Magnetic force on a charge | Physics

Magnetic force on a charge | Physics | Khan Academy

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16 жыл бұрын

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Sal shows how to find the size and direction of the magnetic force using F=qvB and the right hand rule. Created by Sal Khan.
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Пікірлер: 157

@dxvxm335 3 жыл бұрын

Crazy to think people 10 years ago were cramming exactly how i am a decade later. Makes you wonder where everyone is now.

@Flix-Echo Жыл бұрын

Bro i am 14

@sarangtamirisa5090 Жыл бұрын

some of us still loving physics and working in various fields of engineering. Revisiting these topics because a neighbor kid wanted me to explain magnetism to him

@khanacademy 16 жыл бұрын

It did seem to disappear. Don't know how that happened. I now added it back to the physics playlist right before this video.

@amijan2014 4 жыл бұрын

2020 anyone?

@janaj2003 3 жыл бұрын

yep

@prabeeshranatimsina8259 3 жыл бұрын

I m

@southsidedough 3 жыл бұрын

Physics 2 exam coming up

@andriivladyka4359 3 жыл бұрын

2021, actually.

@trickingwithjordan1708 3 жыл бұрын

@user-ey6kg9od7z 3 ай бұрын

here i am after completing my studies, i find my self at my job refreshing my mind on this topic, you truly have helped millions, you should be awarded with nobel prize for how many people you have helped.

@zelta_adventures2544 8 жыл бұрын

Thanks for existing 🙌🏼🙏🏼🙏🏼

@ignantxxxninja 3 жыл бұрын

I'm taking calc 3 and non-calc-based physics 2, and this makes it so much more understandable.

@BlackOfTheNight 12 жыл бұрын

holy crap the transcribed audio (CC) thingy actually works for his videos!

@glendonchumawar9276 3 жыл бұрын

these videos are still saving students

@calicoesblue4703 2 жыл бұрын

Yep 👍

@boradokaye7930 7 жыл бұрын

thank you so much

@mukeshkumar-sl4wu 11 жыл бұрын

nice lecture

@jayprakashgogoi 3 жыл бұрын

2021

@T1MHughes 13 жыл бұрын

Sal, should your definition of the magnitude of the vector force, F, at 6:30, not be in terms of the magnitude of the charge, |Q|, and not simply Q? Since Q can clearly take positive and negative values (owing to positive and negative charges), not considering it's magnitude would imply that the force magnitude could take negative values.

@jimmyti9cer 12 жыл бұрын

@dfdf03 i live in California USA and my fundamentals of physics textbook does magnetism at chapter 30. It comes after the electric fields, electrostatics, and currents (EMF, transformers, circuit loops) magnetism comes after all of that for our class anyway.

@flixx82 4 жыл бұрын

this dude studers so much

@ollieoniel 13 жыл бұрын

How does a magnet drop in strength is it to the 4th or the 3rd power? Also with 2 wires does it drop off at the 2nd power and is it the 3rd power with a magnet? Also in a sphere that has north facing in and south facing out does it act as magnet since there is no return path of the field?

@mariagallent4981 6 жыл бұрын

This says it includes the right hand rule, but there is no mention of it

@woodmannakupa6037 5 жыл бұрын

Interesting

@murderofcrows804 6 жыл бұрын

Does the shape of a man made magnet result in stronger levels of magnetism. I was thinking that if a field is variant that is there were less awkward shapes like a flat circle or a square or rectangle. A solid sphere would have a greater magnetic perfection?

@Hey-Parth 3 жыл бұрын

Amazing

@Richard_is_cool 9 жыл бұрын

it doesn't have to be perpendicular for the cross product to make sense, just need to not be parallel

@Rockyzach88 7 жыл бұрын

Technically since cross product is equivalent to |a||b|sin(theta), you still are only accounting for the perpendicular component of the vector as that is what |b|sin(theta) gives you mathematically/geometrically.

@Rockyzach88 7 жыл бұрын

Times n(unit vector perpendicular to the plane of a and b) of course so you get a vector back.

