O fieldmagnetic is a region of space where the electrical charges in motion are subject to the action of a magnetic force, able to change their trajectories. The magnetic field is the result of the movement of electrical charges, as in the case of a wire that conducts electric current or even in the oscillation of subatomic particles, such as the electrons.
Magnetic Field Properties
According to SI, the unit of measurement of the magnetic field is the tesla (T), in honor of one of the great scholars of magnetic phenomena, Nikola Tesla (1856-1943). the magnetic field é vector, as well as the electric field or the gravitational field, therefore, it presents the modulus, direction, and sense properties.
This type of field can be produced by magnets natural and artificial, made with conductive coils and coils. If you want to know more about the origins of the magnetic field, we suggest you read our article on magnetism and get all your questions answered.
Lookalso:Check out some essential tips to save electricity
As said, the origin of the magnetic field is in the movementof theloadselectrical devices. When the electric field oscillates in some region of space, this oscillation gives rise to a magnetic field oriented in a direction perpendicular (90º) to the electric field. To better understand the properties of the magnetic field, we make use of a feature known as induction lines, through it, we can better visualize the shape of the magnetic field.
magnetic field lines
The magnetic field lines are always closed, they Neverifcross, and the closer they are, the greater the strength of the magnetic field in that region. In addition, the region where the induction lines emerge from the magnets is called magnetic north, and the region in which these induction lines immerse is known as magnetic south.
Magnetic Monopoles
Another characteristic of the magnetic field concerns the non-existence of magnetic monopoles, that is, every magnetic field has a south and a north pole, unlike the electric field, which allows the existence of positive and negative charges, for example.
When some electric charge moves in a region of magnetic field, a magnetic force, perpendicular to the its speed and the direction of the magnetic field, it arises, producing a deflection in the trajectory of the charges electrical devices. This phenomenon often happens in polesmagneticfrom the earth, which have a larger magnetic field and, therefore, are able to deflect charged particles from the solar wind, giving rise to polar auroras.
Do not stop now... There's more after the advertising ;)
magnetic field formula
The formula used to calculate the magnetic field depends on the shape of the body that produces it. The most common cases are those where we calculate the magnetic field of wires, turns and coils. Check out the formulas used to calculate the magnetic field:
Magnetic field of a conductor wire
To calculate the intensity of the magnetic field produced by a conducting wire, crossed by an electric current, we use the following formula:
B – magnetic field (T)
μ0 – magnetic permeability of vacuum (4π.10-7 T.m/A)
i – electric current (A)
d – distance from stitch to thread (m)
The above formula allows us to calculate the strength of a magnetic field, generated by a conducting wire, at a point at a distance d, based on that wire.
Magnetic field generated by a circular loop
The magnetic field generated by a circular loop can be calculated by the following formula:
R – turn radius (m)
Magnetic field generated by a coil
Coils are formed by a set of conducting coils. The calculation of the magnetic field produced by a coil is very similar to that done for the turns, in this case, the difference stays with the integer n — the number of turns that make up the coil:
no – number of turns
Earth's magnetic field
The Earth's magnetic field originates from therotationof the earth's core, which happens at a different speed than the planet's crust. The Earth's core is formed by a large amount of metals that have a large amount of electrical charges, it is the movement of these charges that gives rise to the Earth's magnetic field.
The magnetic field works as a kind of shield for the atmospheric gases, if not for him, the earth atmosphere would be swept away by the large amount of particles that are emitted by the Sun all the time.
The Earth's magnetic field played a important role in navigations, when using the compass as the main navigation tool. In addition, many animals are able to reproduce migratory routes thanks to their ability to sense the orientation of the Earth's magnetic field. If you want to know more about this topic, read our text: Earth's magnetic field.
magnetic field and electric field
Electric and magnetic fields are related, as the English physicist and mathematician showed James Clerk Maxwell (1831-1879). In 1864, Maxwell unified the electrical and magnetic phenomena, showing that light was a wave and that it was produced by the oscillation of electric and magnetic fields.
According to his calculations, Maxwell found that the variation of an electric field gave rise to a magnetic field, just as it was able to produce a dynamic electric field. Maxwell's conclusion was that, together, these vector fields gave rise to the electromagnetic waves, such as visible light, radio waves, X-ray etc.
Read more: Magnetization: How does a material that does not have magnetic characteristics become a magnet?
Solved exercises on magnetic field
(Question 1) A lead wire carries an electrical current of 0.5 A. Determine the strength of the magnetic field produced by this wire, in units of µT (10-6 T), at a point that is 50 cm from this thread.
Data: μ0 = 4π.10-7 T.m/A
a) 20.0 μT
b) 0.2 µT
c) 2.0 µT
d) 4.0 µT
e) 2.5 µT
Template: Letter B
Resolution: Let's use the formula for the magnetic field produced by the wire to calculate what is asked in question 1, here's how:
Through the calculation, we found that the strength of the magnetic field produced by the wire corresponds to the alternative b.
(Question 2) A turn of radius equal to 5 cm is traversed by an electric current of 1.5 A. Determine the strength of the magnetic field produced by this loop.
Data: μ0 = 4π.10-7 T.m/A, use π = 3.
a) 1.5.10-6 T
b) 1.8.10-5 T
c) 2.0.10-4 T
d) 1.3.10-5 T
e) 1.8.10-8 T
Template: Letter B
Resolution: In order to solve the exercise, it is necessary to transform the radius measurement unit to meters (5 cm = 0.05 m), so that we can use the formula of the magnetic field generated by a loop:
Question 3) A 500-turn coil with a radius of 2.5 cm is carried by an electric current of 0.5 A. Determine the strength of the magnetic field, in units of mT (10-3 T), produced by this coil.
Data: μ0 = 4π.10-7 T.m/A, use π = 3.
a) 1.5 mT
b) 2.0 mT
c) 6.0 mT
d) 5.0 mT
e) 3.0 mT
Template: Letter D
Resolution: To solve the exercise, we will use the formula of the magnetic field generated by a coil, note:
At the end of the exercise, it was necessary to shift the position of the comma until the result was expressed in scientific notation.
By M.e Rafael Helerbrock
Physics teacher
