## Rabu, 25 Agustus 2010

### Fisika untuk Universitas

Fisika untuk Universitas

Ditujukan untuk meningkatkan kualitas proses dan hasil perkuliahan Fisika di tingkat Universitas

Kelistrikan dan Kemagnetan

Topics covered:

Electric Field
Field Lines
Superposition
Inductive Charging
Dipoles
Induced Dipoles

Instructor/speaker: Prof. Walter Lewin

### Video

Today I'm going to work with you on a new concept and that is the concept of what we call electric field.

We spend the whole lecture on electric fields.

If I have a -- a charge, I just choose Q, capital Q and plus at a particular location and at another location I have another charge little Q, I think of that as my test charge.

And there is a separation between the two which is R.

The unit vector from capital Q to li- little Q is this vector.

And so now I know that the two charges if they were positive -- let's suppose that little Q is positive, they would repel each other.

Little Q is negative they would attract each other.

And let this force be F and last time we introduced Coulomb's law that force equals little Q times capital Q times Coulomb's constant divided by R squared in the direction of R roof.

The two have the same sign.

It's in this direction.

If they have opposite sign it's in the other direction.

And now I introduce the idea of electric field for which we write the symbol capital E.

And capital E at that location P where I have my test charge little Q, at that location P is simply the force that a test charge experienced divided by that test charge.

So I eliminate the test charge.

So I get something that looks quite similar but it doesn't have the little Q in it anymore.

And it is also a vector.

And by convention, we choose the force such that if this is a positive test charge then we say the E field is away from Q if Q is positive, if Q is negative the force is in the other direction, and therefore E is in the other direction.

So we adopt the convention that the E field is always in the direction that the force is on a positive test charge.

What you have gained now is that you have taken out the little Q.

In other words, the force here depends on little Q.

Electric field does not.

The electric field is a representation for what happens around the charge plus Q.

This could be a very complicated charge configuration.

An electric field tells you something about that charge configuration.

The unit for electric field you can see is newtons divided by coulombs.

In SI units and normally we won't even indicate the-- the unit, we just leave that as it is.

Now we have graphical representations for the electric field.

Electric field is a vector.

So you expect arrows and I have here an example of a -- a charge plus three.

So by convention the arrows are pointing away from the charge in the same direction that a positive test charge would experience the force.

And you notice that very close to the charge the arrows are larger than farther away.

That it, that sort of represents- is trying to represent- the inverse R square relationship.

Of course it cannot be very qualitative.

But the basic idea is this is of course spherically symmetric, if this is a point charge.

The basic idea is here you see the field vectors and the direction of the arrow tells you in which direction the force would be, if it is a positive test charge.

And the length of the vector give you an idea of the magnitude.

And here I have another charge minus one.

Doesn't matter whether it is minus one coulomb or minus microcoulomb.

Just it's a relative representation.

And you see now that the E field vectors are reversed in direction.

They're pointing towards the minus charge by convention.

And when you go further out they are smaller and you have to go all the way to infinity of course for the field to become zero.

Because the one over R square field falls off and you have to be infinitely far away for you to not experience at least in principle any effect from the..

from the charge.

What do we do now when we have more than one charge?

Well, if we have several charges -- here we have Q one, and here we have Q two, and here we have Q three, and let's say here we have Q of i, we have i charges.

And now we want to know what is the electric field at point P.

So it's independent of the test charge that I put here.

You can think of it if you want to as the the force per unit charge.

You've divided out the charge.

So now I can say what is the E field due to Q one alone?

Well, that would be if Q one were positive then this might be a representation for E one.

If Q two were negative, this might be a representation for E two, pointing towards the negative charge.

And if this one were negative, then I would have here a contribution E three, and so on.

And now we use the superposition principle as we did last time with Coulomb's law, that the net electric field at point P as a vector is E one in reference of charge Q one, plus the vector E two, plus E three, and so on and if you have i charges, it is the sum of all i charges of the individual E vectors.

Is it obvious that the superposition principle works?

No.

Does it work?

Yes.

How do we know it works?

Because it's consistent with all our experimental results.

So we take the superposition principle for granted and that is acceptable.

But it's not obvious.

If you tell me what the electric field at this point is, which is the vectorial sum of the individual E field vectors, then I can always tell you what the force will be if I bring a charge at that location.

