Luyện nói tiếng Anh bằng Shadowing qua video: Let There Be Light: Maxwell's Equation EXPLAINED for BEGINNERS

It is my fundamental belief that there are many complicated physics concepts

that can be explained to someone with just a basic understanding of high school physics and mathematics.

And this video is my attempt at explaining Maxwell's equations, or at least one of them.

So, first of all, why am I making this video?

Well, last week I did a poll on Instagram asking you guys what video you wanted to see first.

A video on Maxwell's equations or a video about the structure of the atom?

Maxwell's equations won out, so here we are.

Thank you so much if you voted in the poll, and if you're not already following me on Instagram, then please head over there and follow me.

I post one minute long physics videos as well as just random stuff I'm doing throughout the day on my stories.

And follow me on Twitter if you want to hear the worst physics puns you've ever heard in your life.

Anyway, let's get into the video.

Maxwell's equations are a set of four equations that brilliantly describe electricity and magnetism.

Collectively, this is known as electromagnetism.

They are complicated and intricate, so probably deserve about 10 videos to be dedicated to them.

So, to do justice to Maxwell's equations, in this video I won't be focusing on all four of them.

I'll just be focusing on one of them this one.

So let's get straight into it What do these symbols even mean?

Well, like I've already said Maxwell's equations focus on electricity

and magnetism now B in this case represents the magnetic field that we're studying.

Why do we use the letter B to represent a magnetic field?

Yeah, don't even ask don't ask the downward pointing triangle and the dot next to it together represent something known as Divergence, so what is divergence?

Right, here we go.

Well, the divergence is often applied to something known as a vector field.

Okay, Parth, now you're just saying words.

What the hell is a vector field?

Guys, trust me, bear with me here, it will all make sense very shortly.

Now, to understand divergence properly, first we need to understand what a vector field actually is.

So, a vector field can be thought of as a region of space where we can assign a vector, or an arrow pointing in a certain direction, to every point in that region of space.

Like I said already, by the way, a vector is just an arrow with a particular size size and pointing in a particular direction.

This vector can be used to represent something in the vector field.

A classic example is a vector field showing the direction and speed of wind on a weather map.

A lot of us have seen these on TV for example

where the vectors assigned to every point in this region basically show us the direction and speed of wind.

So for example at this point the wind is blowing really hard to the east

and at this point the wind is blowing really softly to the south.

The larger the vector the higher the wind speed and the direction shows the direction of the wind.

So this overall is vector field.

It's basically a field of vectors.

The vectors represent something, in this case the speed of the wind.

Now guys, before I continue, if my explanation of a vector field is not clear enough, then let me know in the comments down below.

I've got a couple more examples coming for you guys that should hopefully clear it up, but also if there's anything in this video that isn't quite clear, then let me know in the comments down below as well.

And I'm gonna be cheeky here, if you're enjoying the video so far then please leave a thumbs up.

But let's get back to it.

Here's another example of a vector field.

Coming back to electromagnetism, a classic example of a vector field is the magnetic field around a bar magnet.

We've often seen these in high school, especially demonstrated with a bar magnet and iron filings.

The iron filings are easily magnetized and

so follow the magnetic field around the bar magnet

because the bar magnets magnetic field exerts a force on each one of these little iron filings, and the magnetic field lines that we draw basically show the direction of force on these iron filings.

So yes, a magnetic field can be represented as a vector field, where this time a vector in the vector field represents the direction

and size of the force experienced by a magnetic object placed in the magnetic field.

So, now that we know that a magnetic field around a magnetic object can be represented as a vector field, let's get back to looking at the divergence of a vector field and what that means.

Well, when we're trying to find the divergence of a vector field, essentially what we do is we choose a small region of space within

that field and we see how much that vector field either points into that region or out of that region.

Again, this is fairly confusing, so let's use an example to demonstrate.

Once again, let's put aside magnetic fields and let's consider another vector field.

This time I want you to close your eyes and imagine you're drawing yourself a relaxing bath, because obviously there's no better place to do physics.

No, but seriously, imagine that you're running yourself a bath in a bath

that has taps at one end and the drain at the other end.

Now this is fairly uncommon, I know that usually the drain is on the same side as the taps, but for demonstration purposes let's imagine that they're on opposite ends of the bathtub.

Now let's say that in this case you've forgotten to plug the drain

so you're doing a really bad job of drawing yourself a bath

because the water flows into the bathtub from the taps and flows right back out from the drain.

Now at this point you're obviously wasting water and damaging the environment, but it's okay because it's for the sake of physics and because it's only in your head.

Now let's say that we're looking at the bathtub from above.

