"Helmholtz coil" is composed of the basic conditions of its composition:
If there is a pair of the same current-carrying circular coil parallel to each other and **** axis, with the same direction of the current, when the coil spacing is equal to the radius of the coil, the two current-carrying coils of the total magnetic field in the axis of the mid-point of the near the larger range is uniform. Therefore, in the production and scientific research has a greater practical value, but also commonly used in weak magnetic field measurement standard.
Magnetic field distribution is characterized by: in the internal generation of high uniformity of the magnetic field, the general uniformity of the long solenoid is better than the Helmholtz coils, but for both can be added to compensate for the coil to get a high degree of uniformity.
Because the Helmholtz coil has an open nature, it is easy to put other instruments or remove, but also can be done directly visual observation, so, is often used in physical experiments device. Named for the German physicist Hermann von Helmholtz.
Extended information:
The Helmholtz coil consists of a pair of identical circular coils of conductors. Using a right-angled coordinate system, the center axes of both of these circular coils of radius R are coaxial with the z-axis.
Calculations of the exact magnetic field at an arbitrary position in space require the application of the Besseau function or elliptic function with its associated tricks. Along the center axis of the coil (z-axis), the calculations involved are simpler, and a Taylor expansion can be applied to expand the magnetic field as a power series of z. A right-angled coordinate system is used, with the center of the Helmholtz coil at the origin of the z-axis O. Due to symmetry with respect to the xy-plane, the odd power term must equal zero.
Industrial frequency magnetic field is characterized by low frequency, long wavelength, its test waveform for the industrial frequency sinusoidal wave, can be a variety of electrical and electronic equipment to varying degrees. For example, a type of equipment such as electric meter may produce program disorder, memory data loss and meter error and other malfunctions under the action of industrial frequency magnetic field.
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