Ohm's law was formulated by George Simon Ohm who studied electricity and after carrying out several investigations, in 1827 he discovered this law. This law relates the magnitudes of:
Ohm's law states that: the ntensity of electric charge is expressed in amperes (A), which circulates inside an electrical circuit is directly proportional to its electrical voltage and at the same time inversely proportional to its resistance. The law discovered by George Simon, as its name suggests, is represented in ohms (Ω).
Depending on the information we have we will apply one of the following formulas or others:
I V / R
V = I · R
R=V / I
Ohm's law helps us to find the power of a circuit, as power is the multiplication of voltage and current. A circuit is made up of atoms that can have positive or negative charges: protons (+) and electrons (-). In addition to these two atoms, we can find neutrons that have a neutral charge. Below, we can see a circuit.
The Ohm's law triangle is a trick to remember the formula. We only have to cover the variable we want to obtain.
Whereas in a direct current (DC) we find a continuous flow, that is to say, a constant current. In an alternating current (AC), as the name suggests, there are alternating current peaks at regular intervals.
We can find the current in parallel, which has two resistors and can flow through two paths.
Ohm's law can be found in any device that contains an electrical circuit, so we have it present in our daily lives both at home and elsewhere, either indoors or outdoors. An example of an application that we can see in our daily life is the refrigerator, in the moment in which it is connected to the electric current and receives the voltage conducting the current which helps to cool it, this law is already being applied.
The magnetic spectrum was discovered by Wilhelm Conrad Röntgen in 1895 and was responsible for producing electromagnetic radiation in the wavelengths that refer to X-rays. Before the electromagnetic spectrum, we can find the normal spectrum which was discovered by Isaac Newton in 1666, placing several lenses next to a prism and through it, he could see the different colors.
The electromagnetic spectrum is the grouping of all the forms in which radiant energy is found. This grouping of frequencies or lengths can be broken down into electromagnetic radiation. These two quantities are in relation to the speed of light.
C = constant, that is to say 3.00 x 108 m/s
λ = wavelength
f= frequency
Depending on what we want to obtain, we just have to isolate the letter.
Depending on the type of electromagnetic radiation, the electromagnetic spectrum can be divided into two groups:
Ionizing radiation:
Non-ionizing radiation:
Depending on the properties of the light waves, we can find different colors such as:
| Colour | Wavelength in 10-9m | Frequency (1012Hz) |
| Red | 780 – 622 | 384 – 482 |
| Orange | 622 – 597 | 482 – 503 |
| Yellow | 597 – 577 | 503 - 520 |
| Green | 577 – 492 | 520 – 610 |
| Blue | 492 – 455 | 610 – 659 |
| Violet | 455 - 390 | 659 – 769 |
Nowadays we can find the electromagnetic spectrum in a very common way. Some of the most common applications we can find are telecommunications, information transmission, radars...
Terrestrial magnetism is the presence of a magnetic field on Earth, creating a resemblance to a large magnet. The earth's magnetic field is produced by the formation of the spiral where we find Ampère's law that later originates an electric field, Faraday's law. In 1600 a doctor, William Gilbert, while carrying out a study on magnetism, discovered that the origin of magnetism was to be found in the planet itself, in the terrestrial sphere, which has a behavior very similar to that of a magnet, creating the theory of terrestrial magnetism.
The similarity between terrestrial magnetism and the magnet was discovered by primitive compasses, which is why the poles are given the names of the north and south poles. The distribution of the poles is not fixed as the axis is in motion causing an alteration of the earth's mass, which leads to variations in the location of the poles. In addition to the magnetic pole, there is the geographic pole, which, unlike the magnetic pole, is fixed. The angular difference between these poles is called declination.
The presence of the earth's magnetic field gives us the protection we need when we are exposed to radiation from outside the earth. This magnetic field acts as a barrier, filtering and retaining charged particles, this area of the atmosphere is called the Van Allen belt.