I take any charge that I always would carry in my pocket, I take it out of my pocket and I put it at that location.

And the charge that I have in my pocket is little Q.

Then the force on that charge is always Q times E.

Doesn't matter whether Q is positive, then it will be in the same direction as E.

If it is negative it will be in the opposite direction as E.

If Q is large the force will be large.

If Q is small the force will be small.

So once you know the E field it could be the result of very complicated charge configurations.

The real secret behind the concept of an E field is that you bring any charge at that location and you know what force acts at that point on that charge.

If we try to be a little bit more quantitative, suppose I had here a charge plus three and here I had a charge minus one.

Here's minus one.

And I want to know what the field configuration is as a result of these two charges.

So you can go to any particular point.

You get an E vector which is going away from the plus three, you get one that goes to minus one, and you have to vectorially add the two.

If you are very close to minus one, it's very clear because of the inverse R square relationship that the minus one is probably going to win.

Let's in our mind take a plus test charge now.

And we put a plus test charge very close to minus one, say put it here, even though plus three is trying to push it out, clearly minus one is most likely to win.

And so there will probably be a force on my test charge in this direction.

The net result of the effects of the two.

Suppose I take the same positive test charge and I put it here, very far away, much farther away than this separation.

What do you think now is the direction of the force on my plus charge?

Very far away.

Excuse me.

Why do you think it's to the left?

Do you think minus one wins?

A: [inaudible].

Do you really think the minus one is stronger than the plus three because the plus three will push it out and the minus one tries to lure it in, right, if the test charge is positive.

A: [inaudible] plus two.

So if you're far away from a configuration like this, even if you were here, or if you were there, or if you're way there, clearly the field is like a plus two charge.

And falls off as one over R squared.

So therefore, if you're far away the force is in this direction.

And now look, what is very interesting.

Here if you're close to the minus one, the force is in this direction.

Here when you're very far away, maybe I should be all the way here, it's in that direction.

So that means there must be somewhere here the point where the E field is zero.

Because if the force is here in this direction but ultimately turns over in that direction, there must be somewhere a point where E is zero.

And that is part of your assignment.

I want you to find that point for a particular charge configuration.

So let's now go to-- some graphical representations of a situation which is actually plus three minus one.

Try to improve on the light situation.

And let's see how these electric vectors, how they show up in the vicinity of these two charges.

So here you see the plus three and the minus one, relative units, and let's take a look at this in some detail.

First of all the length of the arrows again indicates the strength.

It gives you a feeling for the strength.

It's not very quantitative of course.

And so let's first look at the plus three, which is very powerful.

You see that these arrows all go away from the plus three and when you're closer to the plus three, they're stronger, which is a representation of the inverse R square field.

If you're very close to the minus one, ah the arrows are pointing in towards the minus one, because the one over R square, the minus one wins.

And so you see they're clearly going into the direction of the minus one.

Well, if you're in between the plus and the minus on this line, always the E field will be pointing from the plus to the minus.

Because the plus is pushing out and the minus is sucking in.

So the two support each other.

But now if you go very far away from this charge configuration, anywhere but very far away, much farther than the distance between the two charges, so somewhere here, or somewhere there, or somewhere there, or here, notice that always the arrows are pointing away.

And the reason is that plus three and minus one is as good as a plus two if you're very very far away.

But of course when you're very close in, then the field configuration can be very, very complicated.

But you see very clearly that these arrows are all pointing outwards.

None of them come back to the minus one.

None of them point to the minus one direction.

And that's because the plus three is more powerful and then there is here this point and only one point whereby the electric field is zero.

If you put a positive test charge here, the minus will attract it, the plus will repel it, and therefore there comes a point where the two cancel each other exactly.

Now there is another way of electric field representation which is more organized.

And we call these field lines.

So you see again the plus three and you see there the minus one.

If I release right here or I place here a positive test charge, all I know is that the force will be tangential to the field lines.

That is the meaning of these lines.

So if I'm here, the force will be in this direction.

If I put a positive test charge here, the force will be in this direction, and of course, if it's a negative charge the force flips over.

So the meaning of the field lines are that it always tells you in which direction a charge experiences a force.

