Understanding magnetic field, magnetic flux, and magnetic flux density

 Analogies are often effective in explaining matters relating to physics most especially when two or more terms sounds quite similar and complicated. In our previous post, we were able to explain speed, velocity, and acceleration using analogies and in today's post, we have yet another group of physics philosophy which sounds quite similar and complicated to understand. So we'll try and break it down by applying it rules to a more common objects. Let start by their definitions.

Magnetic field

A magnetic field is a region around a magnet or a current-carrying conductor, where a magnetic force is experienced or where a magnetic force exist. The direction of this magnetic field is represented by magnetic field lines.

Magnetic flux

The magnetic flux  is therefore proportional to the number of magnetic field lines passing through a magnetic field. For simplicity sake, just view the magnetic field lines as just the individual lines, then view the magnetic flux as the whole lines put together. The magnetic flux determines the strength of a magnetic field, i.e the more the magnetic flux set up, the stronger the magnetic field. Therefore, the magnetic flux is the net number or quantity of the magnetic field lines set up or produced in a magnetic field.

Magnetic flux density

This is defined as the magnet flux per unit area in a given magnetic field. While the magnetic flux determines the total strength of a magnetic field, the magnetic flux density determines the strength of a magnetic field just IN A GIVEN AREA. 

Now let move to the analogies.

Magnetic field: Let use a standing fan as an example. When you switch on the fan, it will blow the air around itself and you will feel the air. When you move closer to the fan you will feel the air pressure more intense. When you move farther away from the fan you will feel the air pressure lesser and as you continue to move away, the air pressure diminishes. Now let take the region that you experienced the air as fan field. If we are to define the fan field, we would say that the fan field is a region that a fan force(which is air) is experienced. Comparing it to the magnetic field, the magnetic field is just a region that a magnetic forced is experienced. But we humans cannot experienced a magnetic force but metals do.

Magnetic field lines: The standing fan is pushing the air towards a specific direction. But can we see it. No. But we can thus feel it. In fact if we were to draw lines representing the direction of the air, all we have to do is we will just try to visualize where we're recieving the breezes from and then draw an imaginary line showing the direction of the air. That is what magnetic field lines is all about. Magnetic flied lines(or magnetic lines of force) is just an imaginery line that shows the direction in which a magnetic force is comming from.

Magnetic flux:  A magnetic flux is represented to be the whole magnetic lines of force put together. Let consider a moment when the fan blades rotate at high speed, we will notice that even if we move farther away from the fan and in a slightly different direction, we will still feel the air intensely and the number of our imaginary lines will appear to be much because we will be receiving the air from all directions. So likewise, when the magnetic field is stronger, it will generate more magnetic field lines which will increase the magnetic flux. 

Magnetic flux density: To understand magnetic field density, let take a different approach. Let use the aspect of population density. The population density of a country is just a net number of people living in a particular country(maybe china). So the magnetic flux density is the amount of magnetic flux present in a given area. NOTE; "a given area" in a magnetic field not the whole magnetic field area. Just as the population density of a country can be greater or less than the one in another country. Likewise, the magnetic flux density in a given area can be greater than the one in another area. Consider when you stand by the side of the fan,, and when you stand in front of and when you stand at the back of the fan. You won't receive the same intensity of air, because the air density  varies from region to region.

 

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Why do birds and squirrels not get shocked by the high voltage power lines

Do you sometimes wonder why birds and some other animals like squirrels, sit and play over high voltage transmission lines without getting electrocuted? Our curiosity can go as far as making us assume that birds and squirrels feets are covered by strong insulators, or their body are resistance to electricity. The fact is that none of these assumptions are basically true because the reason why this happens is not owing to any special abilities. Birds or squirrels are absolutely not immune to electric shock( as you see in the image below). Here is what really happens.

photo of a dead bird hanging on a transmission pole

What is electric shock or electrocution: Electric shock is the sudden discharge of electric current into the body which can cause severe injury or a permanent damage to the body. Electrocution is when the victim dies from it at that point. For us to know why current isn't flowing through birds or squirrels sitting on a high voltage wires, we first have to know the three things needed for electric current to flow in the first place.

What is needed for current to flow 

For electric current to flow continuously, there must be: 

• A voltage source: Voltage is what provides the electromotive force for electrons to flow round a circuit. Just like a water pump is needed to provide the pressure needed to pump water through a pipe, so in the case of electricity, voltage is what provides the drive force for electric current and it always  relative  between two point. You'll never see a battery or an AC generator having just one terminal, it should have two active wires or terminals.

• A closed circuit: For electrons to flow continuously, they must be a  path, and that path is called a circuit. But electrons doesn't have infinite sources and destinations so a closed circuits provides a complete path for electrons to flow round a conductor. It doesn't matter the type of current, whether it an alternating current(AC) or a direct current(DC) they all require a closed circuit.