We can represent the flow of water on the floor of the bathtub with a vector field.

We know that at the tap end of the bath, the water is flowing down onto the floor of the bath and then spreading outwards.

In the middle region of the bathtub, water is flowing away from the tap end and towards the drain end.

And at the drain end, all of the water is flowing into the drain and down the plug hole.

Now, of course, it's important to realize that this is only the net or overall flow of the water, because of course, some of the water will reflect of the size of the bath and be flowing in all different directions.

But overall the water is flowing away from the tap end and towards the drain end.

Now let's say that the vector field at any point is represented by the vector V.

V standing for velocity, unlike B standing for magnetic field apparently.

But of course, because the vectors are different at every point along the bathtub floor, sometimes they're large, sometimes they're short, sometimes they point towards the right,

sometimes towards the left, V obviously changes at every point.

Okay, so now that we have a vector field, which represents the velocity of the water on the bathtub floor, let's take the divergence of the vector field.

Let's start then with the middle region of the bathtub floor.

When we're taking the divergence, we look at the vector field flowing into that circle and out of that circle.

In this case, water is flowing into the circle from the left and is flowing straight out to the right.

In other words, if we take the divergence of V in this region, then we say that its divergence is zero.

Because, and here's the thing, This means that overall there's no flow into the circle or out of the circle.

But hang on, aren't all regions in the vector field like that, where water flows in and flows straight back out again the other side?

Nah fam, check this out.

Let's say we now take our divergence at the tap end of the bathtub floor.

Now if we place our circle here, then clearly water is flowing out in all directions.

So overall there is a net flow of water outwards from our divergence circle.

Now because water is all flowing outwards, that means that this is a source of the water.

And this is fairly common terminology.

If the vector field is overall flowing outwards from your region, then that region is known as a source of the vector field.

And, more importantly, this region is said to have a positive divergence.

In other words, the divergence of the vector field V in this region is positive.

Now, conversely, we can take our divergence at the other end of the bathtub floor, this time at the drain end.

And we can clearly see in this region that all of the water is flowing in towards our circle.

This kind of region, where overall the vector field is flowing into our region, is known as a sink.

And a sink of the vector field is said to have a negative divergence.

And so that is how the divergence of a vector field works in a relatively intuitive way.

Of course, there's a little bit more mathematical subtlety and intricacy to it, but that's not really important to us right now.

So let's go back to Maxwell's equation that talks about the divergence of the magnetic field.

Now this equation tells us that the divergence of the magnetic field is zero...

100

always.

101

Because it's not saying that in some specific regions the divergence of the magnetic field is zero.

102

No, it's saying that the divergence of any magnetic field of any magnetic object is always zero.

103

This is really important because it tells us a couple of things.

104

Firstly, it tells us that there are no individual sources or sinks of magnetic field.

105

Compare this with electric fields, by the way, which has sources and sinks.

106

Positive charges are sources because the electric field goes outwards from a positive charge, and negative charges are sinks because the electric field points inwards towards a negative charge.

107

This is not true for magnetic fields according to Maxwell's equation.

108

So let's check this is true for the simple case of a bar magnet.

109

Let's see if we can find any sources or sinks of the magnetic field on this diagram.

110

Is there any region that we can draw where overall the magnetic field is either flowing in or flowing out?

111

Well, let's start with this region, just a random region in the magnetic field.

112

Look, magnetic field flows in and then it flows straight back out again.

113

So the divergence in this region is zero.

114

But what about the poles of the magnet?

115

This looks fairly promising because if we draw a sphere around the north pole of the magnet, for example, then we can clearly see that magnetic field is only flowing out of the sphere.

116

There's nothing flowing back in.

117

It's a source, right?

118

Well, no, not really.

119

The only reason it looks like a source is because we haven't drawn the magnetic field lines inside of the bar magnet.

120

But when we do, it looks like this.

121

And there you go.

122

Magnetic field now flowing in and flowing straight back out again.

123

From this, we can deduce something really important.

124

Maxwell's equation is telling us that there's no such thing as a magnetic monopole, or single individual pole.

125

You can't just have a North Pole by itself which gives out a magnetic field, and you can't just have a South Pole by itself either.

126

Whenever you have a magnetic substance, that substance will always have a North and a South Pole.

127

This is why when you chop a bar magnet in half, you don't just get a separate North Pole and a South Pole.

128

You now get two little bar magnets, each of which has a North Pole and a South Pole of its own.

129

However, interestingly, there are some modern theories that predict the existence of magnetic monopoles.

130

So, scientists have been on the search for the existence of these monopoles for a little while now.

