Used to watch these videos when I was a high school dropout and had a dream to study physics. Since I watched all of your videos, I have gotten my GED, done 2 years at a community college, and now am a Physics Major at University of Maryland working in a high powered laser optics lab. These videos started it all. I would watch them while at work and take notes on little sticky notes, which are still on the wall in my room. Thank you DrPhysicsA, seriously. You changed the entire trajectory of my life.
I had small particles and figments of knowledge from my teachers, but after watching this and taking notes, they've all combined to make a large mass of consolidated information. Thank you, my good Sir.
Thanks for kind comments. My videos are an amalgamation of AQA, OCR, Edexcel and Cambridge A level syllabus for both AS and A level (with the exception that I don't tend to do the biophysics parts). The videos in the A level revision playlist "Atomic Structure - A Level Physics" contains atomic energy levels and photon emission when electrons fall down to lower energy levels.
Hello. Can I say that I have really enjoyed watching this video and other videos of yours. I have been able to gain lots of information, in terms of my studies at both GCSE and A Level Physics, which the A Level Physics I'm doing distance learning. I'm also doing A Level Maths and A Level Further Maths, distance learning also. If it wasn't for people like you, who give up their free time to produce videos on such a good scale, I would be in a worse place. Can I say thank you very much for your help and support, it's appreciated very much. Regards Dominic G
You're a life saver. Your videos saved me like 50-60 pages of reading. Your explanations are thorough yet simple to follow and idk you just made my life THAT much easier.
Thank you so much. I have always had a problem with grasping the abstract essences of electricity. Your profound video has helped healed my wound and made me get it. Thanking you a thousand times would still not repay what you have done to the world.
Yes indeed. I can't now remember why I plotted it that way round. I suspect I was simply trying to show that there is a direct proportionality between current and voltage. But as you say, the slope of the graph which I drew is 1/R not R itself.
Thanks so much, with only a couple of weeks till my exam I wasn't sure if I could pass them, after watching your videos everything seems much clearer :)
V and r (internal) are constant. R (load) is variable. I = V/(R+r). Power thro Load = I^2 R = V^2 R/ (R+r)^2 = V^2/ R + r^2/R + 2r. Now for the power to be a maximum, the denominator must be a minimum. Diff w.r.t R and set equal to zero. You get 0 = 1 - r^2/R^2. So r^2 = R^2. So r=R.
Yes indeed. You will find a set of vids on QM in my Quantum Mechanics playlist (see main page of my RU-vid channel) and you will find additional Waves vids in the playlist on A Level Physics.
Well there is a quantum mechanical underpinning to all this, but for purposes of A level all I meant was that as the current passes thro the filament of the lamp it heats the filament (and thus produces the light). As the filament heats up, its resistance increases so the current falls. R increases because the electrons in the wire get more excited and therefore there are more collisions and interactions between electrons which impedes current flow.
It is "Atomic Physics 3: Semiconductors, Diodes and Transistors". But you might want to watch videos 1 and 2 first to set it all in context. You can find these on my home RU-vid page (drphysicsa) in the playlist Atomic Physics. Thanks for kind comments.
To help better my understanding of how electricity works, I envisioned myself being an electron whizzing around an electron which constantly reversed EPE as I deliver energy to different electrical components and release energy as light quanta.
Took physics in university a decade ago. Our professor stinks at really teaching us anything. Didn't understand a damn thing and its a miracle I managed to pass the courses. Anyway, I'm currently settled in my career unrelated to physics...but out of sheer intellectual curiosity decided to re-learn physics. I find your youtube channel highly valuable --"subbed." I am sure my life/career choices may have ended up differently had I actually understood this stuff a decade ago.
At 3:56, the point I'm trying to convey is that N if the total number of electrons flowing per second, Q is the total charge flowing per second and that that must therefore represent the current I.
Unless I've missed a point, the answer is that you need about 0.7v across the LED before any current will flow in the circuit. So for the first 0 - 0.7v I would expect no current. Thereafter, assuming there is a resistance in the circuit I would expect current to grow proportionately with voltage.
I think it was Benjamin Franklin who started the idea of electricity flowing from + to -. You will recall that electricity was used long before it could be explained quantum mechanically and before electrons had been discovered. It was therefore just unfortunate that current flow was determined to be the opposite direction to the particles which actually flow - ie the electrons.
EMF is voltage. So it is electric potential (V) - potential energy per unit charge. Electric Potential Energy (Ep) is work done moving a charge (q2) from infinity to a point r away from q1. The Electric Field (E) is the Force per unit charge.
N is number of charge carriers passing a given point per second. Q is the total charge passing a given point per second. But charge flowing per second is current. I=Q/t
YOU'RE AMAZING, better than my school teacher. I love your cyber lessons lol, keep doing what you're doing! Also i was wondering what syllabus you work according to? Im doing AQA A physics AS at the moment. Do you have anything on Energy levels and photon emission?