• A path of NO or relatively LOW resistance: There is practically no conductor with zero resistance, but for electric current to flow the resistance on a circuit must not be high enough to completely stop the flow of current in that circuit. Electric current highly prefer the path of lower resistance, that means a very least amount of current will flow in a in a path filled with electrical resistance.

Each of these 3 criteria plays a role on why birds and squirrels do not get electrocuted when playing on what suppose to roast them to ashes. Let explore.      

POINT 1:   ONE POINT CONTACT - As we’ve already learned, electricity requires a complete path (closed circuit) to continuously flow. Without two contact points on the body for electric current to enter and exit respectively, there is no hazard of shock. This is why birds and squirrels can safely rest on high-voltage power lines without getting shocked because they make contact with the circuit at only one point. When current is generated from the source (power plants) to the transmission lines, it follows a loop pattern. From the  live wires to different loads (transformers, home appliances) and then the earth wire(or ground) acts as the return path for this current to flow back to the source . Birds or squirrels do not take part in this loop because they always land on either of these wires. 

POINT 2: In order for electrons to flow through a conductor, there must be a voltage present to motivate them. Voltage, as you should recall, is always relative between two points. There is no such thing as voltage ”on” or ”at” a single point in the circuit, and so the bird contacting a single point in the above circuit has no voltage applied across its body to establish a current through it. Yes, even though they rest on two feet, both feet are touching the same wire, making them electrically common. Electrically speaking, both of the bird’s feet touch the same point, hence there is no voltage between them to motivate current through the bird’s body.

For schematic view of both scenario, see this diagram:

As we can see that the safe bird, appears to be electrically common.

POINT 3: Birds,  squirrels and even some other animals have a rather higher resistance to electricity. As earlier mentioned, electric current flow chooses the path of lower resistance. Birds do not offer an easy path for current to flow due to it high electrical resistance, so current bypasses the birds and chooses the path of lower resistance which are the copper or aluminium cables.

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Which class of software really controls the hardware? The firmware or the OS

 

When defining an 'operating system', you'll probably hear a part that says that an OS is a software program that communicates with the  hardware and also manages the hardware resources. This might often sounds contradictory to what you might have earlier read about a firmware sometime ago(probably), that a firmware is a software program or set of instructions programmed on a hardware device. This therefore raises this question, which of the software categories really controls the hardware, is it the firmware or the operating system? Or what is the difference between the firmware and the Os.

Definition of Operating system

 An OS(operating system) is a system software that manages the computer hardware resources, interfaces between the hardware and the user, and provides a framework for other programs and applications to run and function effectively.

        An OS provides the base management of a computer in general, it controls other computer peripherals via device drivers and also creates an environments for other applications to work via application programming interfaces. Operating systems are complex forms of software that uses graphical user interfaces(GUIs) for easy communication between the hardware and the user. 

Definition of Firmware

A firmware is a specific class of software or a piece of code programmed and embedded on a specific hardware component, that usually provides a low-level control for these component.

 How do I mean by a 'specific hardware component'? While an OS is a software that controls and manages the work of the entire system, the firmware is a software built and intended for a certain piece of a hardware or a hardware component, that provides linkages to how the hardware will communicates with other hardware in a system. It contains the logic codes that communicates directly with the hardware and provides a foundation layer for the OS to take over.

THE CONCEPT: The computer hardware or any kind of digital devices contains programmable microchips that are built on  orders of 0s (zeros) and 1s(ones). The concept of the 0s and 1s just refer to the ON and OFF state of the MOSFETs that actually made up these chips. For example 11000111 is an ON and OFF digital signal of the chip that can signify a piece of code that tells a computer what to do when a certain key is pressed. These type of codes are often written in binary formats or machine languages and are called  low level languages, so a type of software program  needed to communicate directly with the hardware itself must understand and support these binary format. That is when a firmware comes in.

 To have a clearer picture of what these software really does to a hardware, let see the many  classes of hardware devices concerned.

A remote control is an example of a device that requires firmware to turn the button matches into series of infrared beams signals that a TV can detect and process. The TV on the other hand, also contains firmware on it mother board that tells those ICs  how to interpret these infrared beams to digital signals for the screen. The screen also contains a firmware that helps to decode the digital signals that sent over a HDMI to create the images you see on the screen and display meaningful data that humans can understand. I guess humans also have firmware too that enable them to understand these data... Just kidding.

A traffic light also has a firmware that gives the instructions in form of codes, telling it to change the light at regular intervals. A firmware also provides various controls and automation for washing machines.