131

No evidence has been found as of now, as of when I'm recording this video.

132

There's even an episode of the Big Bang Theory, where Sheldon develops a theory that predicts the existence of magnetic monopoles.

133

To search for evidence of this, the guys go on an expedition, I think to the Antarctic, and, spoiler alert, in the next episode they come back supposedly successful.

134

They think they found evidence for the magnetic monopole.

135

And this is a huge deal, because it means that Maxwell's equation is wrong.

136

And therefore, this evidence has started a new era in physics.

137

So, getting back to Maxwell's equations, you see what I mean about them being really complicated and intricate.

138

This video has gone on long enough and I've only discussed one of the four equations.

139

The equation that we discussed was probably one of the simpler ones to explain

140

and it's taken me this long ass video to do it.

141

So if you liked this video and found it useful, then please leave a thumbs up.

142

I really do appreciate it.

143

But now it's time for the weekly question of the week.

144

My weekly question of the week for you this week is what is your favorite thing about physics?

145

It can be a particular area of physics or it can be anything about physics as well.

146

Like the fact that it's evidence-based and it's probably the best thing

147

that we have in trying to understand how our universe works.

148

Also, comment down below if you want me to do another video covering another one of Maxwell's equations.

149

And yeah, if there's something that I haven't made quite clear enough, then let me know down below, and if I've made a mistake, then feel free to blast me down in the comments as well.

150

Subscribe if you haven't already for more physics content.

151

I make fun physics videos, though I don't have to try too hard because physics is already fun.

152

And hit that bell button to be notified every time I upload.

153

Okay, now that all the YouTube-y stuff is out the way, guys, thank you so much for watching.

154

I really appreciate it, and I will see you next time.

155

Buh-buh-buh-bye!

📺 Cùng kênh

LET THERE BE... Voltage? | Maxwell's Equation #2 Explained for Beginners

University StudentsBusiness English+1

Einstein Didn't Invent Relativity! - Physics Explained for Beginners

University StudentsDaily Conversation

✨ Video gợi ý

198 câu

The Only Video on Maxwell’s Equations You’ll Ever Need

IELTS PrepTOEFL Prep+2

204 câu

Polarization of light, linear and circular | Light waves | Physics | Khan Academy

IELTS PrepTOEFL Prep+2

73 câu

Phương Pháp Shadowing Là Gì?

Shadowing là kỹ thuật học ngôn ngữ có cơ sở khoa học, ban đầu được phát triển cho chương trình đào tạo phiên dịch viên chuyên nghiệp và được phổ biến rộng rãi bởi nhà đa ngôn ngữ học Dr. Alexander Arguelles. Nguyên lý cốt lõi đơn giản nhưng cực kỳ hiệu quả: bạn nghe tiếng Anh của người bản xứ và lặp lại to ngay lập tức — như một "cái bóng" (shadow) đuổi theo người nói với độ trễ chỉ 1–2 giây. Khác với luyện ngữ pháp hay học từ vựng bị động, Shadowing buộc não bộ và cơ miệng phải đồng thời xử lý và tái tạo ngôn ngữ thực tế. Các nghiên cứu khoa học xác nhận phương pháp này cải thiện đáng kể phát âm, ngữ điệu, nhịp điệu, nối âm, kỹ năng nghe và độ lưu loát khi nói — đặc biệt hiệu quả cho người luyện IELTS Speaking và muốn giao tiếp tiếng Anh tự nhiên như người bản ngữ.

Phương pháp shadowing: đọc hướng dẫn từng bước đầy đủ →

Luyện nói tiếng Anh bằng Shadowing qua video: Let There Be Light: Maxwell's Equation EXPLAINED for BEGINNERS

LET THERE BE... Voltage? | Maxwell's Equation #2 Explained for Beginners

Einstein Didn't Invent Relativity! - Physics Explained for Beginners

The Only Video on Maxwell’s Equations You’ll Ever Need

Polarization of light, linear and circular | Light waves | Physics | Khan Academy

Superfluid Dark Matter

What science can’t answer, according to physicist Jim Al-Khalili | Big Think

If You Don't Understand Quantum Physics, Try This!

Euler's Formula Poem

How real are the real numbers, really?

The Professor Who Taught People How To Think (1962)

Man of the future | Nikola Tesla | edit

The Goofiest Space Experiment In History

Black Holes Explained – From Birth to Death

Mục Tiêu Nói Chuyện Cho Đoạn Video Này

Tổng Hợp Cụm Từ

Cải Thiện Những Điểm Yếu Của Bạn

Phương Pháp Shadowing Là Gì?