I was looking at a lot of YouTube videos today that would give me me clue to what electromagnetism is, how it behaves and why it exists.
For the first two questions I was able to get some reasonable explanations, but for the why, well .. lets say it was pretty fuzzy.
In the process, I got to brush up on the basic laws of electricity that we learn at school and I should say, though they made sense, it still sounds like voo-doo sometimes.
Now I am clear on:
The left hand rule that gives the direction on the magnetic field that would be generated by flowing Electrons. Where the thumb points to direction of flow of electron, the fingers would point to the direction of field lines of the magnetic field.
The right hand rule is the same, but is used for positive charge flow direction or the conventional current direction.
Oersted was the guy who first discovered that flowing electrons generate a magnetic field.
The same left hand rule can be used to find the direction of the N pole that would be generated inside a solenoid, except in reverse. That is, if the curved fingers pointed in the direction of flow of electrons, the thumb would point to direction of the N pole! Isn't that simple!
Another thing I learnt today was that Ampere discovered that two wires carrying current in the same direction would attract each other. Here is a fantastic video that makes it all clear.
Also the thing to note is that if a magnetic line of force is say, pointed towards the right, the north pole of a compass will also point to the north. This is the first time I see a circular magnetic field, and here is a video that clear shows that.
Apart from that I also recalled how a battery works, How but not yet Why deeply enough, that's why I am going from the basics. And here is nice cool video that shows how a car battery works.
I also saw how the electron was discovered by J J Thompson, and then how the atom model was given by Rutherford. Here is a nice video for that. And then I saw how the idea of electricity as a invisible fluid that present in all matter is the reason why so many of the terms that are used to describe electricity are like current, charge (yes even that!), flow from positive to negative and the like. And, you guessed it, here is the video.
Last but not the least, I also saw the Faraday's law of electro-magnetic induction. Which is that a changing magnetic field also generates an Induced current is nearby conductor not only the other way around as was previously believed. That is something extraordinary to come up with really. But I am not clear on why that happens at an atomic level, and I am told that its basically quantum-electro-dynamics as explained by the likes of Feynman. Cuz intuitively it doesn't make sense that an electron, an electric charge would be affected by a magnetic field and then start flowing!!!
The unified theory of strong and weak electromagnetic forces was something cool look at. The video is at the same place where the Rutherford's story was shown.
Oh and there was also this video that said that the reason for the magnetism generated by flowing electrons was their spin. When electrons flow they are all somehow spinning in the same direction, just like in natural magnets, causing a magnetic field. At first glance it makes sense, but something doesn't fit here. Like, is there a polarity of charge even on an electron?If so, then the electron is not the basic elementary charge, the charge is actually sitting on an electron. Then what makes up charge? Is there a relation between where the charge is on an electron and how the electron is spinning? Cuz only if that relation is same, will all electrons be spinning uniformly.
But here are the questions:
First off, why is the measure of force of a magnetic field on an unit charge taken as the basis for calculating magnetic field strenght. F = BqvsinTheta or F = BIlsinTheta is a famous formula, used to calculate B in terms of Ns/Cm or Tesla. But Why oh why would they take a electric charge as the basis for magnetism? Is it cause of its almost non existent weigth (in case of an electron)?
Like charges repel, unlike charges attract. Agreed. But why does an electrical property of a particle or matter, result in the physical motion or manifestation? There are lot of purely physical forces like, angular momentum that a fundamental, electricity cannot explain them, hell they cause a lot of things to happen in the electric realm. Why are there some physical forces that cannot be explained by electricity, but physical forces like attraction or repulsion ie physical movement is explained by it. Basically, why would electric property of a body make it to react physically. The chemical composition doesn't make it happen, that too is at atomic level then why this?
Third is why does a wave move or propagate? As I understand, the vibrating electric charges cause a field to radiate. That doesn't tell me anything. The charges are in their place, they are vibrating on the same spot, their field of influence is limited, we all know that, then why does a fluctuating field of influence propagate?
Last but not the least, I repeatedly hear that electricity and magnetism are two aspects of the same physical phenomenon, without any clue to what that 'phenomenon' actually is.
Answer soon I hope.