A computer is one example of a system that uses both an OS, and a firmware. The firmware of a computer is also called a BIOS and it enables the computer to perform certain operations as soon as it is turned ON. The principal job of a computer's BIOS is to govern the early stages of the startup process, ensuring that the operating system is correctly loaded into memory.

The operating system is the major software program that runs a computer throughout it operations. But what will even tell the processors, the hard drives, the screens, the keyboards etc(which are hardwares that are build on 0s and 1s)  that you want to startup the computer? That is the work of the computer BIOS. In fact, various hardware in the computer likewise has their individual firmware that direct them on how to connect to other hardware; for example, a processor(otherwise called cpu) without a firmware programmed on it won't even know how to detect a hard drive or network card in the mother board. If your hard drives in turn didn't have any firmware embedded on them, they won't even know how to spin fast, or when to stop. 

On a robot, there is likely an operating system running a program which operate the hands, a program which operates the legs, speakers transmitters etc.These OS will create an environment for the programs to switch very fast and it will seems like the programs are executing all at the right time.

A mobile phone though, uses the aspect of a firmware and an OS differently. A firmware is a separate thing in a general purpose computer whereas in a mobile phone it is part of the OS.

These examples shows that operating systems are needed when multiple programs are to run on the same system. And the OS manages the hardware in that it will provide a graphical users interface for the user to communicate with the hardware. A firmware functions in that it is very closely tied to the particular hardware components of a device, and it provides linkages on how a particular hardware part is to communicate with other hardware.

SUMMARY

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IC, microchip and processor - Do they mean the same thing?

                  

In the field of mordern day electronics and computer hardware systems, the names IC, Chip, and processor are very often used. But do they really mean the same thing? Are they different from each other? or Is there any specific situation you can interchange the names? Let find out.

Integrated Circuit: An Integrated circuit (Or simply IC) is an electronic component that is formed by an interconnection of series of other electronic components and circuits, fabricated as a single unit and usually laid on a semiconducting waver e.g silicon.

Different sizes of integrated circuits

Integrated circuits mounted on a PCB

      The constituent of an IC can contain as much more than thousands to millions of  electronic components,  like resistors, capacitors, diodes, transistors etc, all assembled together and arranged in series of mini circuits like flip flops, logic gates, Op-amps etc.

 The revolution of integrated circuits paved way for digital electronics and modern technology because multiple millions of electronic component can be made so tiny that it can be fabricated into just one flat component. Integrated circuit are usually embedded on a chip of silicon material, sometimes known as silicon wafers.

A slice of Silicon wafers

Microchip: The word "chip", is used simply to denote a small piece or a small slice of something, be it a potato chip, an ice chip or (in the case of electronics) a silicon chip. So when ICs  are sometimes nicknamed as microchip or chip, it simply because they are build on a small piece(or a small chip) of a semiconductor material, called silicon wafers. Ordinary chips are different from microchips. From the prefix   "micro", that means they are very tiny categories of electronic chips.

          Note that the silicon wafers are not the IC packages themselves.  To be precise, the silicon wafers is a material used to fabricate the constituent of the IC i.e the transistors and resistors. The black plastic packages just form an enclosure to protect the main constituent of the IC from excessive heat.  So if someone  refer to the whole package as chip, or IC, it all means the same thing. It simply a collection of different miniaturized microelectronic component, embedded on a chip(small piece) of silicon wafers.  

Processor:  The processor or CPU(central processing unit) or microprocessor is the brain of every digital device. It is a microelectronic chip(or IC) that resides in a computer and some other digital devices and it responsible for processing data in form of logic gates and carrying out operational instructions. The processor controls other part of the circuits, and does other basic mathmatical calculations in form of binary codes( 0s and 1s).

A processor can contain up to 2billion MOSFETs, arranged in order of flipflop circuits, logic gates, NAND and NOR gates, used to perform powerful computations. In the case of modern day technology, a single processor can be made up of multiply cores which all work together to operate and carry out powerful calculations at a very high speed. That is why in some computers or even smartphones, it will be specified that it uses a dual core or a quad core processor.

Intel core i9 processor

A computer CPU

Processor on a computer motherboard

So a processor is a class of integrated circuit that serves as the control unit of other part of the circuitry. It is the most critical section in a mother board and it act as the brain of the any digital device because it's responsible for carrying out data processing and other basic computations which makes the device smart. There are so many other ICs in a digital circuits that perform other functions  other than computations such as the flash ICs, used  as memory storage device, the RAM, the power IC, oscillator ICs etc but they do not act as the brain of the device. Since the processor is just a type of  integrated circuit, therefore, all processors are ICs but not all ICs are processors because not all ICs act as the brain of a computer.

