We modify a standard Freshman physics experiment with the aim to produce high density plots of two-dimensional electric potentials versus position. To achieve this we connect a voltage probe to a rotary motion sensor and a computer interface so that it becomes possible to sample and record the potential at high rates through horizontal and vertical transects of the conductive paper. We perform some data filtering, and then illustrate the method with the electric dipole.
In this note we synthesize and extend expressions for the magnetic field at the center of very short and very long current-carrying coils. Elementary physics textbooks present the following equation for the magnetic field inside a very long current-carrying coil (solenoid): Bsol=μ0NLI,(1) where I is the current, N the number of windings, and L the coil length. It is obtained directly from Ampère's law, ignores end effects (hence it assumes an infinite coil), and is valid over the entire cross-section of the coil. The field is in the axial direction and it follows the right-hand rule convention. For N superposed loops of radius R each carrying current I, the multi-loop magnetic field at the center is given by Bml=μ0N2RI.(2)
Efficient and accurate nondestructive inspection systems that save time can benefit scheduled maintenance of aircraft structures. Portable nondestructive inspection techniques capable of scanning larger area structures could find great utility and save considerable time and labor. Contemporary fixed location nondestructive inspection systems, such as the gold standard water-coupled ultrasound imaging by the “squirter” require structural disassembly of the part to be inspected and transportation to/from dedicated location. For large aircraft structures, such as vertical or horizontal stabilizers, this adds weeks to the off-site nondestructive inspection process. An on-site ultrasound detecting method for larger areas, comprising a flexible transducer panel of embedded fiber optic Bragg gratings that is lightweight and portable, and reusable over different structures, is described here. It is shown that this fiber Bragg grating embedded ultrasound transducer panel and readout hardware–software system can map tiny surface displacements of guided wave ultrasound, onsite, over an area of approximately 2 square feet in just over 10 min. The test sample is a sandwich structure with composite skins on both sides of an aluminum metal honeycomb section of an aircraft vertical stabilizer with an artificial engineered disbond. The ultrasound propagation data acquired at 612 positions over the large area, enables in situ nondestructive inspection of defects/ damage by comparing post-damage data with baseline data, and is independent of the material information.
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