A force a positive charge always in the direction of the arrows, tangentially to the field lines and a negative charge in the opposite direction.

How many field lines are there in space?

Well of course there are an infinite number.

Just like these little arrows that we had before, we only sprinkled in a few but of course in every single point there is an electric field and so you can put in an infinite number of field lines and that would make this a representation of course useless.

So we always limit ourselves to a certain number.

If you look very close to the minus one, notice that all the field lines come in on the minus one.

We understand that of course because a positive charge would want to go to the minus one.

If you're very close to the plus and they all go away from the plus because they're being repelled...

You can sort of think as these field lines if you want to imagine the configuration that the plus charges blow out air like a hairdryer, and that the minus suck in air like a vacuum cleaner, and then you get a feeling for there is on this left side here this hairdryer which wants to blow out stuff and then there is that little sucker that wants to suck something in and it succeeds to some degree, it's not as powerful as the plus three, though.

Have we lost all information about field strength?

We had earlier with these arrows, we had the length of the arrow, the magnitude of the field was represented.

Yeah, you have lost that, but there is still some information on field strength.

If the lines are closer together, if the density of the lines is high, the electric field is stronger than when the density becomes low.

So if you look for instance here, look how many lines there are per few millimeters, and when you go further out these lines spread out, that tells you the E field is going down, the strength of the E field is going down.

It's the one over R square field of course.

If you want to make these drawings what you could do to make them look good, you can make three times more field lines going out from the plus in this case than return to the minus one.

So the field lines are very powerful and we will often think in terms of electric fields and the line configurations and you will have several homework problems that deal with electric fields and with the electric field lines.

If an electric field line is straight, so I have electric fields, get some red chalk, say we have fields that are like this, straight E field lines, and I release a charge there, for instance a positive charge, then the positive charge would experience a force exactly in the same direction as the field lines, because the tangential now is in the direction of the field line, it would become accelerated in this direction and would always stay on the field lines.

If I release it with zero speed, start to accelerate and it would stay on the field lines.

In a similar way, if we think of the earth as having a gravitational field, with eight o one we may never have used that word, gravitational field, but in physics we think of the -- of gravity of also being a field.

If I have here a piece of chalk the-- the field lines, the gravitational field lines, here in twenty-six one hundred, nicely parallel and straight and if I release this piece of chalk at zero speed it will begin to move in the direction of the field lines, and it will stay on the field lines.

So now you can ask yourself the question if I release a charge would it always follow the field lines?

And the answer is no.

Only in this very special case.

Pengembangan Perkuliahan

1. Buatlah sebuah Esai mengenai materi perkuliahan ini

2. Buatlah sebuah kelompok berjumlah 5 orang untuk menganalisis materi perkuliahan ini

3. Lakukan Penelitian Sederhana dengan kelompok tersebut

4. Hasilkan sebuah produk yang dapat digunakan oleh masyarakat

5. Kembangkan produk tersebut dengan senantiasa meningkatkan kualitasnya

Ucapan Terima Kasih Kepada:

1. Para Dosen MIT di Departemen Fisika

a. Prof. Walter Lewin, Ph.D.

b. Prof. Bernd Surrow, Ph.D.

#### Staff

Visualizations:
Prof. John Belcher

Instructors:
Dr. Peter Dourmashkin
Prof. Bruce Knuteson
Prof. Gunther Roland
Prof. Bolek Wyslouch
Dr. Brian Wecht
Prof. Eric Katsavounidis
Prof. Robert Simcoe
Prof. Joseph Formaggio

Dr. Peter Dourmashkin
Prof. Robert Redwine

Technical Instructors:
Andy Neely
Matthew Strafuss

Course Material:
Dr. Peter Dourmashkin
Prof. Eric Hudson
Dr. Sen-Ben Liao

#### Acknowledgements

The TEAL project is supported by The Alex and Brit d'Arbeloff Fund for Excellence in MIT Education, MIT iCampus, the Davis Educational Foundation, the National Science Foundation, the Class of 1960 Endowment for Innovation in Education, the Class of 1951 Fund for Excellence in Education, the Class of 1955 Fund for Excellence in Teaching, and the Helena Foundation. Many people have contributed to the development of the course materials. (PDF)

2. Para Dosen Pendidikan Fisika, FPMIPA, Universitas Pendidikan Indonesia.

Terima Kasih Semoga Bermanfaat dan mohon Maaf apabila ada kesalahan.