@chisomodimmegwa3479 7 жыл бұрын

Rockyzach88, Richard S is right, this formular he is using is used in centripetal force

@godlesssss 13 жыл бұрын

If the atoms are all in alignment and spinning; could the magnetic force be a result of the centrifical force of the spinning atoms?

@kwong28 6 жыл бұрын

Thanks

@BloodyOathMate11 12 жыл бұрын

on ya SAL! your the reason i am sort of scraping by year 12 Physics!

@karman103batth4 2 жыл бұрын

I am really curious where did life take you after 9 years

@tihamichy 2 жыл бұрын

@@karman103batth4 Same here

@slothguy5716 7 жыл бұрын

Your diagram of the field lines is way elongated. Your compass needle needle wasn't even close to the north lol.

@ajskilton 14 жыл бұрын

why is the direction of the cross product of two vectors a right handed screw 'into the paper' and not in the opposite direction? I am of course refering in particular to F=Q(VXB) so my question is really why the force here is not in the opposite direction? I know it's just the way nature is but WHY??

@sanchi7410 2 жыл бұрын

The fact that this was 13yrs ago😳

@MysteryofScience 5 жыл бұрын

i was 10years old when this video is uploaded

@Soumyajit_Roy 3 жыл бұрын

2021 anyone? If yes don't just see comments 😂 focus.

@joycetui6737 4 жыл бұрын

This is more Interesting 😅😆 it

@AlanMorales502 11 жыл бұрын

so force is newtons, charge is coulombs, velocity is meters per second and this is the fffffb-units

@BoburmanGaming 7 жыл бұрын

Everything Falls in 9.8 meters per to the 2nd

@shivangb237 6 жыл бұрын

Actually magnetic field si unit is tesla

@lalalanding234 Жыл бұрын

Yo!!!! My fave thq

@taqwatoqee5016 6 жыл бұрын

Omg the only thing that surprised me that this video is about 10 years ago .. Woow o,o

@Jeid0Zen 8 жыл бұрын

Thank u this video helps me so much

@T1MHughes 13 жыл бұрын

Sal, should your definition of the magnitude of the force at 6:30 not include the magnitude of the charge, |Q|, not simply Q? If you do not take the magnitude then the magnitude of F is permitted to be negative since Q clearly takes both positive and negative values (from positive and negative charges).

@Chad-lg9vx 7 ай бұрын

Bro commented this in 2011 smth man .. hey how are u rn ( just wanted to talk to someone with old comments like this )

@TheOneToxic 13 жыл бұрын

One person belives that science does not exits

@joycetui6737 4 жыл бұрын

That is a fool

@GenericCoder 12 жыл бұрын

@GenericCoder add youtube and remove the spaces

@MrSaad1932 12 жыл бұрын

i think the unit for B is teslas...

@Mr.Lego77 15 жыл бұрын

this one is complicated...i am not that good with symbols and numbers...i liked it when it was with drawings and illustrations...I could easily understood what's going on!

@morriganishmael4153 6 жыл бұрын

At 0.30 to 1.00ish, they talk about magnetic field lines being the "movement of a magnetic north monopole", which isn't really accurate. The example of a compass needle's direction being tangent to the field line is the more accurate explanation.

@calicoesblue4703 2 жыл бұрын

Magnetic force does not move

@MyCheesebrain 12 жыл бұрын

Oh what would I do w/o Khan?

@marvhartigan3677 3 жыл бұрын

haha me toooo!!

@TeKNiQ50 12 жыл бұрын

The ghost of Khanacademy did it.

@vrdesk 13 жыл бұрын

@villebacker LOL

@gargameliuss 14 жыл бұрын

Why there is no more a video? :( Is there anything like a CD/DVD of Khan videos?

@FarshidBayat 12 жыл бұрын

"A magnetic field in order to have an effect on a charge has to be perpendicular to its velocity", are you sure about this? I mean its possible to take the cross product of two non parallel vectors. I think the only time when a magnetic field doesnt have an effect is when the charge isnt moving or is moving at an angle such that sinx = 0, right?

