Electricity and magnetism in technology



Electricity and magnetism for electrical engineers.–Portal.com

Electricity and magnetism explained.
– Picture from electricityforum.com

THIS lecture number 12 is on Electricity and Magnetism in association with technology in the Science in Action series. Welcome once again as we missed last Friday’s lecture on this topic as we all understand education is a life-long process.
Have you ever imagined that you are also a generator of electricity just like an ant is as well? In fact, about every living thing is a generator of electricity. With electricity you will not go wrong with a dual property of magnetism. Magnetism is an associated property of electricity so together they go hand in hand. This presupposes, when you generate electricity, you are also generating magnetism. This is the imperative property that commands a self-propagating trait seen in all electromagnetic waves of transverse waves. That property is explained appropriately in the concepts of permittivity and permeability.
In an overall view it can be seen that with electricity generation, there is always a magnetic field attached to it. Electricity is measured in Wattage or watts and the magnetism has no special unit but is a vector field measured in H as taken from the base unit ampere per meter (A/m) and B as magnetic flux density measured in tesla as taken from the base unit kilogram per second squared per ampere.
The following lecture will define the working of electricity and magnetism to your understanding and comprehension.
Electricity and magnetism appear in a pair as mentioned in the above preamble simply because they work in pair and not separately or not in isolation. This is like a positive charge is attracted to a negative charge. Only then a chemical reaction will take place. Similarly, a north pole will get attracted to a south pole because of electricity and magnetism in that protons from the positive terminal travel out to the negative terminal as shown by the magnetic field line.
When electricity flows, which means

Identifying ions and ammonium chloride.
– Picture from nagwa.com

Transformer and magnetic field/flux through the iron core.
– Picture from physics.stackexchange.com

Magnetic dipole and dipole moment.
– Picture from khanacademy.com

flow of electrons through a conducting pathway called a conductor or specifically an electrical conductor, it generates a field called a magnetic field around the conductor in which it is flowing. So to test this, one can hold a magnetic needle like a compass close to a conducting wire of a direct current (dc) battery power and see that the needle will deflect to clockwise or an anti-clockwise direction depending on the direction of the flow of the electric current. When you change or swap the battery terminals and observe the deflection on the magnetic needle, the direction will be reversed also. This supports the idea that electricity and magnetism work together in pairs.
Similarly, when you move a magnet into and out of a coil of wire, you will surely generate electricity. That is because the magnetic field flux of the magnet has caused electrons in the wire to move. Also, when one moves the coil of wire around a magnet, electricity will also be generated on the wire because the work done on the magnetic field flux will provide the force to make the electrons to move. More coil of wire will mean more current and also, more rotations around the magnet will also mean more electric current.
In brief, a change in electric current has caused a magnetic field. Also, a change in magnetic field will cause an electric current to flow.

Electricity and magnetism lesson.
– Picture from study.com

These two forces make up one of the four dominant natural forces in nature. This force is called the electromagnetic force. The electricity and magnetism cannot operate in isolation and that is the reason for having the topic Electromagnetism (EM) in Physics.
In the universe there are only two charges, and these are the positive charges produced by the protons and negative charges produced by the electrons. These charges are equal or balanced in nature. That is why we have a zero net-charge in the universe. There are many charges in the in nature or universe, but they appear in very tiny fractions of a second and these are in nanoseconds or magnitudes and then they disintegrate.
The electricity will produce a north and a south pole. That is there will be a tendency for protons to move from a positive terminal to a negative terminal. To demonstrate if you take some iron fillings and decide to shake inside a magnetic field exerted by a magnet, you will find that the iron fillings will be arranged according to the field lines of the magnet.
There are static electric currents that are also available in nature. These are charged objects exerting magnetic fields. This is rather not caused by the flowing electric current, but somewhat by the excitations of electrons and protons found inside that object. For instance, if you rub a plastic ruler with a cotton wool or your hair, you are going to transfer charges from one object to another. We choose plastic rulers because they have macro or big molecules made from polymers that can easily be rubbed off to create those surfaces which are charged. Now when you take that ruler to a smaller neutral object nearby, that small object will get attracted to the charged object which is the plastic ruler. This is called static electromagnetism. Static electricity is when an electric charge, whether a positive or a negative charge remains on a surface until it is in contact with an electric current to move on.
The electric charge is measured in coulombs and electric current is measured in amperes or amps. The magnetic charge is measures in terms of a magnetic monopole. This is a hypothetical measurement. A magnetic dipole is a measurement of a closed loop of an electric current. This is the current contained within the two poles (north and south) and so the net charge is down to zero and the magnetic moment attains a constant value.
Magnetic moment as defined by Wikipedia is “the magnetic strength and orientation of a magnet or other object that produces a magnetic field.” The magnetic field is measured in Tesla.
My prayer for PNG today is: “Just as the rain falls to water the earth, just as a seed becomes bread, My Word upon you can never return. Until my longing is filled…Come to the Water, you who are thirsty, though you have nothing, I bid you come…”

Next week: Sciences of the Electromagnetism and Technology

Michael John Uglo is the author of the science text book “Science in PNG, Pacific, Asia & Caribbean”
and a lecturer in Avionics, Auto- Piloting and Aircraft Engineering.

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