## Rabu, 18 Agustus 2010

### Jaringan Pendidikan IPTEK Nuklir Indonesia

Nuclear Education Online

Pusat Pengembangan Pendidikan IPTEK Nuklir

The sun is basically a giant ball of hydrogen gas undergoing fusion
into helium gas and giving off vast amounts of energy in the process.
Source: NASA (Public Domain)

## Types of Nuclear Reactors

Diagram of a Boiling Water Nuclear Reactor

Source: U.S. Nuclear Regulatory Commission (Public Domain)

Diagram of a Pressurized Nuclear Reactor System

Source: U.S. Nuclear Regulatory Commission (Public Domain)

Nuclear reactors are large machines that contain and control nuclear chain reactions, while releasing heat at a controlled rate.

A nuclear power plant uses the heat supplied by the nuclear reactor to turn water into steam, which drives turbine-generators that generate electricity.

### There Are Two Types of U.S. Reactors

Just as there are different approaches to designing and building airplanes and automobiles, engineers have developed different types of nuclear power plants. Two types are used in the United States: boiling-water reactors and pressurized-water reactors.

#### Boiling-Water Reactors

In a boiling-water reactor, the water heated by the reactor core turns directly into steam in the reactor vessel and is then used to power the turbine-generator.

#### Pressurized-Water Reactors

In a pressurized-water reactor, the water heated by the reactor core is kept under pressure so that it does not turn to steam at all — it remains liquid. This hot radioactive water flows through a piece of equipment called a steam generator.

A steam generator is a giant cylinder with thousands of tubes in it that the hot radioactive water can flow through and heat up. Outside these hot tubes in the steam generator is nonradioactive water (or clean water), which eventually boils and turns to steam .

The radioactive water flows back to the reactor core, where it is reheated and then sent back to the steam generator. The clean water may come from one of several sources including oceans, lakes, or rivers.

Source:
http://www.eia.gov/kids/energy.cfm

### Fisika untuk Universitas

Fisika untuk Universitas

Ditujukan untuk meningkatkan kualitas proses dan hasil perkuliahan Fisika di tingkat Universitas

# 3: Vectors

The bad news today is that there will be quite a bit of math.

But the good news is that we will only do it once and it will only take something like half-hour.

There are quantities in physics which are determined uniquely by one number.

Mass is one of them.

Temperature is one of them.

Speed is one of them.

We call those scalars.

There are others where you need more than one number for instance, on a one- dimensional motion, velocity it has a certain magnitude--

that's the speed--

but you also have to know whether it goes this way or that way.

So there has to be a direction.

Velocity is a vector and acceleration is a vector and today we're going to learn how to work with these vectors.

A vector has a length and a vector has a direction and that's why we actually represent it by an arrow.

We all have seen...

this is a vector.

Remember this--

this is a vector.

Ucapan Terima Kasih Kepada:

1. Para Dosen MIT di Departemen Fisika

a. Prof. Walter Lewin, Ph.D.

b. Prof. Bernd Surrow, Ph.D.

2. Para Dosen Pendidikan Fisika, FPMIPA, Universitas Pendidikan Indonesia.

Terima Kasih Semoga Bermanfaat dan mohon Maaf apabila ada kesalahan.

## Selasa, 17 Agustus 2010

### Fisika Untuk Universitas

Fisika untuk Universitas

Ditujukan untuk meningkatkan kualitas proses dan hasil perkuliahan Fisika di tingkat Universitas

# 2: Introduction to Kinematics

We will discuss velocities and acceleration.

I have a motion of an object along a straight line--

we'll call that one-dimensional motion.

And I'll tell you that the object is here at time t1.

At time t2, it's here.

At time t3, it's there.

At time t4, it's here and at time t5, it's back where it was at t1.

And here you see the positions in x where it is located at that moment in time.

I will define this to be the increasing value of x.

It's my free choice, but I've chosen this now.

Now we will introduce what we call the average velocity.

I put a bar over it.

That stands for average between time t1 and time t2.

That we define in physics as x at time t2 minus x at time t1 divided by t2 minus t1.

