PHYSIK LABOR: Spezifische Ladung des Elektrons e/m - Teil 1: Magnetfeld eines Helmholtz-Spulenpaares

Further videos on the Physics 2 lab experiments: 1. Preparation and execution of the Franck-Hertz experiment:    • PHYSIK LABOR: Vorbereitung und Durchführun...   2a. Specific charge of the electron e/m - Part 1: Magnetic field of a Helmholtz coil pair:    • PHYSIK LABOR: Spezifische Ladung des Elekt...   2b. Specific charge of the electron e/m - Part 2: Theory and sources of error:    • PHYSIK LABOR: Spezifische Ladung des Elekt...   2c. Specific charge of the electron e/m - Part 3: Experimental procedure and measurements:    • PHYSIK LABOR: Spezifische Ladung des Elekt...   3. Michelson interferometer: in preparation 4. Diffraction at a single/double slit/grating: in preparation 5. Determination of the Faraday constant: in preparation Further videos on the Physics 1 lab experiments: Experiment 1 (Free fall and projectile motion 1/2):    • PHYSIK LABOR - Kinematik, Freier Fall und ...   Experiment 1 (Free fall and projectile motion 2/2):    • PHYSIK LABOR - Kinematik, Freier Fall und ...   Experiment 2 (Handheld measuring instruments / Error calculation):    • PHYSIK LABOR - Handmessmittel / Fehlerrech...   Experiment 3 (Dampened oscillations / Pohl's wheel):    • PHYSIK LABOR - Erzwungene, gedämpfte Schwi...   Experiment 4 (Central Collision):    • PHYSIK LABOR - Zentraler Stoß (elastisch/u...   Physics problems related to the Biot-Savart Law: Magnetic Field / Biot-Savart - Problem 5 - Magnetic Field Strength of a Closed Conductor Circuit:    • PHYSIK AUFGABEN (Induktion, Magnetismus) -...   Magnetic Field / Biot-Savart - Problem 6 - Electron in an Evacuated Tube:    • PHYSIK AUFGABEN (Induktion, Magnetismus) -...   Magnetic Field / Biot-Savart - Problem 7 - Radioactive Decay of 146Sm:    • PHYSIK AUFGABEN (Induktion, Magnetismus) -...   ---------------------------------------------------------------------------------------------------------------------------------------------------------- Regarding the current video: This first video deals with the calculation of the magnetic Magnetic field of a ring conductor or two ring conductors – also known as Helmholtz coils. In summary, this video discusses the magnetic properties of a Helmholtz coil pair for providing a homogeneous magnetic field for the laboratory experiment to determine the specific charge of the electron (e/m), in order to make a statement about the influence of field inhomogeneities. Using the Biot-Savart law, a formula is first derived for calculating the axial component along the axis of symmetry. Additionally, I show how the magnetic field components can also be calculated at any point using elliptic integrals. This allows the flux density in the radial direction to be calculated for interesting planes, e.g., the plane parallel to the coils midway between them or in the plane of the coils themselves. Finally, I include a 3D field simulation with ANSYS, which confirms the analytical results. The second film then deals with the experiment itself (theory and practice), including the measurement of the magnetic flux density. Helmholtz Coils The Helmholtz coil is named after the German physicist Hermann von Helmholtz. It consists of two identical magnetic coils arranged parallel to each other, with their centers lying on the same axis. The two coils are separated by a distance equal to the coil radius. Normally, the two coils are connected in series, so that the same current supplies both coils and generates two identical magnetic fields. The two combined Helmholtz fields produce a very uniform magnetic field in a cylindrical volume located midway between the two coils. This region with a uniform field (cylindrical shape) is approximately 25% of the coil radius (R) wide and 50% of the distance between the two coils long. Helmholtz coils are typically used for scientific experiments, magnetic calibration, or, for example, to cancel out the Earth's background magnetic field. How is a magnetic field created? A magnetic field is always created when a charge is in motion, i.e., either moving in space or rotating on its axis. A charge moving in space is called a "current" (represented by the symbol I) and is measured in coulombs per second or amperes. The strength of the magnetic field is measured at a point in space (often called a field point). In the case of Helmholtz coils, the field points of interest are located in the median plane between the two coils. As can be seen from the corresponding equation B_z = μ_0*I*R²/(2*sqrt(R²+z²)³) the strength of the magnetic field depends on three quantities: 1. the current I, 2. the number of turns n in each coil, and 3. the radius R of the coil. The total current in each coil is n*I. Technical data of the calculated coils used in the experiment: Coil diameter: 300 mm Number of turns: 124 per coil Coil resistance: 1.2 ohms Max. current per coil: 5 A Max. flux density (5 A): 3.7 mT