Potential Difference vs. Electromotive Force - A Level Physics

This video explains the differences between potential difference and electromotive force for A Level Physics.
This is where it gets tricky! You may previously have used the term 'voltage' but now you need to understand the difference between the e.m.f. of a supply and the p.d. across a component. This also shows you where to put a voltmeter in a circuit and the definitions of all key terms. Please note that this analogy is not perfect, it doesn't really explain how energy can be transferred almost instantaneously or how alternating current works but it's a start.
Electromotive Force: The energy gained per unit charge by charges passing through a supply (from chemical to electrical).
Potential Difference: The energy lost per unit charge by charges passing through a component (from electrical to other forms).
Thanks for watching,
Lewis
This video is recommended for anyone studying A Level Physics in the following exam boards:
AQA
CIE
Edexcel
Edexcel IAL
Eduqas
IB
OCR A
OCR B
WJEC
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[@fj19981]

This explanation is 100x better than my high school teacher

[@Mirsab]

How could I ever thank you enough, I finally understood Emf. and P.d. And I'm 19, been through school and so much, but I guess all it required was some unorthodox explanation using Legos 😂👌🏼

[@rahulmawa5149]

really loved the way you showed it with the help of lego,you made it easier and way more polite(in some ways)

[@princessofproductivity]

What a legend. Everyone else’s explanation is over complicated. Yours is intuitive and complete. Perfect, thank you !

[@rakshithkakunje621]

Thank you so much this helped me understand this concept better than 4 other teachers who had taught me this.

[@PhysicsOnline]

Thank you!

[@muhammadabdullahwaseem3040]

I wish more teachers were like you. Thanks a lot for this explanation

[@hehehee7317]

Words simply cannot express my gratitude. Thanks for your wonderful analogy and succinct explanation.

[@PhysicsOnline]

You're very welcome

[@annonymousannonymous599]

HOLY SHIT IN THAT SPAN OF 6 MIN I LEARNT MORE THAN WHAT I HAVE FROM HOURS OF READING MY TEXTBOOK THANK YOU SO MUCH

[@SteffiMendes]

All I could think about the entire video is how similar you sound to Josh from the Sidemen. Great video!

[@mine_crafter2403]

Oh yeah

[@jasonsolomons2574]

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[@raghadayman4381]

your explanation are clear and so helpful; thank you so much I don't know what would i have done without them.

[@PhysicsOnline]

Between 5.00 and 5.03 I said it must go in parallel with the component in the circuit.

[@azoulali4029]

How?

[@joshuaarnold8579]

You should pin this comment. And your videos are great :)

[@adnan5776]

Magnificent effort for better grasping.........1000 salutes and of course thank you...

[@abdulazizalharbi6228]

What a great explanation, the problem is, people always treat EMF and Potential Difference as one thing (Voltage), which makes electricity hard to understand and you feel there is a contradiction. (Ex: they always say that when we have a close circuit we have hight current + voltage is the thing that makes electrons move which means if there is no voltage so there is no current, but in a close circuit as I mentioned the current is very hight but they say the voltage will be 0 !! how we will have current then? but what they mean is we still have EMF the electrons are loaded with energy, but the electrons with a close circuit do not drop this energy since there is no load (which means there is no potential difference, potential difference = 0) and they use Voltage here instead of potential difference.

[@dayledonne8272]

These videos are superb, keep them coming!

[@FaithSamuel_00]

Finally I get it, cheers boss!

[@procrastinatingproductivel2031]

i thought it was hard.... but you made it very simple... don't know how to thank you.... god bless you!❤❤❤❤❤ THANK YOU SOOO MUCH!

[@avinash6427]

Very good way of visualizing it..thnx dude

[@PhysicsOnline]

Glad you liked it!

[@siddiki9778]

Very nice explanation. Thanks for the video!!

[@rhythmandacoustics]

Does the distinction actually matter? One is just voltage source and the other the voltage drop. By definition the potential difference between two points is the voltage. The source anode and cathod has voltage and when the circuit is completed the full voltage of the source goes to the load.

