SPEAKER 1: Check

out this capacitor. Look at what happens if I

hook it up to this light bulb. CHILDREN (IN UNISON): Boo! SPEAKER 1: Yeah,

nothing happened because the capacitor

is not charged up. But if we look at up

to a battery first, to charge up the capacitor,

and then hook it up to the light bulb, the

light bulb lights up. CHILDREN (IN UNISON): Ooh! SPEAKER 1: The

reason this happens is because when a capacitor is

charged up, it not only stores charge, but it stores

energy as well. When we hooked up the

capacitor to the battery, the charges got separated. These separated charges

want to come back together when given the chance,

because opposites attract. So if you complete the

circuit with some wires and a light bulb,

currents going to flow. And the energy that was

stored in the capacitor turns into light and heat that

comes out of the light bulb. Once the capacitor

discharges itself, and there’s no more

charges left to transfer, the process stops and

the light goes out. The type of energy that’s

stored in capacitors is electrical potential energy. So if we want to figure

out how much energy is stored in a

capacitor, we need to remind ourselves

what the formula is for electrical potential energy. If a charge, Q, moves

through a voltage, V, the change in electrical

potential energy of that charge is just Q times V. Looking

at this formula, what do you think the energy would

be of a capacitor that’s been charged up to a

charge Q, and a voltage V? CHILDREN (IN UNISON): Q times V! SPEAKER 1: Yeah, and that’s what

I thought it would have been, too. But it turns out the energy of

a capacitor is 1/2 Q times V. CHILDREN (IN UNISON): Boo! SPEAKER 1: Where does

this 1/2 come from? How come the energy

is not just Q times V? Well, the energy of

a capacitor would be Q times V if during

discharge, all of the charges were to drop through the

total initial voltage, V. But during discharge,

all of the charges won’t drop through

the total voltage, V. In fact, only the first

charge that gets transferred is going to drop through the

total initial voltage, V. All of the charges that get

transferred after that are going to drop through

less and less voltage. The reason for this is that

each time a charge gets transferred it decreases

the total amount of charge stored on the capacitor. And as the charge on the

capacitor keeps decreasing, the voltage of the

capacitor keeps decreasing. Remember that the

capacitance is defined to be the charge stored

on a capacitor divided by the voltage across

that capacitor. So as the charge goes down,

the voltage goes down. As more and more charge

gets transferred, there’ll be a point

where a charge only drops through 3/4 of

the initial voltage. Wait longer, and

there’ll come a time when a charge gets transferred

through only a half of the initial voltage. Wait even longer, and

a charge will only get transferred through a

fourth of the initial voltage. And the last charge to

get transferred drops through almost no

voltage at all, because there’s

basically no charge left that’s stored

on the capacitor. If you were to add

up all of these drops in electrical

potential energy, you’d find that the total drop

in energy of the capacitor is just Q, the total

charge that was initially on the capacitor, times

1/2 the initial voltage of the capacitor. So basically that 1/2 is there

because not all the charge dropped through the total

initial voltage, V. On average, the charges dropped through

only a half the initial voltage. So if you take the charge stored

on a capacitor at any moment, and multiply by the voltage

across the capacitor at that same

moment, divide by 2, you’ll have the energy

stored on the capacitor at that particular moment. There’s another form of this

equation that can be useful. Since capacitance is defined

to be charge over voltage, we can rewrite this

as charge equals capacitance times voltage. If we substitute the

capacitance times voltage in for the charge, we see

that the energy of a capacitor can also be written as 1/2

times the capacitance times the voltage across

the capacitor squared. But now we have a problem. In one of these formulas

the V is squared, and in one of these formulas

the V a not squared. I used to have trouble

remembering which is which. But here’s how I remember now. If you use the formula

with the C in it, then you can see the V squared. And if you use the formula

that doesn’t have the C in it, then you can’t

see the V squared. So these are the two

formulas for the energy stored in a capacitor. But you have to be careful. The voltage, V,

in these formulas refers to the voltage

across the capacitor. It’s not necessarily the voltage

of the battery in the problem. If you’re just looking

at the simplest case of one battery that

has fully charged up a single capacitor,

then in that case, the voltage across

the capacitor will be the same as the

voltage of the battery. So if a 9-volt battery

has charges up a capacitor to a maximum charge

of four coulombs, then the energy stored

by the capacitor is going to be 18 joules. Because the voltage

across the capacitor is going to be the same as

the voltage of the battery. But if you’re looking at a case

where multiple batteries are hooked up to

multiple capacitors, then in order to find the

energy of a single capacitor, you’ve got to use

the voltage across that particular capacitor. In other words, if you

were given this circuit with these values, you

could determine the energy stored in the middle

capacitor by using 1/2 Q-V. You would just have

to be careful to use the voltage of that

capacitor, and not the voltage of the battery. Plugging in five

coulombs for the charge lets you figure out that

the energy is 7.5 joules. CHILDREN (IN UNISON): Ooh! [MUSIC PLAYING]

very helpful & nice presentation

, thanks

Brilliant.

Great Vid! Easy to follow! Probably the best i've see so far

Very Well Work On the Education, Keep Going On ,, Never Stop ………………..

very good..

you just got to love these videos

It's like a combination of high school physics and Blues Clues

Helped me a lot 🆒🆒🆒🆒🆒🆒🆒🆒

The best teaching videos. Thanks professor, I admire this great system of teaching experience.

Nice video. I am trying to charge up a capacitor with 2200 uF -400V specs but it only charges up like 0.1 V per sec. This is going to take too long for me to get to -400 V or even 280 V. How else can i increase the amount of energy flowing into the capacitor so then i can get at least 280 V into the capacitor?

nice one

How electrons goes over that dielectric medium

1/2CV^2 looks like the solution to a differential equation?