That is our definition.

In our case, because of the way that I define the increasing value of x, this is larger than 0.

However, if I take the average velocity between t1 and t5 that would be 0, because they are at the same position so the upstairs is 0.

If I had chosen t4 and t2--

average velocity between time t2 and t4--

you would have seen that that is negative because the upstairs is negative.

Notice that I haven't told you where I choose my zero on my x axis.

It's completely unimportant for the average velocity.

It makes no difference.

However, if I had chosen this to be the direction of increasing x then, of course, the signs would flip.

Then this would have been negative and this would have been positive.

So the direction, that you are free to choose determines the signs.

The location where you put your zero is not important but signs in physics do matter.

Signs are important.

Whether you owe me money or I owe you money the difference is only a minus sign but I think it's important for you.

Now I will give you not only the positions--

as I did here on the x axis at discrete moments in time--

but I'm going to tell you exactly where the object is at any moment in time.

Here you see an xt diagram so you see that at t1, the object is at position xt1.

This is the road of the object.

This is the straight line, where it's moving.

It starts here and it goes to this position.

It goes to this one, it comes back to t4 and it comes back here.

I will tell you now every moment in time in between.

And there it goes.

Voila.

This is now information that is way more.

You have the information at any moment in time.

Notice that I now did choose x = 0.

I chose it somewhere here but I could have chosen it at any other point--

for whatever follows you will see that it makes no difference--

so I have chosen a zero point so that I can make a graph.

And now we will look at the average velocity in a somewhat different way.

Say I choose my time t2 and t3.

I draw here now this line.

And this angle I call alpha and this part here I call delta x and this here is delta t.

And so you could right now--

if you're careful about your sign convention--

you could write down now that the average velocity equals delta x divided by delta t.

But be careful.

Ucapan Terima Kasih Kepada:

1. Para Dosen MIT di Departemen Fisika

a. Prof. Walter Lewin, Ph.D.

b. Prof. Bernd Surrow, Ph.D.

2. Para Dosen Pendidikan Fisika, FPMIPA, Universitas Pendidikan Indonesia.

Terima Kasih Semoga Bermanfaat dan mohon Maaf apabila ada kesalahan.

## Selasa, 10 Agustus 2010

### Fisika untuk Universitas

Fisika untuk Universitas

Ditujukan untuk meningkatkan kualitas proses dan hasil perkuliahan Fisika di tingkat Universitas

Kelistrikan dan Kemagnetan

Topics covered:

What holds our world together?
Electric Charges (Historical)
Polarization
Electric Force
Coulomb's Law

Instructor/speaker: Prof. Walter Lewin

# Syllabus

## Course Meeting Times

Lectures: 3 sessions / week, 1 hour / session
Recitations: 2 sessions / week, 1 hour / session

## Course Description

In addition to the basic concepts of Electromagnetism, a vast variety of interesting topics are covered in this course: Lightning, Pacemakers, Electric Shock Treatment, Electrocardiograms, Metal Detectors, Musical Instruments, Magnetic Levitation, Bullet Trains, Electric Motors, Radios, TV, Car Coils, Superconductivity, Aurora Borealis, Rainbows, Radio Telescopes, Interferometers, Particle Accelerators (a.k.a. Atom Smashers or Colliders), Mass Spectrometers, Red Sunsets, Blue Skies, Haloes around Sun and Moon, Color Perception, Doppler Effect, Big-Bang Cosmology.

There is a build-your-own-motor contest as part of this course (see Calendar).

## Textbook

Giancoli, D. C. Physics for Scientists & Engineers. Vol. 2. Prentice Hall.

------. The Study Guide and Student Solutions Manual. 3rd ed. Prentice Hall.

## Lectures - Homework - Solutions - Exams - Quizzes - Grades

There will be 36 lectures, 10 problem sets, 3 exams during regular lecture hours, and a 3-hour final. Weekly 15-minute quizzes will be given in recitations. During exams, I expect you to know all material covered in (i) the lectures, (ii) the reading assignments, (iii) the problem sets and (iv) recitations. When the need arises, Lecture Supplements (see Lecture Notes) will be made available.

Please hand in your homework on the due dates before 4 PM. Three problems, randomly chosen, will be graded. Solutions will be made available on the day after the due dates.