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Am always watching ti's before schl

[@peterliu5712]

Videos are excellent.Can you make a summary for all the a level physics definitions that need to be memorized, thank you very much.Wish your channel to be better and better.

[@bunty3798]

Very understanding way to explain. Got the idea. The major difference is that the emf is always higher than the potential difference in the ckt what i came to understand from this video. Thanks a lot

[@PritikaShrestha]

Thank you so much for this innovative idea.

[@afisatisha3135]

Thankyou for your explanation...after 3day of my heard work finally with the help of your video i have cleared may concept:)

[@arshisid47]

Absolutely wonderful video. Easy to understand analogy. Clears my concept very much. Thank you!

[@AakashSawant001]

good attempt to explain the concept

[@dougdoug2165]

PD is what we were taught as voltage drop back in the dark ages.

[@DemetriLoizou]

Brilliant explanation! Thanks!

[@yunguncletracksinc.6996]

thank you this was a great help been stressing for a while and you helped me out !!!!!!!!!!!!

[@thiccteletubby1234]

very sick my guy

[@dalia4289]

i was really confused about it and was mixing them up thank you for your effort of explaining

[@AKSHAY-hk2tt]

wonderful video

[@goat6030]

I am 14 and This was so helpful thanks a lot

[@arundir6485]

Wow great vid and explanation. Thanks

[@deviprasadalapati2184]

Well explained. Thank you.

[@ronelpanchoo3969]

This explanation is absolutely brilliant !

[@alexhamzelou5106]

these videos are absoluetly brilliant

[@PhysicsOnline]

Thank you - there are now over 500!

[@joannadaniel9396]

thank you

[@rufikunbargi9407]

This is so good! Thank you.

[@user-sq4uy1gi3n]

Excellent explanation!!

[@bern1223]

I love you so much for using Legos to help me understand this. Thank you Lewis!

[@user-ew4wq9qi6x]

It's sooo cuteee I can't!!! But the explanation was excellent! Thank youuuu

[@_A_TruongNhaNguyen]

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[@nikitachaudhari8443]

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[@Listenme3249]

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[@PhysicsOnline]

Thank you! 😃

[@farhaadfarhaad497]

Hi dear Lewis . Thank you for your video . As far as I have learned , electrons ( charge carriers ) do not move so far through a wire. In fact electrons move a very short distance . They actually transfer their electrical field to one another and they move only few centimeters. No electron leaves the conductor . For example in a wire of 1 meter long it may never happen that an electron reaches from one head to the other , because they have a back and forth movement . Is this right ? thanks again for your video .

[@Sxlanki._x]

farthead farthead

[@farhaadfarhaad497]

Let me ask another question I've always had. If we connect only one (positive) head of a power supply to a conductor ,What will happen? I mean what exactly do electrons do ?. Do they still start moving toward the other end of the wire ? Do they accumulate somewhere id. on one end of the wire or what ? Do they receive the electrical field from the power supply and keep transferring it to each other ? thank you

[@annabellewilson8825]

BEST VIDEO EVER

[@PhysicsOnline]

Thanks!

[@kirtisha0310]

Amazing

[@spaxceghost]

Bro thank u so much great explanation 😍

[@abdullahbinuzair1685]

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[@TheFemalePhysicist]

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[@ninives]

Thanks mate now i get it, great explanation.

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[@PhysicsOnline]

+ModdersApprentice Thanks - hope they're useful.

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[@STP31]

Thank you so so much

[@JimbobFaz]

So will the e.m.f provided by the battery have an opposite sign to the p.d measured across the component? Furthermore, if the e.m.f from the battery had exactly the same magnitude as the p.d measured across the component, would the current be zero? That is, the system would be in equilibrium?