@abhaychandra2624 3 жыл бұрын

The effect of the magnetic field will be maximum if the velocity of charge is perpendicular to the magnetic field. For angle other than 90 degree there is sin theta. Also you are right if the charge is moving parallel to the magnetic field show the angle is zero or 180 degree, thus their sine will be zero thus making the force is zero

@mivapusa 6 жыл бұрын

What confuddled me for the longest time is I thought he was writing beta instead of just B and referring to something entirely else

@villebacker 13 жыл бұрын

Subtitles --> 4:37

@raymin5619 3 жыл бұрын

what does it say? i think they changed the subs after so many years.

@ehmoudfahmy2332 Жыл бұрын

I hope you answer my questions what is the proton charge in magnesium posatefe charge is it protons wev

@risklife4527 4 жыл бұрын

How do I find the magnitude

@deepikashukla3027 4 жыл бұрын

I was born when this video uploaded

@abhirupsaha2803 4 жыл бұрын

You're 11 why are you watching this

@adahwilke4109 4 жыл бұрын

I was 2 when it was lol im 14 now

@averagemilffan 4 жыл бұрын

@@abhirupsaha2803 why shouldn't be if he is interested in science he will

@shobarbaba 4 жыл бұрын

i was four not that anyone cares...

@stas1ee7 14 жыл бұрын

@ajskilton it does not really matter. it's just a math trick.

@mohansundarmadurai1933 5 жыл бұрын

But why f = QvB

@parru030 12 жыл бұрын

have you ever thing there is more than 3 dimension ?

@blakezabala3846 6 жыл бұрын

Fix your question so it can be answered

@conditionalbee9603 4 жыл бұрын

I'm 8 years late but yeah, I think there are more than 3 dimensions. We just can't comprehend it.

@piyalsana6169 Жыл бұрын

2023

@grantstidham9322 4 жыл бұрын

B units are Teslas

@manjeetrathee9035 3 жыл бұрын

Please make your videos in hindi

@calvinhobbesliker2 15 жыл бұрын

couldn't the units be written as kg/Cs?

@thetruth45678 8 жыл бұрын

There's no such thing as "lines of force" in any field. The force is not confined to lines, even if iron filings seem to be. To prove this, place one iron filing next to the magnetic source, and try to detect the individual force lines. You won't find any. The filing will not adhere more or less to any spot around the magnet, unless it get close enough to get pulled to the magnet's surface, but even then, it's not stuck to a spot on the surface, but is held equally strongly at any point on the surface. Flux lines are an imaginary model invented by man to conceptualize the field, and nothing more.

@calicoesblue4703 2 жыл бұрын

You have any articles that confirm what you are saying?

@thetruth45678 2 жыл бұрын

@@calicoesblue4703 I told you how to confirm it for yourself. If you don't trust my words, why would some other author's words convince you? Just grab a magnet and test it yourself. Quit waiting for someone to tell you what to think, and find out the truth yourself.

@jimmyti9cer 12 жыл бұрын

Tesla...a deserving fellow...hahaha yeah to say the least

@kevinpatty119 4 жыл бұрын

a deserving? more like an absolute genius!

@Nodoybefore 12 жыл бұрын

Nikola Tesla- theres not "i" at the end, sal :)

@ignantxxxninja 3 жыл бұрын

wait, so the North is actually facing the south magnetic pole?

@FEATHEREDNEW 12 жыл бұрын

magnetic field.. i think

@dzMonsterr23 12 жыл бұрын

the 2 ppl who disliked this are physics teaches who are not as smart as this guy

@TheComicalUsername 8 жыл бұрын

NIKOLA tesla, not Nikolai! good vid tho

@zlxpanda4746 4 жыл бұрын

What is B

@livelikelegends2411 3 жыл бұрын

Any one in 2021 😊

@dmlinares 11 жыл бұрын

i had it before i got here

@madmin0904 15 жыл бұрын

5 star youtube video. Truly.