What does he mean a charge ''drops through" the voltage?

finally , i understood how capacitors work. Thank you so much for this helpful lessons

charged up…… no drake

I think it's better to use U instead of E (Energy) in the video, it's a little bit confusing

So why is this uploaded on a medical channel again?>

Who is this amazing individual?

very good.

2 the parallel capacitor is fully charged then the charge. then take the power out, the charge in two copies will look like?

oooooooooooooooooooooooooooooooooooooooooooooooooooo hahahahaha those kids 😀

Pls turn off that sound! Its so annoying..

The way he made us remember those formulas!!!!HAHAHA

This video is PERFECT!

Thanks a lot!

Very detailed and precise.

kid's

………………..9cccc

I think this is like relationships. Opposites attract, then little by little the capacitance (dopamine/love/attraction) is less every time you charge (hang) the capacitor (the relationship).

informative video keep it up ..TQ

Very informative. Keep this good work up

I want lessons of Ac by David Santo Pietro with the music before end of Dec plz

thanks a lot for your effort ….it was really useful, but try to get rid of those children next time :))

Quality video. Do you have one on capacitors charging with constant current?

woohoo…..best

Thank you – great video. Quick question: can someone please explain how the voltages were calculated in the final section? Adding up the voltages along one route gives 10.5V but the PD of the supply is 10V? Thanks

what happens when to energy variation when dielectrics used

awesome..😍

DAT sound effects tho

This dude deserves a nobel prize in teaching

At 2:55 he shows that as the voltage decreases as does the charge but i thought the capacitance is independent of the voltage and charge? or is he only showing the relationship between voltage and charge? someone explain please

best physics teacher in the world

i love these videos…

yu r awesome

I'm liking this for the C pun

This is very amusing yet very helpful and simple to understand. Thanks a lot!

When he said hooked up i cringed each time lol

OMG superb.

See technique to learn formula is a bt funny hahahahahaha

Eminem

Oooh!

Nice tutorial!

that background music is mesmerizing

Why don't they make capacitors with tiny LED, so when they get hot the turn the led blue light on, so it prevents the overheating

this is very helpful 🙂 and interesting to hear. it was like listening to a rap song. 😀

Sir, You are God !!

What kind of odd death grip is he using on that pen????

Good shit!

My Physics II textbook doesn't explain well where the 1/2 comes from. This covered it perfectly!

Thank You. You explained in 6 min what my Physics teacher took a week to explain.

Isn’t Energy stored in a capacitor

Q^2/2C ????

love u

Bro.. These videos are SO good. With the real life examples and super thorough explanations and tips. I appreciate this a lot. Physics is not as scary now… Thank you so much!! I had to go on the youtube page for these vids from the khan website just to click like!

Best explanation on EARTH 🌏

Why are the children shouting boo and ooh?

👌

Those kids are fukin annoying

Music's a tad annoying

YOUR VIDEOS SOUND LIKE A RAP IN PHYSICS!!!!!!!!!!!!!!!

Current doesn't flow its the charge that's flow

It holds charge and energy? So I have a dick and a penis?

what is the background music?

Does the capacitor pushes the amps that the load needs or more then then it requires?

for example if we take plates made up of copper, after a capacitor charged, will plates of capacitor turns to Cu+(positively charged plate) and Cu-(negatively charged plate) or capacitor plates remains same as Cu?

This man is a genius.

السلام عليكم

الترجمة الخاصة بهذا الدرس كاملة ممكن إي شخص يدخل على إضافة لغة جديدة و ثم يقيّم الترجمة كي تتم إضافتها 😊 و تصبح متاحة بشكل مباشر 😳

What is the difference between a battery and a capacitor ?

awwwwwsome

Why does he use E for energy. Confused the fuck outta me

Love it

Amazingly executed as well as mind blowing nd interesting

What if capacitors have unequal number of charges!?? It can't happen in capacitor charged by battery but I talk about the capacitors used as electrodes in biomedical sensors such as ECG.

How we calculate voltage then!??

6.25V+3V+1.25>1+9???

why so serious😏😏😏😏

Can someone please explain to me how at 6:20 the voltages add up to 10 volts? They should right?

AMAZING video

The ohhhhhhh was funny lol

I love the bgm

Will charging the capacitor put a drain on the battery ?

well, in one of my books while reading about capacitance. There was a topic that when an uncharged conductor is brought near a charged conductor, it leads to a decrease in Potential of the charged conductor which decreases the Capacitance.

But in some other book, I read that Capacitance doesn't depend upon q and V.

What's the correct explanation?

great video! but for the last example, shouldn't the voltages be 10V (1+9) according to the batteries? But the voltage in that circuit was actually 10.5V (6.25+3+1.25)?

u r amazing , man .. keep going

what if the circuit is parallel? do we use the same equation?

The background music is super fly lol

what's those Ooooo coming up all of a sudden 😂😂😂😂

3:24 what does it really mean that ‘charge drops through no voltage at all’???

Studying for the MCAT right now. I wish I had learned this in High School or Undergrad.

Please make videos in hindi so we will learn easily

Hats off

What a explanation

I found in Uni that the voltage across the capacitor gets written as dv (dielectric voltage), which is to differentiate the voltage across it from the voltage of the battery. But i hate writing it out cause the formula then looks like E = 1/2Cdv^2, and since high school i kept seeing “d” as for distance. This then gets added to other equations like capacitor current (i = CV/t) into i = cdv/dt. It gets so frustrating.

man!the way you teach us,is just..perfect…wish our teachers had this ability too.

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