SUMMARY

An Integrated Circuit (IC) can come in classes of memory chip, configuration chip, logic chip or microprocessor chip. It just an assembly of various electronic component fabricated as one unit.

A Chip or microchip is also a term given to an IC with respect to the fact that it is constructed with a small piece(or a small chip) of a semiconductor material called 'silicon wafers'.

A processor is a type of integrated circuit that act as the brain of digital electronic devices. It carries out data processing in form of binary codes. And just as all cars are motor vehicles, but not all motor vehicles are cars, so all microprocessors are integrated circuits, but not all integrated circuit are processors.

FACT -  Advancement in science today has even made it possible to implant microelectronic chips into the body of living things like humans and animals, sometimes for health issues or for research and discoveries. For example, a very tiny piece of microchip can be implanted into a human body, to monitor the action of blood cells. Or a tracker chip can be implanted on an animal skin to track it behaviour and immigration factors.  

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What is conventional current and why is it opposite to electron flow

Many students of physics and electrical engineering are confused by the idea of conventional current. If current is due to the flow of electrons, and direction of flow of electrons is from negative to positive, then what's with this conventional current of a thing, and why is it opposite to electron flow. 

To understand this post fully, I would recommend you first read about the concept of charged particles  in my previous post on why is it said that electrons are negatively charged. It will give you the ground basis on why it was necessary to introduce conventional current notation. 

This post will explain all you need to know about conventional current and why it opposite to electron flow. But first, let make sure we're on the same page by defining what electric current is.

What is electric current

When defining electric current due to current flow in metallic conductors, we would say that electric current is the flow of electrons. But the story sounds different when we consider the particles actually moving in electrolytes, (for e.g when a voltage source is applied to a glass of salt water,  what will happen is that positively charged sodium ions will move toward the negative terminal while negatively charged chloride ions move toward the positive terminal). This tells us one thing, that charged particles, which could be electrons, protons, ions, holes or both electrons and ions is what constitute current flow. 

      Electric current is thus the measure of flow of electric charge (or charges) through a conductor. But what direction do the charges actually flow to in terms of origin and destination?

What is the direction of electric current

 Benjamin Franklin in his experiment with static electricity, discovered that when a wax and a wool tend to attract themselves after they were rubbed together, it entails that bunch of invisible fluids (later discovered to be electrons) were trying to regain it former balance after they were displaced by the action of that rubbing. This invisible fluids will always flow from the region of excess(denoted to be positive) to the region of deficit(denoted to be negative). Expanding further with the wax and wool experiment, when wax and wool were vigorously rubbed together, invisible fluids will forcefully be displaced from one of the material to another. But from which material to which material?  Franklin then suggested that the coarse wool removed some of this invisible fluids from the smooth wax during the process of rubbing, causing an excess of fluid on the wool and a deficiency of fluid on the wax. The resulting disparity in fluid content between the wool and wax would then cause an attractive force, as the fluid tried to regain its former balance between the two materials.

Advancement in scientific research further made it clear that these ”fluid” was actually composed of extremely small bits of matter called electrons, and that they were actually displaced from the wool to the wax not from the wax to the wool as Franklin suggested. So the wax was the actual region of excess (or positive region) and the wool was the actual region of deficit(or negative). In other words, Franklin's suggested region of excess (which was the wool) was clarified to be the region of deficit and his suggested region of deficit(which was the wax) was clarified to be the real region of excess. So Franklin's conjecture of direction of charged particles was the other way round. What a confusion.

Why was a convention needed?

First of all, what is a science convention? A science convention is an international conference, that holds to set up a precise and generally acceptable standards in science parameters and unit of measurement.

By the time the true direction of electron flow was discovered, the nomenclature of ”positive” and ”negative” had already been so well established in the scientific community that no effort was made to change it, although calling electrons ”positive” would make more sense in referring to ”excess” charge. You see, the terms ”positive” and ”negative” are human inventions, and as such have no absolute meaning beyond our own conventions of language and scientific description. Franklin could have just as easily referred to a surplus of charge as ”black” and a deficiency as ”white,” in which case scientists would speak of electrons having a ”white” charge (assuming the same incorrect conjecture of charge position between wax and wool). However, because we tend to associate the word ”positive” with ”surplus” and ”negative” with ”deficiency,” the standard label for electron charge does seem backward. Because of this, many engineers decided to retain the old concept of electricity with ”positive” referring to a surplus of charge, and label charge flow (current) accordingly. This became known as conventional flow notation.

Hope you liked this post and also understands the reason why what they call conventional current exist and why they say it opposite to electron flow. If you have any doubt or question concerning this article, just include it in the comment box below and don't forget to subscribe if you want to be receiving notifications for interesting post like this one.

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