current the capacitor can explode. To charge a high capacity capacitor we used a 60 watt light bulb in series with the diode. It will glow bright at first then get dimmer as the capacitor charges. Be careful with polarity, if you charge it in the wrong direction, the capacitor can explode.

[AllAmericanFiveRadio]

@toyu17

Charging a capacitor with DC, charges in one direction. Charging a capacitor with AC, charges in one direction and then in the other direction with the AC that is used. When you stop the AC charging the capacitor, the capacitor will be charged with DC at the point where the AC stopped.

[fairyheli2]

now i understand induction motors! thanks

[AllAmericanFiveRadio]

Thanks fairyheli2

[Mess1410]

Great Job ! thank you !

[AllAmericanFiveRadio]

Thanks Mess1410

[anyone9991]

Thank you :) You're a good teacher

[AllAmericanFiveRadio]

Thanks anyone9991

[brandonz404]

Thank you sooooo much! this really helped me understand a AC a LOT better. haha I knew nothing about it.

[AllAmericanFiveRadio]

Thanks brandonz404

Hope this helps!

[roti822000]

Many thanks,u r a good teacher

[AllAmericanFiveRadio]

Thanks roti822000

[powermaks]

in AC is the cycling of CURRENT, VOLTAGE, or BOTH?

[AllAmericanFiveRadio]

@powermaks

Usually both.

[exee11]

i dont get one thing....

whats the difference in AC AND DC,,, i mean... y the polarity is chnaged in AC ... and why DC doesnt show the lower half cyclee...??? plz/hhhelp

[AllAmericanFiveRadio]

Thanks exee11

Think of DC as a battery that never runs down. If it is a 12VDC battery, it stays at 12VDC and does not change with time. So that is why DC only has one potential and one direction. Hope this helps.

[exee11]

@AllAmericanFiveRadio

erm..

thnkyou for that..but a lil confusion ..

-why doesn't capacitor allow DC to flow through it?

-for 'charging the mobile battery,reachargable cells . .etc . . . ' doest it has some connection with the type of current (AC OR DC) ??

--waiting for the answers.. :S

thnkyou!

[salimkhan007]

@AllAmericanFiveRadio one thing i want to know about.when the capictor is fully charg and we take it out from the circuit and provied discharging path to the terminal of the capcitor.what will be the discharging current (DC or AC current )plz reply if any one know the answer.

[hardstyle905]

@salimkhan007 Max discharge current is I = U/R

[AllAmericanFiveRadio]

@exee11

If it is DC or AC there is no electronics that flow between the plates. The current flow is only due to the charging and discharging of the capacitors plates.

[78recordrepair]

With the battery aren't you showing constant voltage? Likewise, in the case of AC isn't it the voltage that's alternating?

[AllAmericanFiveRadio]

@78recordrepair

The voltage is almost constant from the batteries, but the current stops when the cap is charged. With AC both the current and voltage alternate. If you have lots of voltage and little current you don't have much power, add current and you do.

[Vinylrecordsneverdie]

Great demo!

[AllAmericanFiveRadio]

Thanks Vinylrecordsneverdie

[Albinorama]

do more videos like this!!!Thanks!.

[AllAmericanFiveRadio]

Thanks Albinorama

I'll be glad to and if you have some ideas let me know, I'll do them if I can.

[gurtobe]

as always-great video

[AllAmericanFiveRadio]

Thanks gurtobe

[xXDominoXx]

thank you :D

[AllAmericanFiveRadio]

Thanks xXDominoXx

[CameramanLink]

So the capacitor in an AA5 radio that passes leftover RF to ground before the audio amplifier doesn't actually "short" the RF, it just changes the charges so that it is canceled out? Maybe I'm not getting something here: a coupling capacitor in an audio amplifier only has AC (audio) on one side, but the other side is at constant potential because it is connected to the next tube's grid and grid resistor to ground. Why does it work in this case?

[AllAmericanFiveRadio]

CameramanLink

At the detector plate of an AA5 you will have RF and Audio. You do not want to amply the RF so the RF is drained off through a pf cap to ground. The RF energy is transfered though this capacitor to ground. The audio continues though another capacitor to the grid of the next audio amplifier. The audio cap and the pf cap both block DC.