When particles come into contact with the earth's magnetic field, they produce various natural phenomena, such as the northern lights.
The layer above the dense inner core is composed of liquid iron, which rotates and shakes, causing an electric current, resulting in the geodynamo, which is responsible for maintaining the magnetic field.
For the earth's magnetic field to work properly we need the following properties:
Inclination = the magnetic field tends to tilt towards the magnetic north pole which rotates until it reaches the inclination of the magnetic equator.
Intensity= the intensity found at the poles ranges from 0.25 to 0.65 Gauss.
Bipolar = the magnetic field has two poles: the magnetic pole and the geographic pole, each of which has a north and a south pole.
Ampère's law is a law that is part of Maxwell's 4 equations, it replaced Biot Savart's law. This law allows us to calculate the magnetic field by means of electric currents. The law was discovered in 1826 by André Marie Ampère and connects the electric current intensity and the magnetic field it produces.
Unlike electric fields, magnetic field lines are not conservative, in other words, the circulation in a closed line is not zero. If the direction in which the currents circulate has the same direction as the direction of the surface vector, it will be positive. On the other hand, it will be considered negative if the direction is opposite.
Ampère's law allows us to know the magnetic field produced by the current by applying the following formula.
On the one hand, the first integral, that is to say, the left-hand part of the formula represents the circulation found in the field lines in their closed path. In addition, the dl refers to the tangent vector of the selected path at each point. On the other hand, the right-hand side of the formula refers to:
Maxwell later corrected Ampère's law, realizing that magnetic fields, like electric currents, change with time. So the updated formula reads as follows:
J= charge current
dS= vector perpendicular to the surface at every point
Ampère's law allows us to know the magnetic field of:
A conducting wire
A cylindrical wire of radius
A solenoid
This law can be used for electromagnets, generators, transformers, and motors.
The law discovered by André Marie Ampère can be applied to a solenoid in order to find the magnetic field inside it. This magnetic field is proportional to the current applied and to the number of turns per its length. The electromagnet is an application where we can clearly see this law since the magnetic field is equal to the sum of the magnetic fields of this spiral and this can be calculated with Ampère's law.
In addition to applying it to solenoids, it can also be applied to toroids.
The magnetic force found in a magnet refers to the residual effect of the magnetic force between moving charges.
The unit in the international system that refers to the magnetic force in a magnetic field is the tesla (T). In contrast, the strength of a magnetic field in a magnet is measured in gauss, as the unit is smaller
When we talk about the strength of magnets, we refer to magnetism. Magnetism is produced by the chargedmovement of electrons. These electrons can generate magnetism in two different ways.
By transition, it makes an orbital motion that circles around the nucleus.
By rotation, the electron moves on its own axis.
The magnetic force of the magnets, in the case where the velocity is perpendicular to the magnetic field, is obtained from the following formula.
Force = charge · velocity · field B
To know the direction of a magnetic field in a magnet, we must know the direction of the lines of magnetic force. We can obtain two versions of the right-hand rule:
1. The first version of the right hand
The law of the right hand is used to know the two types of direction, both the linear direction and the rotational direction. This rule consists of placing the first three fingers in the following position:
The index finger indicates the direction of the first vector of the vector product, this is represented by the symbol vector of u. By rotation, the electron moves about its own axis.
The middle finger (placed in the middle) refers to the second vector located in the vector v. By rotation, the electron moves on its own axis.
The thumb defines the direction and sense of this vector product. By rotation, the electron moves about its own axis.
2. The second version of the right hand
Place your right hand in the same way so that the fingers are in the same direction as the first vector of the vector product of u. By rotation, the electron moves about its own axis.
By closing the hand the fingers will tell us the direction of the second vector of the vector product of u. At the moment when the hand is closed, we get the angle or distance between the vectors, which is smaller. By rotation, the electron moves on its own axis.