@cp12298 3 жыл бұрын

Are you alive sir?

@FarshidBayat 12 жыл бұрын

"two non perpendicular vectors" my bad

@wEsTsIdE732 12 жыл бұрын

LATE NIGHT CRAMMING

@marvolotom 13 жыл бұрын

in germany monopoles were created

@calicoesblue4703 2 жыл бұрын

This is a misconception. A magnetic field is not just an electric field with relativity applied, i.e. an electric field viewed from the wrong reference frame. In reality, a magnetic field is a fundamental field which can exist in a certain reference frame without needing any help from an electric field. More generally, both electric fields and magnetic fields are part of one fundamental, unified entity: the electromagnetic field.

@aabhasdhaubanja1184 7 жыл бұрын

so if the electron wasn't moving would it be affected by the magnetic field??

@chisomodimmegwa3479 7 жыл бұрын

in magnetism you only work with moving electrons

@chisomodimmegwa3479 7 жыл бұрын

rather moving charges

@aabhasdhaubanja1184 7 жыл бұрын

thx for the reply

@farajalyami2044 6 жыл бұрын

Yes sure that will completely affect the magnetic field. The magnetic field is produced by only moving charges if they don’t move there is no magnetic field.

@gowrishetty5030 2 жыл бұрын

No, if the electron wasn't moving it would not be affected by a magnetic field, this is because only moving charges produce a magnetic field around themselves and when this moving charge that has a magnetic field around it enters an external magnetic field it will experience a force eg if a flowing current inside a wire is moves into a magnetic field it will experience a mechanical force because the magnetic field pushes against the wire, however if a wire does not carry a current and is placed in an external magnetic field it will not experience a force. To answer you question ; Only charges that are moving will be affected by a magnetic field

@George4943 7 жыл бұрын

Perhaps it is a silly question, but... (I hope someone can hazard an actual answer) . . . Why are the iron filings in lines? ___ Why not the alternative of filings in the blank spaces too all pointing correctly? Are they real? Actual separate lines in space. Non-continuous . . . coming in countable units.

@PigletCNC 7 жыл бұрын

I thought about this as well, but I have no good answer but a hypothesis: It is my belief that the filings attract each other a bit because they aren't evenly spaced. Thus they get bundled up. I think that because some are closer to others they bundle up with each other but not in like one big lump because the magnetic forces decay rapidly over distance. Thus causes them to appear as lines. If the particles were spaced as such that all would have equal force in any direction they'd stay put and you wouldn't get to see lines.

@George4943 7 жыл бұрын

I found an explanation. www.scienceforums.net/topic/88197-magnetic-field-lines-and-iron-filings/ Not that I really understand it.

@PigletCNC 7 жыл бұрын

Great! Yeah so it seems every filing wants to be a magnet. Because of the tendency of magnets to orient with south poles against the north poles, this will form a chain and the field causes them to follow a line like that. Also, because everything wants to be as 'simple' (low energy) as can be the groups seek each other out. It's still pretty vague and I hope I made it a bit more clearer. I am still studying the subject myself so I might be wrong here.

@Mani-em2bo 2 жыл бұрын

2021 anyone??

@dr.sharanjitsingh3972 3 жыл бұрын

2021 anyone

@kaliasahu8830 6 жыл бұрын

Oops

@imbesrs 12 жыл бұрын

dont get it...

@bluebro7201 3 жыл бұрын

Same

@appa609 11 жыл бұрын

No, no. The field line represents the force that would act on a magnetic north monopole at any point in the field. A massive monopole would almost certainly not take that path.

@jihan_fox2362 Жыл бұрын

14 YEARS AGO 😞

@nokwandandlovu1391 6 жыл бұрын

SO MUCH TALKING ......MY GOSH UV CONFUSED ME MORE

@coolleonid 6 жыл бұрын

@droelieboelie3269 3 жыл бұрын

Thanks for your very enlightening videos! You are awesome! Just... How dare you say Tesla's name wrong! He would be called a god if he were in the bible!