GCE (A-level) Physics E31 Alternating Current (AC) Part 2 of 2

Explains how to calculate power in (resistive) AC circuits using peak and RMS (root mean square) values of voltage and current.

[benedictpagani]

There videos have been so helpful!
I feel so much more confident about my physics exam now!
Thank you so much!

[yongseng]

left 4 days then I've to sit for my final HUGE exam, your video extremely useful for my revision!thanks!

[suzumiya]

Thank you so much! youve been a great help. I wasnt all that good with AC at first, but you cleared a lot of doubts for me. thanks again

[Chitaune]

i have watched all of the GCE alevel physics (E) videos and they have been a great help and helped me understand the majority of the topic from my specification. Thank you very much :) i am surprised that you have only got hundreds of views. it deserves to get millions.
I was also wondering if you will be putting up a similar kind of series covering the particle physics aspect of unit 1 (AQA). me and a lot of people have got AQA unit 1 exams in January and it would be a great help. Thank you!

[StevePhysics]

RMS voltage (or current) is the steady voltage (or current) that gives the same power as the alternating voltage (or current).
For a square wave, Vrms is simply the amplitude. E.g. you have a square wave ‘flipping’ between +5V and –5V. Then Vrms = 5V.
For example, watch the preceding video (E30 Alternating Current (AC) Part 1 of 2) from about 10min onwards. It shows a square wave ‘flipping’ between +1.5 and –1.5A. This has the same power as a steady 1.5A. So Irms = 1.5A.

[StevePhysics]

Hi Chitaune. Thanks for the positive feedback. Unfortunately I won't be making any videos on Particles in the near future. Progress in making these videos is very slow I'm sad to say.
Good luck in your exam in January.

[StevePhysics]

@Chitaune

Hi Chitaune. Thanks for the positive feedback. Unfortunately I won't be making any videos on Particles in the near future. Progress in making these videos is very slow I'm sad to say.
Good luck in your exam in January.

[TommyMorrisUK]

Hey Steve! I have seen most of your videos on electricity for AS.They have been a great help, so thanks ... I don't suppose you could do videos on particle physics now (for AS ) because that would be an even greater help !

[StevePhysics]

Hi. It’s not a rectified shape.

Plot graphs of y=sin(x) and y=sin²(x) using a calculator and see the shapes for yourself.

For a fixed resistance, power is proportional to current squared.

I = I₀sin(ωt)
I vs. t graph has same general shape as y=sin(x) graph.

I² = (I₀sin(ωt))² = I₀²(sin²(ωt))
I² vs.t (and P vs. t) graph has same general shape as y=sin²(x) graph.

For a more mathematical explanation, note:
sin²(x) = ½[1 - cos(2x)]

This gives I²= ½I₀²[1- cos(2ωt)] which is a sine-like shape.

[suriedeepthi]

I wanted lectures on geometric and physical optics

[StevePhysics]

Sorry I've no plans to do these in the near future. However if you search in YouTube, there are some good videos on them.

[OviedoSaul]

Hey.. how can I get the Vrms of a squere wave?? help me! please!