Finally, the thumb tells us the direction and direction of the vector product.
Magnetic energy was detected at the time when James Clerk Maxwell investigated magnetism and electricity. This research intended to show that there was no connection between these two phenomena. In carrying out this study, he found that current was connected to magnetism (more specifically to fields). This discovery was followed by electromagnetic energy.
Magnetic force manifests itself in the form of magnetic fields. Magnetic force is the ability of the magnetic force to do mechanical work. Magnetic energy is the movement of the charge of the electrons in the different particles It is the movement that generates the current that produces the behavior of the electron like that of a small magnet.
The earth also possesses a magnetic field generating magnetic energy on the earth. This energy has a north pole and a south pole which, due to their interaction with the earth's atmosphere, produce natural phenomena such as the aurora borealis.
Magnetic energy or also known as magnetism is known by the force on which charge is in motion. Therefore:
F = magnetic force
qv= electric charge of the charge velocity vector
B = magnetic field vector
Magnetism is the phenomenon that allows us the presence of the force of attraction with magnetic elements (magnets). Magnetism can be found in:
- The compass
- Electrical transformers
- Hard disks
- Magnetic tomographs
- Maglev trains
- Northern lights
The relationship between electricity and magnetism lies in the electromagnetic force (electromagnetism). Electromagnetism was made known in 1821 by Michael Faraday. Furthermore, this electromagnetic force is the branch of physics that studies the relationship of charged particles to electric and magnetic fields.
Electromagnetism can be found in the following applications:
- Microphones
- Generators
- Electric motors
The movement of electrons (electric charges) is responsible for creating a magnetic field that subsequently creates magnets.
Within magnetic energy, we find different types of generators specializing in generating renewable electrical energy. The most common renewable energy obtained through magnets is wind energy, which uses permanent magnet generators.
Paramagnetism was discovered by Michael Faraday, who determined that most elements exhibit some level of paramagnetism. Paramagnetism is a type of magnetism that is weakly attracted by a magnetic field that is activated from the outside. This type of magnetism is found in paramagnetic materials.
Paramagnetic materials are materials that have permanent atomic dipoles which are placed linearly (parallel) in the direction of an external field. This material has a positive susceptibility, and when the magnetic field disappears, these materials lose all their magnetic properties. On the other hand, we can find unpaired electrons and other absent electrons.
Pauli paramagnetism appears in conduction, unaffected by temperature. The Pauli exclusion principle states that from one atom there cannot be 2 electrons that have the same 4 quantum numbers, in the other words, there must be opposite spins.
Paramagnetism in materials can be attracted by another magnet. However, it does not have the ability to attract another paramagnetic material. Paramagnetic materials have a small positive susceptibility (between 10-6 and 10-2).
Unlike diamagnetism, paramagnetic materials are affected by temperature. So, if the temperature increases, the order of the magnetic moments of the atoms decreases. This temperature is expressed by Curie's law.
X =C/T
X = magnetic susceptibility
C = Curie's constant (each material has a different one)
T = absolute temperature (K)
Another factor to be taken into account is the magnetization (M) which depends on the field strength
M = XH
Like diamagnetism, to know whether a material is paramagnetic or not, we must know the electronic configuration of the material in question In the case of paramagnetism, the electrons are unpaired.
Such as aluminum:
Aluminum has 3 electrons in the valence shell so it has one unpaired electron, which, as we have read, means that it is a paramagnetic material.
To know whether a material is paramagnetic or not, we have to look at the valence layer (the last layer, if it is unpaired, we will find that it is paramagnetic, in other words, paramagnetic elements have an odd number of electrons).
The valence layer is the last layer. The periodic table consists of 18 groups and 7 periods. Each time you change period you change layer.
Diamagnetism is a characteristic that a magnet possesses when the magnetization in the opposite direction to the application of the magnetic field is weak. Consequently, we can observe that material with this property, in other words, a diamagnetic material, is repelled by a magnet.