[@timeisallitis]

yes i got that...thanks bro

[@samuelj5890]

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[@luckycat3764]

Very very nice electrical physics was never this much interesting

[@janamohammed6775]

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[@bmxphilosophy9805]

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Thanks abut 🔥🔥🔥🔥🔥

[@NabMindful]

I do Leaving Cert Physics in Ireland and this is similar to what we learn found it hard to grasp but it’s way easier now thanks!!

[@MrNakedWizard]

Thank you

[@MAyub-fq8pj]

I would really love if you could explain the development of higher and lower potentials inside the source of emf. Thank u and really helpful explanation.

[@mirsabn5982]

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[@madhurar4599]

Thank you sir

[@spacesuitred3839]

very good explanation! keep going...

[@PhysicsOnline]

Thanks

[@arnie6605]

Can we say that the electromotive force transfers other forms of energy to electrical or do we have to state that it's chemical

[@busboijamz7191]

I needed this.

[@grkreddy4460]

Thanks sir 🙏

[@salbts2101]

I wanna ask a question. When we measure potential difference, the positive end of battery is connected to positive end of voltmeter, in measuremnet of current, positive of battery is connected to positive of ammeter but in emf it is opposite? Can u plz explain this. shouldn't positive ends be connected to negative for flow of charge???

[@methasawijayasuriya6472]

does it mean that if we connected a voltmeter to a closed circuit with no electrical appliance connected, it will show zero?

[@PhysicsOnline]

Yes

[@methasawijayasuriya6472]

thanks

[@kundandahal766]

can u say why the value of emf and pd are different in this interpretation.?

[@Gamemaster8167]

Just had the biggest click I ever had to understand Potential diffference, while watching this. Thank you so much

[@PhysicsOnline]

Not a problem - it's great when those moments happen and all becomes clear,

[@user-hu7su4kh4q]

You are talking about "charged particles" movement and "current flow", but as i know the only particles that move are electrons making the current flow. So what are these "charged particles" ?

[@PhysicsOnline]

Electrons

[@mohammadelkhatib5038]

How is that , you say emf and pd is energy , while we measure them in Volts

[@abdullahraheel8269]

it was an awesome video but can some one explain at what happens at the atomic level ? i mean does electrons get excited or something?

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Your channel ad came up before this video 😂

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dies from peak physics

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[@sppremsarimella4915]

Very interesting

[@umartaher5000]

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[@asmae6869]

Thank you sir for the video! I was thinking that the electromotive force was the force necessary to push the electrons in the circuit, but I wonder now how the electrons can keep moving after releasing all the energy to the bulb (in this example). I don't understand.

[@suicidalducks1822]

Electrons aren't moved by energy they move because they are attracted to the positive terminal of each component in the circuit. This is current - the flow of charge carriers from one terminal to another of opposite charge.

[@themediumcheese7484]

Wouldn't it be more correct to say that the electrical energy becomes vibrational kinetic energy in the atoms, which causes it to radiate thermal energy and light?

[@jakkuwolfinsomnia8058]

If electromotive force by definition is the rate of energy transferred from chemical to electrical energy per unit charge. Why is it not considered in terms of being a force?

[@waynemaracle7139]

very good

[@barashraim8113]

Hello Sir, Thanks for this helpful video. But I did not understand what you said between 5:00 and 5:03 where you say " and in order for it to "something" part of the circuit " . What is the word you said mean and what is it?

[@tobias-edwards]

'basically have no' ^^

[@nedowen723]

Mate, thankyou

[@akvlogs_1-i7k]

nice wow!!!!!!!!!!!!!!!!!!

[@MOI-su4lx]

2:37 isn't he supposed to walk in the other direction from negative to positive

[@ahmadsajeel]

love it

[@Zheng0211]

4:30

[@richardfeynman7332]

Still i dont get the difference...

[@DXPAlien]

Current is the flow of charge per second, but what is charge? I mean i know it's Q= IT, but what is this charge? and If current is the flow of charge then what causes the current i mean what is that thing that carries the charge? are the charge carries some actual particle that carries the charge?

[@PhysicsOnline]

Onim Dip Charge is a property that some particles have, just like most particles have a property called mass.