The homework counts for 10%, the weekly quizzes for 15%, each exam for 15%, and the final exam counts for 30% of your course grade.

There will be no make-up exams!

A missed homework, quiz or exam counts as a zero. Only in case of verifiable illness can you be excused from taking one of the 3 exams. If at all possible, this should be done before the exam.

## Recitations

There are 28 recitation sections. If for any reason you want to change section, please see the Course Manager; she will accommodate you as much as possible.

I'm Walter Lewin.

My lectures will in general not be a repeat of your book but they will be complementary to the book.

The book will support my lectures.

My lectures will support the book.

You will not see any tedious derivations in my lectures.

For that we have the book.

But I will stress the concepts and I will make you see beyond the equations, beyond the concepts.

I will show you whether you like it or not that physics is beautiful.

And you may even start to like it.

I suggest you do not slip up, not even one day, eight o two is not easy.

We have new concepts every week and before you know you may be too far behind.

Electricity and magnetism is all around us.

We have electric lights, Electric clocks.

We have microphones, calculators, televisions, VCRs, radio, computers.

Light itself is an electromagnetic phenomenon as radio waves are.

The colors of the rainbow in the blue sky are there because of electricity.

And I will teach you about that in this course.

Cars, planes, trains can only run because of electricity.

Horses need electricity because muscle contractions require electricity.

Your nerve system is driven by electricity.

Atoms, molecule, all chemical reactions exist because of electricity.

You could not see without electricity.

Your heart would not beat without electricity.

And you could not even think without electricity, though I realize that even with electricity some of you may have a problem with that.

The modern picture of an atom is a nucleus, which is very small compared to the size of the atom.

The nucleus has protons, which are positively charged and it has neutrons, which have no charge.

The mass of the proton is approximately the same as the mass of the neutron.

It's about six point seven times ten to the minus twenty-seventh kilograms.

One point seven.

The positive charges here with the nucleons, with the neutrons, and then we have electrons in a cloud around it.

And if the atom is neutral, the number of electrons and the number of protons is the same.

If you take one electron off you get a positive ion.

If you add an electron then you get a negative ion.

The charge of the electron is the same as the charge of the proton.

That's why the number is the same for neutral atoms.

The mass of the electron is about eighteen hundred thirty times smaller than the mass of the proton.

It's therefore negligibly small in most cases.

All the mass of an atom is in the nucleus.

If I take six billion atoms lined up touching other, I take six billion because that's about about the number of people on earth.

Then you would only have a length of sixty centimeters.

Gives you an idea of how small the atoms are.

The nucleus has a size of about ten to the minus twelve centimeters.

And the atom itself is about ten thousand times larger.

The cloud of electrons, which is about ten to the minus eight centimeters.

And if you line six billion of those up you only get this much.

Already in six hundred BC, it was known that if you rub amber that it can attract pieces of dry leaves.

And the Greek word for amber is electron.

So that's where electricity got its name from.

In the sev- sixteenth century there were more substances known to do this.

For instance glass and sulfur.

And it was also known and written that when people were bored at parties that the women would rub their amber jewelry and would touch frogs, which then would start jumping of desperation, which people considered to be fun, not understanding what actually was happening to the amber nor what was happening to the frogs.

In the eighteenth century it was discovered that there are two types of electricity.

One if you rub glass and another if you rub rubber or amber for that matter.

Let's call one A and the other B.

It was known that A repels A and B repels B but A attracts B.

And it was Benjamin Franklin without any knowledge of electrons and protons who introduced the idea that all substances are penetrated with what he called electric fluid, electric fire.

And he stated if you get too much of the fire then you're positively charged and if you have a deficiency of that fire, then you're negatively charged.

He introduced the sign convention and he decided that if you rub glass that that is an excess of fire and he called that therefore positive.

You will see later in this course why this choice he had fifty percent chance is extremely unfortunate but we have to live with it.

So if you take this fluid according to Benjamin Franklin and bring it from one substance to the other, then the one that gets an excess becomes positively charged but automatically as a consequence of that the one from which you take the fluid becomes negatively charged.

And so that's the whole idea behind the conservation of charge.

You cannot create charge.

If you create plus then you automatically create minus.

Plus and plus repel each other.

