As many people here comment, (also IMHO) you are the best tutor i've ever listened to. ... Your explanations are gold. Pure gold. Im enjoying it so much.
RIGHT? This guy is utterly amazing. If I manage to invent/design something I'll be including your name on the patent! Since I was a young boy, I've always felt that the future of transportation, among other things, will be dictated by some manipulation of the EMF. These videos have sharpened my understanding of many things, and for that sir, I thank you.
If you're looking for the next wave of technology then understanding magnetism, other than what is presented, is vital. There is great explanation in these videos and only helps compound the proofs of more to the equation than meets the eye. Viktor Schauberger and his work(books, patents;not nonsense videos people post about him today) will help anyone on this path.
I must say that you have hands down the best tutorials for A Level physics. What I love is that you don't leave out the important maths that is involved in learning these concepts (the a level physics syllabus has a suprisingly small amount of math involved)
Covers every single point in the syllabus in a simple, easy to understand way. I learnt more in 45 minutes than what we learnt in 2 weeks of lessons. Thanks!
Your videos have helped solidify my understanding of electricity principles. I am delighted. Thank you so much for taking the time out to publish these!
i graduated high school in 2005, trashed physics at A-level in Hong Kong. now im getting older and like to revise on these stuff. I wonder if i had a teacher like you back then, i wont be where im sitting now. Thanks and i must say, you are a great teacher!!! Ray from Australia
Dude seriously its good to hear that you still have interest in something that you were not good at. People get scared from maths or other subjects at which they are not good however when you study from scratch and make notes and collect other helping stuff you can easily cover any subject at least this is what i believe in. Good to hear that you haven't given up even though you might never have any relation to this topic in the coming years.❤
I am a high school physics teacher and I have listened to a lot of RU-vidrs derive Maxwells equations and you have done imho the best job that a high school student can understand
Yes. If you go to my A Level Revision playlist you will find that videos 29-38 fit the bill. There is also a separate playlist on quantum mechanics with several videos at a deeper level than A level.
All A level videos are AMAZING!! Badly needed these explanations! :) Thankyou SOO much for this. Can't thank enough :') Your explanations are great. Concepts are perfectly clear now! Stay blessed, sir
Just wanted to say thanks for your super clear videos! I can't get over how you make complicated topics seem extraordinarily simple. (I'm more so referring to your video on how you derived Maxwell's 4 equations, but still great nonetheless!) As an electrical engineering/physics major I am thoroughly enjoying these videos.
You sir are an excellent teacher! I have watched, read, and listened to many of these concepts many times over the years and while I understand a good bit fairly well by now, many points you went over I just now finally can understand thanks to you and your explanations. I still plan to watch this again and practice the math by hand, but you explanations make this complicated subject MUCH easier to ingest. Thank you VERY much for this and your time!!
Thank you very much for your effort. I am a civil engineer, I wish I had you as a teacher in college courses, I might understand AC today! Thanks again
Thats a great video! But you might have made a mistake. In the beginning of your tutorial, when you determined the direction of the current in the coil of an ac generator when it's turned in a clockwise direction, you used flemmings left hand rule. Instead, you should have used flemmings right hand rule. If you did so, the direction of the current would be opposite to the direction you specified. This is all because in ac generators, the induced e.m.f follows the Flemmings right hand rule.
Rudra Ghosh He used left hand rule to find the current direction from the direction of the external magnetic field and the direction of the force acting on the loop of wire. This is correct since the right hand rule works for the cross product of the current and the external magnetic field direction, essentially giving the inverse.
Super Tutor... helped me greatly, always struggled in college with electronics & the math side of things... if only they had the staff.. but its all coming back and makes perfect sense. thankyou
Good questions. More about technology than physics. The windmills have a very clever gearing device which is capable of self adjustment to ensure that the turbine itself produces electricity at the appropriate frequency. The entire national grid monitors demand on a moment by moment basis and can switch in or out additional generators as the case may be.
Yes, I could see that was your point. By the way, out of curiosity I looked at the web for other accounts and other graphs and was astonished to find this to be a common error. Of course the square root of the power would look like the absolute value of sin, which may be in the back of people's minds. Anyway, as I said, otherwise, I thoroughly enjoyed your lesson!
You will get hurt if you hold the neutral wire. Please don't try it. In the UK the colours are red/brown for live, blue/black for neutral and green/yellow for earth. If you touch either the live or neutral you could get a shock.
Thanks alot DrPhysicsA... Your videos are extremely helpful.. more so than attending a physics class... because you explain everything so well and clearly. :D
Re Q2: A filament bulb on an AC circuit is being turned on and off at a rate the same as the frequency of the alternating current, for example 50 times a second, because this cycle is so fast the filament does not have time to cool down and loose light output. An LED (Light emitting DIODE) only allows current to travel in one direction, the light is not produced by heating a filament so as soon as power is cut the light stops. On AC this will happen for every negative voltage cycle.
