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Bobină Helmholtz – Wikipedia
It consists of two electromagnets on the same axis. Most Helmholtz coils use DC direct current to produce a static magnetic field. The capacitance is chosen to resonate the coil at the desired frequency. In other projects Wikimedia Commons.
If the radius is Rthe number of turns in each coil is n and the current through the coils is Ithen the magnetic field B at the midpoint between the coils will be given by.
These applications include magnetic field susceptibility tests, scientific experiments, and biomedical studies the interaction between magnetic field and living tissue. Substituting nI for I in the above formula gives the field for an n -turn coil:.
Helmholtz coil – Wikipedia
Each coil carries an equal electric current in the same direction. This page was last edited on 16 Decemberat To improve the uniformity of the field in the space inside the coils, additional coils can heljholtz added around the outside.
The waveform amplifier driver must be able to output high AC current to produce the magnetic field. Views Read Edit View history.
This is sometimes called a Maxwell coil. Webarchive template wayback links Commons category link is on Wikidata. Use the above equation in the mathematics section to calculate the coil current for a desired magnetic field, B. Retrieved from ” https: The calculation of the exact magnetic field at any point in space is mathematically complex and involves the study of Bessel functions. Generating a static magnetic field is relatively easy; the strength of the field is proportional to the current.
Besides creating magnetic fields, Helmholtz coils are also used in scientific apparatus to cancel external magnetic fields, such as the Earth’s magnetic field.
Instead of directly driving the coil with a high voltage, a series resonant circuit may be used to provide the high voltage. By symmetry, the odd-order terms in the expansion are zero.
From symmetry, the field strength at the midpoint will be twice the single coil value:. The required magnetic fields are usually either pulse or continuous sinewave. The calculation detailed below gives the exact value of the magnetic field at the center point.
From Wikipedia, the free encyclopedia. Then calculate the required Helmholtz coil driver amplifier voltage: Electromagnetic coils Magnetic devices Hermann von Helmholtz.
In some applications, a Helmholtz coil is used to cancel out the Earth’s magnetic fieldproducing a region with a magnetic field intensity much closer to zero. Only the coils parasitic resistance remains. The coils are inductors, and their impedance increases proportionally with frequency.
The Helmholtz coils consists of n turns of wire, so the equivalent current in a one-turn coil is n times the current I in the n -turn coil. An AC Helmholtz coil driver is needed to generate the required time-varying magnetic field. Wikimedia Commons has media related to Helmholtz coils. Generating a high-frequency magnetic field is more challenging. Many applications and experiments require a time-varying magnetic field.
Start bobie the formula for the on-axis field due to a single wire loop which is itself derived from the Biot—Savart law: This method only works at frequencies close to the resonant frequency; to generate the field at other frequencies requires different capacitors.
To provide the same field intensity at twice the frequency requires twice the voltage across the coil. A Helmholtz coil is a device for producing a region of nearly uniform magnetic fieldnamed after the German physicist Hermann von Helmholtz.