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
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.
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.
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).
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.
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??
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.
@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.
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?
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?
"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?
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
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 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.
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.
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.
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.
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!
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.
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
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.
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.
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!
It did seem to disappear. Don't know how that happened. I now added it back to the physics playlist right before this video.
Crazy to think people 10 years ago were cramming exactly how i am a decade later. Makes you wonder where everyone is now.
Bro i am 14
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
2020 anyone?
yep
I m
Physics 2 exam coming up
2021, actually.
Fs
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.
Thanks for existing 🙌🏼🙏🏼🙏🏼
these videos are still saving students
Yep 👍
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.
holy crap the transcribed audio (CC) thingy actually works for his videos!
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).
Bro commented this in 2011 smth man .. hey how are u rn ( just wanted to talk to someone with old comments like this )
it doesn't have to be perpendicular for the cross product to make sense, just need to not be parallel
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.
Times n(unit vector perpendicular to the plane of a and b) of course so you get a vector back.
Rockyzach88, Richard S is right, this formular he is using is used in centripetal force
this dude studers so much
This says it includes the right hand rule, but there is no mention of it
Your diagram of the field lines is way elongated. Your compass needle needle wasn't even close to the north lol.
so force is newtons, charge is coulombs, velocity is meters per second and this is the fffffb-units
Everything Falls in 9.8 meters per to the 2nd
Actually magnetic field si unit is tesla
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??
Why there is no more a video? :( Is there anything like a CD/DVD of Khan videos?
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.
Magnetic force does not move
on ya SAL! your the reason i am sort of scraping by year 12 Physics!
I am really curious where did life take you after 9 years
@@karman103batth4 Same here
@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.
thank you so much
i was 10years old when this video is uploaded
If the atoms are all in alignment and spinning; could the magnetic force be a result of the centrifical force of the spinning atoms?
I was born when this video uploaded
You're 11 why are you watching this
I was 2 when it was lol im 14 now
@@abhirupsaha2803 why shouldn't be if he is interested in science he will
i was four
not that anyone cares...
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?
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?
2021 anyone? If yes don't just see comments 😂 focus.
"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?
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
This is more Interesting 😅😆 it
Oh what would I do w/o Khan?
haha me toooo!!
Thank u this video helps me so much
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.
You have any articles that confirm what you are saying?
@@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.
nice lecture
One person belives that science does not exits
That is a fool
2023
The fact that this was 13yrs ago😳
How do I find the magnitude
I hope you answer my questions what is the proton charge in magnesium posatefe charge is it protons wev
Omg the only thing that surprised me that this video is about 10 years ago .. Woow o,o
i think the unit for B is teslas...
watching in 2024 ? 🤍
Interesting
Amazing
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.
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.
I found an explanation. www.scienceforums.net/topic/88197-magnetic-field-lines-and-iron-filings/
Not that I really understand it.
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.
2021
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!
Tesla...a deserving fellow...hahaha yeah to say the least
a deserving? more like an absolute genius!
Yo!!!! My fave thq
What confuddled me for the longest time is I thought he was writing beta instead of just B and referring to something entirely else
The ghost of Khanacademy did it.
But why f = QvB
have you ever thing there is more than 3 dimension ?
Fix your question so it can be answered
I'm 8 years late but yeah, I think there are more than 3 dimensions. We just can't comprehend it.
so if the electron wasn't moving would it be affected by the magnetic field??
in magnetism you only work with moving electrons
rather moving charges
thx for the reply
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.
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
Please make your videos in hindi
@villebacker LOL
5 star youtube video. Truly.
Hi
Are you alive sir?
couldn't the units be written as kg/Cs?
Subtitles --> 4:37
what does it say? i think they changed the subs after so many years.
Thanks
NIKOLA tesla, not Nikolai! good vid tho
the 2 ppl who disliked this are physics teaches who are not as smart as this guy
Nikola Tesla- theres not "i" at the end, sal :)
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.
@GenericCoder
add
youtube
and remove the spaces
@ajskilton it does not really matter. it's just a math trick.
LATE NIGHT CRAMMING
14 YEARS AGO 😞
What is B
B units are Teslas
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.
Any one in 2021 😊
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!
magnetic field.. i think
2021 anyone??
dont get it...
Same
I'm from 2021 (a future guy) 😂
SO MUCH TALKING ......MY GOSH UV CONFUSED ME MORE
2021 anyone
"two non perpendicular vectors" my bad
i had it before i got here
in germany monopoles were created
Physics exam in 5 hrs😑
2021😍😍
2022 anyone?
Your carrying my generation
Oops
Soo confused 🤷♂️🤷♀️😂🤦♀️🤦♂️
k
Bro this is 15 yrs old😂💀
this guy talks a lot doesn't he?
no
NOOOOOOOOOOO! More magents!
more spelling
And the 💯 th coment is
Bɪɴᴏᴅ!
Actually 101 xD
This video is 13 years old ...smh
Good video but this guy talks too much, and unnecessary things. smh
bad drawing
2022 anyone?