Friday, September 17, 2010
Tuesday, September 14, 2010
Today's Topic: Charge
Search : define:charge
Results:
All the word meanings charge - like cost, move forward etc.
Wikipedia says about charge:
More abstractly, a charge is any generator of a continuous symmetry of the physical system under study. When a physical system has a symmetry of some sort, Noether's theorem implies the existence of a conserved current. The thing that "flows" in the current is the "charge", the charge is the generator of the (local) symmetry group. This charge is sometimes called the Noether charge.
Wikipedia says about electric charge:
Charge is the fundamental property of a matter that exhibit electrostatic attraction or repulsion over other matter.
Electric charge is a physical property of matter which causes it to experience a force when near other electrically charged matter.
The electric charge is a fundamental conserved of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic interaction. The interaction between a moving charge and an electromagnetic field is the source of the electromagnetic force, which is one of the four fundamental forces.
The electric charge of a macroscopic object is the sum of the electric charges of the particles that make it up. This charge is often zero, because matter is made of atoms, and atoms all have equal numbers of protons and electrons. More generally, in every molecule, the number of anions (negatively charged atoms) equals the number of cations (positively charged atoms). When the net electric charge is non-zero and motionless, the phenomenon is known as static electricity. Even when the net charge is zero, it can be distributed non-uniformly (e.g., due to an external electric field or to molecular motion), in which case the material is said to be polarized. The charge due to polarization is known as bound charge, while the excess charge brought from outside is called free charge. The motion of charged particles (especially the motion of electrons in metals) in a given direction is known as electric current.
Unit of charge is coulomb defined as: The coulomb is defined as the quantity of charge that has passed through the cross section of an electrical conductor carrying one ampere within one second.
After finding the quantized character of charge, in 1891 George Stoney proposed the unit 'electron' for this fundamental unit of electrical charge. This was before the discovery of the particle by J.J. Thomson in 1897. The unit is today treated as nameless, referred to as "elementary charge", "fundamental unit of charge", or simply as "e".
Static electricity and electric current are two separate phenomena, both involving electric charge, and may occur simultaneously in the same object. Static electricity is a reference to the electric charge of an object and the related electrostatic discharge when two objects are brought together that are not at equilibrium. An electrostatic discharge creates a change in the charge of each of the two objects. In contrast, electric current is the flow of electric charge through an object, which produces no net loss or gain of electric charge. Although charge flows between two objects during an electrostatic discharge, time is too short for current to be maintained.
What wiki says about conservation law:
What wiki says about symmetries in physical systems:
In physics, symmetry includes all features of a physical system that exhibit the property of symmetry—that is, under certain transformations, aspects of these systems are "unchanged", according to a particular observation. A symmetry of a physical system is a physical or mathematical feature of the system (observed or intrinsic) that is "preserved" under some change.
The transformations may be continuous (such as rotation of a circle) or discrete (e.g., reflection of a bilaterally symmetric figure, or rotation of a regular polygon). Continuous and discrete transformations give rise to corresponding types of symmetries. Continuous symmetries can be described by Lie groups while discrete symmetries are described by finite groups (see Symmetry group). Symmetries are frequently amenable to mathematical formulation and can be exploited to simplify many problems.
Invariance is specified mathematically by transformations that leave some quantity unchanged. This idea can apply to basic real-world observations. For example, temperature may be constant throughout a room. Since the temperature is independent of position within the room, the temperature is invariant under a shift in the measurer's position.
answers.com: columbia encyclopaedia says: charge, property of matter that gives rise to all electrical phenomena (see electricity). The basic unit of charge, usually denoted by e, is that on the proton or the electron; that on the proton is designated as positive (+e) and that on the electron is designated as negative (−e). All other charged elementary particles have charges equal to +e, −e, or some whole number times one of these, with the exception of the quark, whose charge could be 1/3e or 2/3e. Every charged particle is surrounded by an electric field of force such that it attracts any charge of opposite sign brought near it and repels any charge of like sign, the magnitude of this force being described by Coulomb's law (see electrostatics). This force is much stronger than the gravitational force between two particles and is responsible for holding protons and electrons together in atoms and for chemical bonding. When equal numbers of protons and electrons are present, the atom is electrically neutral, and more generally, any physical system containing equal numbers of positive and negative charges is neutral. Charge is a conserved quantity; the net electric charge in a closed physical system is constant (see conservation laws). Whenever charges are created, as in the decay of a neutron into a proton, an electron, and an antineutrino, equal amounts of positive and negative charge must be created. Although charge is conserved, it can be transferred from one body to another. Electric current, on which much of modern technology is dependent, is a flow of charge through a conductor (see conduction). Although current is usually treated as a continuous quantity, it actually consists of the transfer of millions of individual charges from atom to atom, typically by the transfer of electrons. A precise description of the behavior of electric charge in crystals and in systems of atomic and molecular dimensions requires the use of the quantum theory.