In 1778, Sebald Justinus Brugmans was the first to observe that two materials (bismuth and antimony), put up resistance to being attracted to magnetic fields.
Diamagnetism was discovered by Michael Faraday in 1845, with the help of the Faraday experiment, with a negative result (so this leads directly to Lenz's law). The acceleration of the external magnetic field slows down the electrons, so they oppose the action of the external field, weakening it.
Diamagnetism, like other types of magnetic materials, has several properties:
Diamagnetism can be in liquid, solid, or gaseous form.
The relative magnetic permeability of less than 1.
Its magnetic induction and susceptibility are negative.
Diamagnetic materials are notaffected by temperature.
Once the external field is removed, the material has no ability to retain magnetic properties.
To find out if a material is diamagnetic or not, we have to look at its electronic configuration, more specifically whether the electrons are unpaired or not. If the electrons are unpaired, the material will be paramagnetic, and if the electrons are paired, it will be diamagnetic.
The electronic configuration is the way in which the electrons are distributed within an atom, in which there are different layers. There are 7 energy levels: from 1 to 7, within each level, we can find 4 sublevels: s, p, d, and f.
Each sublevel has a maximum number of electrons.
| Sublevel | Nº electrons |
| Sublevel s | 2 electrons |
| Sublevel p | 6 electrons |
| Sublevel d | 10 electrons |
| Sublevel f | 14 electrons |
The best known diamagnetic materials are bismuth, helium, hydrogen, noble gases, gold, copper, bronze...
For example, bismuth has the following electronic configuration:
Bi = 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p3
Knowing that the atomic number is 83 and it is in group 15. Below we can see the atomic structure and the crystal structure.
Michael Faraday was a British-born physicist and chemist. In 1831, after conducting several experiments, he discovered electromagnetic induction. It was at this time that it was discovered that an electric field can be created from a varying magnetic field. It was this event that prompted Faraday's law and Lenz's law.
Faraday's law or also known as Faraday's law of electrolysis refers to the amount of mass that is proportional to some electricity.
Faraday's law states that the induced voltage across a coil is directly proportional to the rate at which the magnetic flux changes per unit time on a surface next to the circuit. At the moment the current is introduced, the magnetic field of the coil shows resistance to the change of flux. The negative sign of Faraday's law shows the direction of the induced current, also known as Lenz's law.
Next to Faraday's law, we find Lenz's law which, unlike Faraday's law, this law indicates the direction in which the current flows, as well as establishing the direction in which it creates resistance to change, in other words, the magnetic field produced by the induced current flows in the opposite direction to the field that was in the original field.
As we have seen above, Faraday's law is based on the voltage which is represented by: EMF (Ɛ).
EMF (Ɛ) = N · (∆ϕ/∆t)
EMF (Ɛ) = voltage of the coil
N = number of turns of the coil
dΦ = change of magnetic flux
dt = time lapse (∆t à 0)
To obtain Lenz's law we only have to change the sign of the calculation to negative since, due to its definition, Lenz's law refers to resistance to the change in flux variation. So the formula to obtain the value of this resistance is:
VƐ = - N · (∆ϕ/∆t)
Faraday's law and Lenz's law have many applications. All applications that have a connection to electrical technology depend on them. In the same way, we can use the laws in everyday life in various ways such as in:
Generator
Electric motor
Magnetic brake
Induction cookers
No.155-1, North Jingu Road
Yinzhou Investment & Business Industrial
Ningbo, PR China 315104
Via Industria 36, Ozzero
20080 Milan
Tlf: +39 (02) 94 00 137
Tlf: +39 (02) 94 00 609
Fax +39 (02) 9407178
E-mail: cristina@ima-italia.it
Avda. Cataluña, 5
08291 Ripollet (Barcelona)
Tlf: (+34) 93 579 54 15
E-mail: contacto@imamagnets.com