[AllAmericanFiveRadio]

CameramanLink

At the plate of the detector it may have 90VDC, if the audio cap did not block DC you would have 90VDC on the grid of the next audio amp tube instead of just a volt or so. neat stuff isn't it

[joernone]

Rick,

Excellent video demo. Very well done. I liked the graphics. I know that took some time and effort to put together.

Regards,

John

[AllAmericanFiveRadio]

Thanks joernone

John,

I got a good idea from a YouTuber to make another video showing the results of this video by using a light bulb. I think that is a great idea.

Regards

Rick

[xXDominoXx]

@AllAmericanFiveRadio if you made a physical demonstration of this video, that would be excellent, thank you.

[trailkeeper]

Good vid. I think the larger the capacity (F) of the capacitor, the longer it will allow to take charge or current; (ie. the longer to charge up to the peak voltage of the input signal). 

[AllAmericanFiveRadio]

@trailkeeper

The size of the capacitor and the frequency of the AC is very important. This is very useful in circuits to control or filter.

[dnl5649]

great vid Rick! if you put ac on a capacitor, wouldnt it smooth out the current and also make some heat. i dont think ive ever messed with ac and capacitors before. well i have in radio power supplies

[AllAmericanFiveRadio]

Thanks dnl5649

Used as a filter, yes. This use is for transferring audio or RF signals and blocking the DC potential.

[dnl5649]

@AllAmericanFiveRadio in the power supplies, does it keep the 60 hertz from the power out of the rf circuit or keeps the rf out of the current and making it self oscillate. im pretty sure it leaks the 60 hertz into the rf circuit

[bearing01]

@dnl5649 The capacitor will pass the alternating current through it without "smoothing" it out. The current flows through the capacitor before the voltage is seen across it. The capacitor acts as an integrator or accumulator for charge/current. When the current flows, the charge builds up on the plates and that build up creates voltage across the plates. There is no heating because the cap doesn't dissipate energy. It stores the electrical energy and gives it back when it is discharged.

[coondogtheman1234]

what about starting capacitors are they any different than these?

[AllAmericanFiveRadio]

coondogtheman1234

Like in a motor?

[coondogtheman1234]

@AllAmericanFiveRadio

Yes, AC Induction motor. those black things you see inside a fan with RU, 250VAC 3mF etc written on them are those any different than a regular capacitor? I took apart a window fan and it has 2 of them inside. they wont run without them I don't think. the motors said duracraft on them. I was wondering if you hooked the cord right to the motor if they would work any better. probably not.

[bearing01]

@coondogtheman1234 The caps in a motor are the same as in this video. The induction motor will likely run fine without them, after it starts spinning, but will draw more current for a given torque load. The cap does 2 things: 1) Delays the magnetic field in a 2nd winding to make the magnetic field appear to rotate - to start the rotor spinning and 2) performs power factor correction by canceling out a portion of motor inductance to reduce the current required to deliver power to the motor.

[AllAmericanFiveRadio]

@coondogtheman1234

besides a starter capacitor there is a winding also to start the motor and a centrifugal switch that opens at about 75% of full speed. That circuit shift the phase to start the motor rotating. Google "start capacitor" or "AC motor" there is lots of good information.

[coondogtheman1234]

@AllAmericanFiveRadio

not in this fan. its a 3 speed induction motor and the starting cap is just this black rectangular thing with 2 wires going into it. I was thinking of just wiring up the motors to the switch correctly and without the caps. but it's kinda too late as I tossed this fan but I saved the blades maybe I can use them elsewhere.

[patchcords]

This is a great training video for the new guy to electronics !

Very well explained :-)

[AllAmericanFiveRadio]

Thanks patchcords

[THEtechknight]

Also, can you do a video on how impedance matching circuits work in RF amplifiers? I understand their functionality, but actually what makes them tick....

[AllAmericanFiveRadio]

Thanks THEtechknight

lol, good idea I have put this in my ToDo list.

[dreamyear]

good video...

[AllAmericanFiveRadio]

Thanks dreamyear

[THEtechknight]

Now, i loved that presentation you did there.

Can you do one on inductors/coils? because they pass DC but block AC. (to an extent)

[AllAmericanFiveRadio]

Thanks THEtechknight

I have put this idea in my YouTube ToDo list.