Questions:
It is clear that charge is the source of all electricity, but what is the source of charge?
As I see it now, charge is a form of quantification of energy. The what about electromagnetism?
Charge seems to be both the source and the victim of electromagnetism. But electromagnetism in itself is not clear. And also the concept of electric fields.
Another basic thing to study would be how is electric current or rather potential generated in a battery? That should give me some insights into the mathematical manipulations involved in simple electric charges keeping out the electromagnetism.
Conclusion:
The concept of charge and electromagnetism is deeply inter correlated. Hence should be studied together. Should continue the same tomorrow.
Results:
All the word meanings charge - like cost, move forward etc.
Wikipedia says about charge:
More abstractly, a charge is any generator of a continuous symmetry of the physical system under study. When a physical system has a symmetry of some sort, Noether's theorem implies the existence of a conserved current. The thing that "flows" in the current is the "charge", the charge is the generator of the (local) symmetry group. This charge is sometimes called the Noether charge.
Wikipedia says about electric charge:
Charge is the fundamental property of a matter that exhibit electrostatic attraction or repulsion over other matter.
Electric charge is a physical property of matter which causes it to experience a force when near other electrically charged matter.
The electric charge is a fundamental conserved of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic interaction. The interaction between a moving charge and an electromagnetic field is the source of the electromagnetic force, which is one of the four fundamental forces.
The electric charge of a macroscopic object is the sum of the electric charges of the particles that make it up. This charge is often zero, because matter is made of atoms, and atoms all have equal numbers of protons and electrons. More generally, in every molecule, the number of anions (negatively charged atoms) equals the number of cations (positively charged atoms). When the net electric charge is non-zero and motionless, the phenomenon is known as static electricity. Even when the net charge is zero, it can be distributed non-uniformly (e.g., due to an external electric field or to molecular motion), in which case the material is said to be polarized. The charge due to polarization is known as bound charge, while the excess charge brought from outside is called free charge. The motion of charged particles (especially the motion of electrons in metals) in a given direction is known as electric current.
Unit of charge is coulomb defined as: The coulomb is defined as the quantity of charge that has passed through the cross section of an electrical conductor carrying one ampere within one second.
After finding the quantized character of charge, in 1891 George Stoney proposed the unit 'electron' for this fundamental unit of electrical charge. This was before the discovery of the particle by J.J. Thomson in 1897. The unit is today treated as nameless, referred to as "elementary charge", "fundamental unit of charge", or simply as "e".
Static electricity and electric current are two separate phenomena, both involving electric charge, and may occur simultaneously in the same object. Static electricity is a reference to the electric charge of an object and the related electrostatic discharge when two objects are brought together that are not at equilibrium. An electrostatic discharge creates a change in the charge of each of the two objects. In contrast, electric current is the flow of electric charge through an object, which produces no net loss or gain of electric charge. Although charge flows between two objects during an electrostatic discharge, time is too short for current to be maintained.
What wiki says about conservation law:
In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves.
One particularly important physical result concerning conservation laws is Noether's Theorem, which states that there is a one-to-one correspondence between conservation laws and differentiable symmetries of physical systems. For example, the conservation of energy follows from the time-invariance of physical systems, and the fact that physical systems behave the same regardless of how they are oriented in space gives rise to the conservation of angular momentum.
What wiki says about symmetries in physical systems:
In physics, symmetry includes all features of a physical system that exhibit the property of symmetry—that is, under certain transformations, aspects of these systems are "unchanged", according to a particular observation. A symmetry of a physical system is a physical or mathematical feature of the system (observed or intrinsic) that is "preserved" under some change.