Minus and minus repel each other.

And plus and minus attract.

And Benjamin Franklin who did experiments also noticed that the more fire you have the stronger the forces.

The closer these objects are to each other, the stronger the forces.

And there are some substances that he noticed, which conduct this fluid, which conduct this fire, and they are called conductors.

If I have a glass rod as I have here and I rub it then it gets this positive charge that we just discussed.

So here is this rod and I rub it with some silk and it will get positively charged.

What happens now to an object that I bring close to this rod and I will start off with taking a conductor.

And the reason why I choose a conductor is that conductors have a small fraction of their electrons, which are not bound to atoms but which can freely move around in the conductor.

That's characteristic for a conductor, for metals.

That's not the case with nonconductors.

There the all electrons are fixed to individual atoms.

So here we have a certain fraction of electrons that can wander around.

What's going to happen that electrons want to be attracted by these positive charges.

Plus and minus attract each other.

And so some of these electrons, which can freely move will move in this direction and so the plus stay behind.

This process we call induction.

You get sort of a polarization.

You get a charge division.

It's a very small effect, perhaps only one in ten to the thirteen electrons that was originally here will end up here but that's all it takes.

So we get a polarization and we get a little bit more negative charge on the right side than we have on the left side.

And so what's going to happen is, since the attraction between these two will be stronger than the repelling force between these two because the distance is smaller and Franklin had already noticed the shorter the distance the stronger the force.

What will happen is that if this object is free to move it will move towards this rod.

And this is the first thing that I would like you to see.

I have here a conductor that is a balloon, helium-filled balloon.

And I will rub this rod with silk.

And as I approach that balloon you will see that the balloon comes to the rod.

I will then try to rub with that rod several times on that balloon.

It will take a while perhaps because the rod itself is a very good nonconductor.

It's not so easy to get charge exchange between the two.

But if I do it long enough I can certainly make that balloon positive.

Then they're both positive.

And then they will repel each other.

But first, the induction part, whereby you will see the balloon come to the glass rod.

These experiments work best when it is dry, in the winter.

They don't work so well when it is humid so it's a good time to teach eight o two in the winter.

OK there we go this should be positively charged now.

And the balloon wants to come to the glass.

You see that?

Very clearly.

Pengembangan Perkuliahan

1. Buatlah sebuah Esai mengenai materi perkuliahan ini

2. Buatlah sebuah kelompok berjumlah 5 orang untuk menganalisis materi perkuliahan ini

3. Lakukan Penelitian Sederhana dengan kelompok tersebut

4. Hasilkan sebuah produk yang dapat digunakan oleh masyarakat

5. Kembangkan produk tersebut dengan senantiasa meningkatkan kualitasnya

Ucapan Terima Kasih Kepada:

1. Para Dosen MIT di Departemen Fisika

a. Prof. Walter Lewin, Ph.D.

b. Prof. Bernd Surrow, Ph.D.

#### Staff

Visualizations:
Prof. John Belcher

Instructors:
Dr. Peter Dourmashkin
Prof. Bruce Knuteson
Prof. Gunther Roland
Prof. Bolek Wyslouch
Dr. Brian Wecht
Prof. Eric Katsavounidis
Prof. Robert Simcoe
Prof. Joseph Formaggio

Dr. Peter Dourmashkin
Prof. Robert Redwine

Technical Instructors:
Andy Neely
Matthew Strafuss

Course Material:
Dr. Peter Dourmashkin
Prof. Eric Hudson
Dr. Sen-Ben Liao

#### Acknowledgements

The TEAL project is supported by The Alex and Brit d'Arbeloff Fund for Excellence in MIT Education, MIT iCampus, the Davis Educational Foundation, the National Science Foundation, the Class of 1960 Endowment for Innovation in Education, the Class of 1951 Fund for Excellence in Education, the Class of 1955 Fund for Excellence in Teaching, and the Helena Foundation. Many people have contributed to the development of the course materials. (PDF)

2. Para Dosen Pendidikan Fisika, FPMIPA, Universitas Pendidikan Indonesia.

Terima Kasih Semoga Bermanfaat dan mohon Maaf apabila ada kesalahan.

