GCE (A level) Physics E03 Emf and voltage. Part 1 of 2

[804YankeeFan]

If all the electrical energy is gone, wont the charges stop moving?

[Steve4Physics]

@804YankeeFan

Its a continuous process. Electrical energy is delivered at a steady rate over a period of time. The battery is acting like a steady pump, pumping electrons around the circuit. But of course, when the battery is dead, the electrons 'stop moving'.

[ThreeSaggyBollocks]

@Steve4Physics No they don't, electrons are always vibrating.

[Steve4Physics]

@ThreeSaggyBollocks . Hi. You are correct: electrons are always subject to random thermal motion. The effect is small but can be measured and produces what is called 'Johnson-Nyquist noise'. But at this introductory level, this was not something that I wanted to address.

[SalmanBacha]

Sir tell me that voltage is in cicuit and emf is inside the battery between the two plates of battery and doing work on a charge in moving it from negative plate towards the positive plate inside the battery and voltage moves a charge from positive to negative plate outside the battery means in the circuit.Am i right Sir?

[Steve4Physics]

@SalmanBacha

Hi. Some of your explanation is OK providing you have no internal resistance in the battery. But your description of the way charges move is wrong.

Here in the UK some of what you said is OK for GCSE (e.g. under 16 years old) but not for A-level (e.g. over 16 years old), as it does not allow for internal resistance. I have emailed you an explanation via your channel; I hope it helps you. Try reading about internal resistance.

Good luck

Steve

[Steve4Physics]

@SalmanBacha

Hi. Some of your explanation is OK providing you have no internal resistance in the battery. But your description of the way charges move is wrong.

Here in the UK some of what you said is OK for GCSE (e.g. under 16 years old) but not for A-level (e.g. over 16 years old), as it does not allow for internal resistance. I have emailed you an explanation via your channel; I hope it helps you. Try reading about internal resistance.

Good luck

Steve

[SalmanBacha]

@Steve4Physics Thnx Sir and i know that emf is not force,its work done on a charge in moving it from negative plate towards the positive plate inside the battery,and the resistance that the charge faces inside the batery while moving from negative to positive plate is called internal resistance?Is it a right concept?Or emf is the energy generated by the chemical present inside the battery?So tell me that emf is inside the battery or it is in the circuit and voltage inside battery ?

[Steve4Physics]

@SalmanBacha

Emf is always inside the battery (or generator, or photcell, etc.).

In a simple situation (no internal resistance) voltage is outside the battery.

But if there is internal resistance, there also a voltage drop inside the battery which must be subtracted from the emf.

[SalmanBacha]

@Steve4Physics Oh thanks alot Sir i was just wishing this answer u given to me in this comment.Thanx

[therealjordiano]

You make it pretty clear man :) thanks... one question though, are coulombs a unit measuring charge.. or what? :|

[Steve4Physics]

@therealjordiano

Hi therealjordiano. Yes the coulomb (C) is a unit for measuring amounts of charge.

E.g. the electron has a charge of -1.6x10^-19C.

For background info' on charge and current watch:

GCE (A level) Physics E01Charge and Current. Part 1 of 2

(Sorry can't give the link, as YouTube blocks urls in comments.)

[shield543]

This is a really good explanation of e.m.f. I had always heard "emf" but never really knew what it was, I just knew the maths. Thanks for explaining that, really helpful :)

[Steve4Physics]

Not everyone doing A-level finds the material straight forward, so I deliberately went slowly enough to try to make it clear to a wide range of abilities. I've found that students - even with very good O-level/GCSE grades- often don't understand the basics. If you are already partly familiar with and understand, the material, it will definitely seem too slow/long! You can't please all the people all the time!

[Twisted666Freak]

nice video !!

but Considering u made them for A level !!!!

ur explaining one thing too many times !!!

I mean it was ok if this was for olevel

But for alevel nah....

its too long !!!

25 mins just to understand diff bw EMF AND PD !!!!! to much

[donatellomusketeers]

@Twisted666Freak If your so clever then dont whatch the videos. When you upload a better explination then i think you can comment

[Twisted666Freak]

@donatellomusketeers i dint mean to offend anyone mate !! theres no need to be angry !!! All i said was its a bit too long. I wrote there that the video is nice,and its helpful,however it shouldnt be labled as A LEVEL explaination !! Cause dude if ur doing A level u do need to know basic stuff like V=IR and I=V/R i mean like he was showing changing the formula !!! I do respect the fact he took the innitiative,i was just giving an opinion. Everyone has a right to opinion. :D GUDLUK 4 2mrw

[heavymetaldeath4life]

@Twisted666Freak Hey, so we don't actually need to know all of that for tomorrow? Great. By the way, how do you revise for waves?

[Twisted666Freak]

@heavymetaldeath4life

We do,but its like this is something we learnt back in grade 9 !!!

tomrrow ?!?!? i have my exam in 6hrs :D !!!

Youtube !!!! Aslwell !!

[aassasin19]

thanks a lot dude you made it simpler ... useful for o levelers as well...

[vilandes]

Thanks dude very helpful :)

[JP8940]

Thanks I never understood the difference between emf and voltage

[Steve4Physics]

Thanks Tuvia. For information, note that a 'curly E' is a capital E from the the 'Script' font.

A Greek letter epsilon look like:

ε (lower case)

E (upper case).

[TuviaGering]

thank you so much for the explanation! by the way the "curly E" is called epsilon from greek alphabet

[remiwarren]

You damn right its helpful! Thank you sir!

[Steve4Physics]

Thanks MrRyanification. I'll be adding more, as time permits.

[MrRyanification]

Thank you. I've always found electrical circuits confusing, this makes sense now.