I would point out that the representation of the Sin squared waveform (explained from around 19:44) is incorrect. It does not look like a full rectified sine wave - in fact it is a sine wave of double the frequency, centered at 0.5Vo. That is where the average value of 0.5 comes from (since the average of the sine wave component is zero).
the root mean square is the average voltage and average current that the resistance load can sense , since it doesn't detect a change in the direction of flow , of current or voltage. unless adding a magnet to the load , it starts sensing the change and starts motion
I'm not sure if someone in the comments has said it or not, but PLEASE do not just stick a large cap in the circuit! You'll waste a lot of power that way. If you were using a Three Terminal Regulator, then the larger your Vmin is (the lowest trough that the capacitor discharges too), the more power is on the input of the regulator. A TTR only needs Vmin to be at least a certain voltage above your desired output voltage load, which in the case of the LM317 is 2V. Then to calculate power dissipated by the TTR, you take the power of the input from the full-wave rectifier and capacitive filter minus the expected output power. Only using the Vmin you need rather than an excessive Vmin can lower the abuse your device will take in terms of heat/necessary cooling!
Well spotted. At 3:57 it should indeed be the right hand rule (rlght hand for generators - left hand for motors). I have made an annotation. Thanks for spotting this. As far as your second question is concerned, unless there is something I have missed an LED will light only when it is forward biased (ie the current flows in the forward direction thro it). Otherwise no current flows and the LED doesn't light. Perhaps there is more to it in your text book. Is it something to do with decay time?
Yes that's true but the Capacitor holds a much more steady voltage so this is the steady voltage which applies even if another voltage source in the circuit falls.
Sir I have a small question, when you were discussing the topic of transformers, you said that the voltage in primary is given by Vp= Np*rate of change of flux, and voltage in secondary is given by Vs=Ns*rate of change of flux. Now my question is: in secondary, it makes sense that the voltage induced in it is given by that formula, but why is it so in the primary? since the primary voltage is not dependent on induction at all. Hope you understood my question.
There is a difference between a generator and a motor. In the former case you turn a coil in a magnetic field. There is a phase difference in this case between the maximum flux linkage and the maximum current. in the case of the motor current flows in the coil in the presence of magnetic field causing the coil to turn. In this case there is no phase delay between the maximum voltage and current.
Sagar - In this case the V^2 term applies to the voltage in the wire, not the load. It is better to think in terms of the formula P=I^2R (1) for power dissipated in the transmission cables. Since P=VI, if we double the voltage that we are sending down the cable, to get the same power at the end the current is halved. But, because of the I^2 term in (1), the power "wasted" in the cables goes down by a factor of 4. Or look at it another way - we need a 1/4 of the copper to transmit the same power. The downside is that we need more insulation, but that is cheaper, and lighter than copper. In many cases we can even rely on air to provide the insulation.
Excellent - Thank you very much. I think some explanation is needed on the two back diodes on the FWR(@41:18). I guess the two back diodes 'meet' at DC Ground?
You have some highly educational videos! i'm watching these to refresh my school from a few years back and just out of general interest in understanding electricity :) thanks
hi i love your videos. They have helped me out alot.. Could you please do the unit 4 past paper questions?? i really need help with those especially multiple choice
I'll put it on my "to do" list. Meanwhile have you seen the excellent videos of Leonard Susskind's lectures on String Theory which you can find on RU-vid?
I see how you derived the formula for the average Voltage in AC at 20:41 and it does make sense. However I wonder what does another way of deriving it really mean: 1. I integrate the equation of Voltage from 0 to T/2 (taking only positive area): Integral[V0 * sin(omega*t) dt] from 0 to T/2. The result is -V0 * cos(omega*t)/omega from 0 to T/2. Evaluating gives me: V0 * T / pi. 2. I take the area under the curve and divide by change in T -- the length of the bounds of integration: V0*T/pi*(T/2 - 0) = 2V0*T/pi*T = 2V0/pi. Therefore I could conclude that the average Voltage is 2V0/pi. However this value is obviously much different than V0/sqrt(2). What does this quantity represent? Does it have a name? Thanks for all your videos, they are great in helping me understanding a variety of topics in physics. You are amazing at explaining things with simple words, yet not abstaining from maths :)
Yes. It is the left-hand rule for motors and the right-hand rule for generators. I think I may have added an annotation to correct an error. But I know that not everyone can see the annotations.
DrPhysicsA Actually, it is either. As long as the rules are consistently applied. If you choose to use the right-hand rule for a generator then you must also use the right-hand rule for a coil and the right-hand rule for a conductor and the left-hand rule for a motor. You can switch which hand to use to apply the rules if you apply all of the associated rules to that hand also. It is quite similar to the difference between conventional theory current flow and electron theory current flow. Does current flow from + to -, or - to + ? No one truly knows. But if one consistently applies the theories and rules throughout their work then their work will make sense.
7:45 I have another idea by Maths at this point the current would have passed an angle of 270 And sin270=-1 so that's why the Vmax is in opposite direction :D
As usual u r just amazing.... but I 've a doubt on the current transmission.... Power dissipated in the wire can also be written as V^2/R . So if we supply the current at a higher voltage in the transmission cables, according to the above equation power dissipated will be large . Can u plz help me out in this stuff...
You explain it well, tried to teach it to my niece I but have no talent as a teacher either patience. I also think that the new manuals are mediocre, don't try to teach you how to think in a logical sequence.It's more like a catalog with a lot of pictures with descriptions.
The power dissipated in a filament is the one shown at min (18:00). If the AC frequency is high enough, even when the instantaneous current (power) is 0, the filament will still glow b/c its temperature changes much slower. Nevertheless the filament will flicker, but never really turn OFF like in the LED case. I think this what they mean. Checkout this youtube video:9HUrYoqxQpw
