GCSE Physics - Alternating (AC) and Direct Current (DC) #21

This video covers:
- The difference between alternating current and direct current
- Voltage-time graphs
- Oscilloscopes
General info:
- Suitable for all GCSE and IGCSE courses
- Suitable for higher and foundation tiers
- Suitable for triple and combined science
Exam board specific info:
AQA - Everything is relevant to your course!
IGCSE Edexcel - Everything is relevant to your course!
Edexcel - Everything is relevant to your course!
OCR 21st Century - Everything is relevant to your course!
OCR Gateway - Everything is relevant to your course!

[@Cognitoedu]

Hi everyone - we just wanted to clear up a bit of potential confusion about whether UK voltage is 230V or 240V. *Be aware that at the time of writing you can give either figure in your exam and you'll get the mark.* Many resources will cite the UK voltage as 230V, however this isn't technically true. Historically, UK homes have been supplied with 240V, and EU homes have been supplied with 220V. In 2003, they 'harmonised' the voltages across the UK and EU, and so both were now labelled as 230V. However the actual voltage didn't change, but instead the official voltage requirements for any electrical goods made in the UK/EU were altered - so that they would work using voltages ranging from ~215V to ~250V - and work in both the EU and UK with no problems. It's nothing to worry about either way, but we hope this clears up any misunderstandings :)

[@stustjohn]

Thank you for clarifying this. However, you still have dropped one major clanger in this presentation! When you labelled the values on the voltage-time graph you said/wrote from +240 V to minus 240 V. This is not right. (Nor is it plus to minus 230 V.) The peak voltage will be √2 x 240 (or whatever value your supply actually is). Look up RMS voltage to find out why. (A level topic 🤓) I usually avoid putting values on the y-axis for most classes, as it raises an issue that cannot be satisfactorily answered for the average person! (If a class insists on knowing then I warn them, and if they still want to know then I give a 2 minute summary of RMS values... 😁)

[@caslonantique]

Indeed. However, your video claims (at about 1'20") that the UK mains fluctuates between ±240V and this is definitely not the case; the 240V figure is the root mean squared (rms) value, and so the peak voltage is actually about ±325V.

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[@Cognitoedu]

🙌

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Same

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This guy teaches me better in two minutes than my physics teacher does in an hour

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True

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Frfr

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omg you are the freaking best teacher I have ever had. Your explanations are so clear and easy to understand, same topic i spent hours on i understood in minutes. Am legit about to go into tears.

[@Cognitoedu]

Haha really glad we could help Zach 🙌

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Cramming the whole playlist night before the exam ganggg‼️😭

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stop calling me out my exam in 8hours💀

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very helpful resources.....not only for GCSE but also IGSCE i would highly recommend candidates doing the cie examinations use this content....... thank you for giving us this free and reliable resources

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[@talhaafzal180]

Amazing! I've gone through all the much worthy praise in the comments section but my only question is how can you be so flawless and to the point in 2 minutes? Kudos, indeed!

[@Cognitoedu]

🤩 Thank you very much Talha!

[@vt.physics]

Very useful video! My students always forget the difference between the two types of current!

[@siyasingh6076]

I loveeee your channel too Your videos are awesome!! Keep it up, lots of love.

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thunderstruck

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I am watching this an hour before my exams

[@universeusa]

Awesome. Thanks!

[@Cognitoedu]

Cheers Jake! Glad it’s helping 🤙

[@universeusa]

Cognito , yes, it is. Thanks 🙏 again.

[@yvonneg1006]

Its 230V in the UK not 240

[@Cognitoedu]

Hi Yvonne, thanks for your comment - I've made a pinned comment addressing this. Good luck with all your work!

[@kevinhanksable]

Thank you very much. Brilliant.

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How does AC look like in circuit? Does it go around the circuit and come back?

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what about the gold lesf electroscope ?

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GOD, can you drag it out anymore? So house is AC car is DC. …Man oh man!

[@princekaki5424]

it was very helpful i understand the topic better now

[@Cognitoedu]

Thanks Prince, that's great to hear 👍

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I don’t this is bullshit

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extremely useful

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Am i right?

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Why is AC better than DC for mains supply?

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acdc reference

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Not me sitting my physics GCSE paper 2 in an hour and a half 💀💀

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How was it 💀

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thanks cog

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Thanks!

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awesome

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Easington

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rock on

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just like AC/DC

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Me walking into my exam knowing that ac/dc is a band (and nothing else):

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