The transformations may be continuous (such as rotation of a circle) or discrete (e.g., reflection of a bilaterally symmetric figure, or rotation of a regular polygon). Continuous and discrete transformations give rise to corresponding types of symmetries. Continuous symmetries can be described by Lie groups while discrete symmetries are described by finite groups (see Symmetry group). Symmetries are frequently amenable to mathematical formulation and can be exploited to simplify many problems.
Invariance is specified mathematically by transformations that leave some quantity unchanged. This idea can apply to basic real-world observations. For example, temperature may be constant throughout a room. Since the temperature is independent of position within the room, the temperature is invariant under a shift in the measurer's position.
Similarly, a uniform sphere rotated about its center will appear exactly as it did before the rotation. The sphere is said to exhibit spherical symmetry. A rotation about any axis of the sphere will preserve how the sphere "looks".
The above ideas lead to the useful idea of invariance when discussing observed physical symmetry; this can be applied to symmetries in forces as well.
For example, an electrical wire is said to exhibit cylindrical symmetry, because the electric field strength at a given distance r from an electrically charged wire of infinite length will have the same magnitude at each point on the surface of a cylinder (whose axis is the wire) with radius r. Rotating the wire about its own axis does not change its position, hence it will preserve the field. The field strength at a rotated position is the same, but its direction is rotated accordingly. These two properties are interconnected through the more general property that rotating any system of charges causes a corresponding rotation of the electric field.
answers.com: columbia encyclopaedia says: charge, property of matter that gives rise to all electrical phenomena (see electricity). The basic unit of charge, usually denoted by e, is that on the proton or the electron; that on the proton is designated as positive (+e) and that on the electron is designated as negative (−e). All other charged elementary particles have charges equal to +e, −e, or some whole number times one of these, with the exception of the quark, whose charge could be 1/3e or 2/3e. Every charged particle is surrounded by an electric field of force such that it attracts any charge of opposite sign brought near it and repels any charge of like sign, the magnitude of this force being described by Coulomb's law (see electrostatics). This force is much stronger than the gravitational force between two particles and is responsible for holding protons and electrons together in atoms and for chemical bonding. When equal numbers of protons and electrons are present, the atom is electrically neutral, and more generally, any physical system containing equal numbers of positive and negative charges is neutral. Charge is a conserved quantity; the net electric charge in a closed physical system is constant (see conservation laws). Whenever charges are created, as in the decay of a neutron into a proton, an electron, and an antineutrino, equal amounts of positive and negative charge must be created. Although charge is conserved, it can be transferred from one body to another. Electric current, on which much of modern technology is dependent, is a flow of charge through a conductor (see conduction). Although current is usually treated as a continuous quantity, it actually consists of the transfer of millions of individual charges from atom to atom, typically by the transfer of electrons. A precise description of the behavior of electric charge in crystals and in systems of atomic and molecular dimensions requires the use of the quantum theory.
Questions:
It is clear that charge is the source of all electricity, but what is the source of charge?
As I see it now, charge is a form of quantification of energy. The what about electromagnetism?
Charge seems to be both the source and the victim of electromagnetism. But electromagnetism in itself is not clear. And also the concept of electric fields.
Another basic thing to study would be how is electric current or rather potential generated in a battery? That should give me some insights into the mathematical manipulations involved in simple electric charges keeping out the electromagnetism.
Conclusion:
The concept of charge and electromagnetism is deeply inter correlated. Hence should be studied together. Should continue the same tomorrow.
First Post
Hi,
As the title states, this is a blog about my journey through electronics.
I have studied electronics engineering, am familiar with the jargon but have always felt I dint quite catch the exact meaning of things. What the words really imply in the physical world. I have tried starting from scratch before but well, got lost and gave up after a point. This time I wanted to start a blog so that I could keep track of what I'm dong and keep a log for any future use.
So, here we go!
--
AJ
As the title states, this is a blog about my journey through electronics.
I have studied electronics engineering, am familiar with the jargon but have always felt I dint quite catch the exact meaning of things. What the words really imply in the physical world. I have tried starting from scratch before but well, got lost and gave up after a point. This time I wanted to start a blog so that I could keep track of what I'm dong and keep a log for any future use.
So, here we go!
--
AJ
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