Magnetic Effect Of An Electric Current Pdf

[Brian]

Nucleartheorist Dmitri Kharzeev of Stony Brook University and Brookhaven Lab with Brookhaven Lab materials scientists Qiang Li, Genda Gu, and Tonica Valla in a lab where the team measured the unusual high conductivity of zirconium pentatelluride.

In fact, when physicists in Brookhaven's Condensed Matter Physics & Materials Science Department (CMP&MS) first measured the significant drop in electrical resistance, and the accompanying dramatic increase in conductivity, they were quite surprised. "We didn't know this large magnitude of 'negative magnetoresistance' was possible," said Qiang Li, a physicist and head of the advanced energy materials group in the department and a co-author on a paper describing these results just published in the journal Nature Physics. But after teaming up with Dmitri Kharzeev, the head of the RIKEN-BNL theory group at Brookhaven and a professor at Stony Brook, the scientists had an explanation.

Kharzeev had explored similar behavior of subatomic particles in the magnetic fields created in collisions at the Lab's Relativistic Heavy Ion Collider (RHIC), a DOE Office of Science User Facility where nuclear physicists explore the fundamental building blocks of matter. He suggested that in both the RHIC collisions and zirconium pentatelluride, the separation of charges could be triggered by a chiral imbalance.

"We looked at the data and we said, 'Gee, that's it!' We tested six different samples and confirmed that no matter how you do it, it's there as long as the magnetic field is parallel to the electrical current. That's the smoking gun," Li said.

Right- or left-handed chirality is determined by whether a particle's spin is aligned with or against its direction of motion. In order for chirality to be definitively established, particles have to behave as if they are nearly massless and able to move as such in all three spatial directions.

Some aspects of this phenomenon, namely the linear dependence of the particles' energy on their momentum, can be directly measured and visualized using angle-resolved photoemission spectroscopy (ARPES).

"This chiral imbalance gives a big boost to the separation of the oppositely charged particles, which can be connected through an external circuit," Kharzeev said. And once the chiral state is set it's hard to alter, "so very little energy is lost in this chiral current."

"In a classic generator, the current increases linearly with increasing magnetic field strength, which needs to be changing dynamically. In these materials, current increases much more dramatically in a static magnetic field. You could pull current out of the 'sea' of available quasiparticles continuously. It's a pure quantum behavior," Li said.

"In zirconium pentatelluride and other materials that have since been discovered to have the chiral magnetic effect, an external magnetic field is required to start reducing resistivity," Valla said. "However, we envision that in some magnetic materials, the electrical current could flow with little or no resistance in a direction parallel with the material's internal magnetic field. That would eliminate the need for external magnetic fields and would offer another avenue for dissipationless transport of electrical current."

Kharzeev and Li are also interested in exploring unusual optical properties in chiral materials. "These materials possess collective excitations in the terahertz frequency range, which could be important for wireless communications and also in imaging techniques that could improve the diagnosis of cancer," Kharzeev said.

Getting back to his nuclear physics roots, Kharzeev added, "The existence of massless quasiparticles that strongly interact makes this material quite similar to the quark-gluon plasma created in collisions at RHIC, where nearly massless quarks strongly interact through the exchange of gluons. So this makes Dirac semimetals an interesting arena for testing some of the ideas proposed in nuclear physics."

"This research illustrates a deep connection between two seemingly unrelated fields, and required contributions from an interdisciplinary team of condensed matter and nuclear physicists," said James Misewich, the Associate Laboratory Director for Energy Science at Brookhaven Lab and a professor of physics at Stony Brook University, who played the central role of introducing the members of this research team to one another. "We're fortunate to have scientists with expertise in these fields here at Brookhaven and nearby Stony Brook University, and the kind of collaborative spirit to make such a project come to fruition," he said.

Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Brookhaven National Laboratory is a multipurpose research institution funded by the U.S. Department of Energy. Located on Long Island, NY, Brookhaven operates large-scale facilities for studies in physics, chemistry, biology, medicine, applied science, and advanced technology. The Laboratory's almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.

Brookhaven Science Associates manages and operates Brookhaven National Laboratory on behalf of the U.S. Department of Energy'sOffice of Science. BSA is a partnership between Battelle and The Research Foundation for the State University of New York on behalfof Stony Brook University. More

The magnetic effect of currents is applied in devices like electric motors, generators, transformers, and magnetic resonance imaging (MRI) machines.

The magnetic effect of current, also known as electromagnetism, is a fundamental principle that underpins many modern technologies. One of the most common applications is in electric motors, which are used in a wide range of devices from electric cars to household appliances. In an electric motor, a current is passed through a coil of wire, creating a magnetic field. This interacts with another magnetic field, causing the coil to rotate and drive the motor. Understanding the basics of the magnetic field can provide deeper insights into how these interactions work.

Similarly, generators work on the same principle but in reverse. Instead of using electricity to create motion, they use motion to create electricity. When a coil of wire is rotated in a magnetic field, it induces a current in the wire. This is how most of our electricity is generated, from large-scale power stations to small wind-up torches. The principle of the magnetic field due to a current is essential in understanding how generators function.

Transformers, another application of the magnetic effect of currents, are used to change the voltage of alternating current (AC). They consist of two coils of wire wrapped around a common iron core. When an AC current is applied to one coil, it creates a changing magnetic field in the core, which induces a current in the second coil. By changing the number of turns in each coil, the voltage can be stepped up or down. The process of electromagnetic induction is crucial for the operation of transformers.

Lastly, the magnetic effect of currents is also used in medical imaging. Magnetic Resonance Imaging (MRI) machines use a strong magnetic field to align the protons in the body's hydrogen atoms. A radio frequency current is then applied, causing the protons to spin out of alignment. When the current is turned off, the protons realign and emit a radio signal, which is used to create detailed images of the body's internal structures. This non-invasive technique has revolutionised the field of medical diagnostics. For a deeper understanding of the forces between current-carrying wires in such technologies, exploring forces between current-carrying wires can be enlightening.

IB Physics Tutor Summary: The magnetic effect of currents powers many technologies we use daily. In electric motors, it enables movement in devices from cars to appliances. Generators use this effect to produce electricity, while transformers adjust electrical voltage. In MRI machines, it helps produce detailed body images for medical diagnosis. These applications show the vast impact of electromagnetism in various fields.

A straight current-carrying conductor has a magnetic field in the shape of concentric circles around it. Magnetic field lines can visualise the magnetic field of a straight current-carrying conductor.

Suppose a straight current-carrying conductor is hung vertically, and an electric current is flowing from north to south, i.e. from up to down. In this situation, the direction of the magnetic field will be clockwise. And if the same current is flowing from south to north through the same conductor, the direction of the magnetic field will be anti-clockwise.

Assume that you are holding a straight current-carrying conductor in your right hand such that the thumb points towards the direction of the current. Then your fingers will wrap around the conductor in the direction of the magnetic field lines.

The magnetic field produced in a circular current carrying conductor is the same as that of the magnetic field due to a straight current-carrying conductor and the current-carrying circular loop will behave like a magnet.

The magnetic field lines in a current-carrying circular loop would be in the shape of concentric circles, and at the centre of the circular wire, field lines will become straight and perpendicular to the plane of the coil.

The magnetic field produced by the current-carrying solenoid is similar to a bar magnet. The magnetic field produced inside a solenoid is parallel which is similar to a bar magnet. One solenoid end behaves as a south pole, and the other end behaves as a north pole.

3a8082e126