## Senin, 09 Agustus 2010

### PUSTAKA FISIKA (PF)

1. Sebuah Visi Pengumpulan 100.000 Buah Buku yang terkait dg Fisika
2. Pengumpulan Data-Data Kefisikaan sebesar 1 Terra byte

Tempat Pengumpulan dan Pendataan Buku-buku fisika via Internet
Termodinamika:

Sumber: http://www.freebookcentre.net/Physics/

## Minggu, 01 Agustus 2010

### Fisika untuk Universitas

Fisika untuk Universitas

Ditujukan untuk meningkatkan kualitas proses dan hasil perkuliahan Fisika di tingkat Universitas

Kelistrikan dan Kemagnetan

Topics covered: Course introduction

Instructor/speaker: Prof. Walter Lewin

# Syllabus

## Course Meeting Times

Lectures: 3 sessions / week, 1 hour / session
Recitations: 2 sessions / week, 1 hour / session

## Course Description

In addition to the basic concepts of Electromagnetism, a vast variety of interesting topics are covered in this course: Lightning, Pacemakers, Electric Shock Treatment, Electrocardiograms, Metal Detectors, Musical Instruments, Magnetic Levitation, Bullet Trains, Electric Motors, Radios, TV, Car Coils, Superconductivity, Aurora Borealis, Rainbows, Radio Telescopes, Interferometers, Particle Accelerators (a.k.a. Atom Smashers or Colliders), Mass Spectrometers, Red Sunsets, Blue Skies, Haloes around Sun and Moon, Color Perception, Doppler Effect, Big-Bang Cosmology.

There is a build-your-own-motor contest as part of this course (see Calendar).

## Textbook

Giancoli, D. C. Physics for Scientists & Engineers. Vol. 2. Prentice Hall.

------. The Study Guide and Student Solutions Manual. 3rd ed. Prentice Hall.

## Lectures - Homework - Solutions - Exams - Quizzes - Grades

There will be 36 lectures, 10 problem sets, 3 exams during regular lecture hours, and a 3-hour final. Weekly 15-minute quizzes will be given in recitations. During exams, I expect you to know all material covered in (i) the lectures, (ii) the reading assignments, (iii) the problem sets and (iv) recitations. When the need arises, Lecture Supplements (see Lecture Notes) will be made available.

Please hand in your homework on the due dates before 4 PM. Three problems, randomly chosen, will be graded. Solutions will be made available on the day after the due dates.

The homework counts for 10%, the weekly quizzes for 15%, each exam for 15%, and the final exam counts for 30% of your course grade.

There will be no make-up exams!

A missed homework, quiz or exam counts as a zero. Only in case of verifiable illness can you be excused from taking one of the 3 exams. If at all possible, this should be done before the exam.

## Recitations

There are 28 recitation sections. If for any reason you want to change section, please see the Course Manager; she will accommodate you as much as possible.

Ucapan Terima Kasih Kepada:

1. Para Dosen MIT di Departemen Fisika

a. Prof. Walter Lewin, Ph.D.

b. Prof. Bernd Surrow, Ph.D.

#### Staff

Visualizations:
Prof. John Belcher

Instructors:
Dr. Peter Dourmashkin
Prof. Bruce Knuteson
Prof. Gunther Roland
Prof. Bolek Wyslouch
Dr. Brian Wecht
Prof. Eric Katsavounidis
Prof. Robert Simcoe
Prof. Joseph Formaggio

Dr. Peter Dourmashkin
Prof. Robert Redwine

Technical Instructors:
Andy Neely
Matthew Strafuss

Course Material:
Dr. Peter Dourmashkin
Prof. Eric Hudson
Dr. Sen-Ben Liao

#### Acknowledgements

The TEAL project is supported by The Alex and Brit d'Arbeloff Fund for Excellence in MIT Education, MIT iCampus, the Davis Educational Foundation, the National Science Foundation, the Class of 1960 Endowment for Innovation in Education, the Class of 1951 Fund for Excellence in Education, the Class of 1955 Fund for Excellence in Teaching, and the Helena Foundation. Many people have contributed to the development of the course materials. (PDF)

2. Para Dosen Pendidikan Fisika, FPMIPA, Universitas Pendidikan Indonesia.

Terima Kasih Semoga Bermanfaat dan mohon Maaf apabila ada kesalahan.