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Torque On A Current Loop In A Magnetic Field

Torque On A Current Loop In A Magnetic Field

The most common application of magnetic force on current-carrying wires is in electric motors. These consist of loops of wire, which are placed between the magnets with a magnetic field. When current flows through the loops, the magnetic field applies torque, which causes the shaft to rotate, thus converting electrical energy to mechanical energy.
Consider a rectangular current-carrying loop containing N turns of wire, placed in a uniform magnetic field. The net force on a current-carrying loop...

Force On A Current Loop In A Magnetic Field

Force On A Current Loop In A Magnetic Field

Magnetic forces on wires carrying current are most frequently applied in motors. A DC motor is a device that converts electrical energy into mechanical work. In motors, wire loops are enclosed in a magnetic field. When current flows through the loops, the magnetic field applies torque, which causes the shaft to rotate. The direction of the current is reversed once the loop's surface area is lined up with the magnetic field, causing a constant torque on the loop. During the process, commutators...

Induced Electric Fields: Applications

Induced Electric Fields: Applications

An important distinction exists between the electric field induced by a changing magnetic field and the electrostatic field produced by a fixed charge distribution. Specifically, the induced electric field is nonconservative because it does not work in moving a charge over a closed path. In contrast, the electrostatic field is conservative and does no net work over a closed path. Hence, electric potential can be associated with the electrostatic field but not the induced field. The following...

Faraday's Law

Faraday's Law

Faraday's law state that the induced emf is the negative change in the magnetic flux per unit of time. Any change in the magnetic field or change in the orientation of the area of the coil with respect to the magnetic field induces a voltage (emf). The magnetic flux measures the number of magnetic field lines through a given surface area. Magnetic flux is estimated from the integral of the dot product of the magnetic field vector and the area vector. The negative sign describes the direction in...

Lenz's Law

Lenz's Law

The direction in which the induced emf drives the current around a wire loop can be found through the negative sign. However, it is usually easier to determine this direction with Lenz's law, named in honor of its discoverer, Heinrich Lenz (1804–1865). Lenz's law states that the direction of the induced emf drives the current around a wire loop always to oppose the change in magnetic flux that causes the emf.
If a bar magnet is moved toward a coil such that the magnetic flux through the coil...

Magnetic Force On A Current-Carrying Conductor

Magnetic Force On A Current-Carrying Conductor

Moving charges experience a force in a magnetic field. Since the magnetic fields produced by moving charges are proportional to the current, a conductor carrying a current creates a magnetic field around it.
Consider a compass placed near a current-carrying wire. The wire experiences a force that aligns the needle of the compass tangentially around the wire. Thus, the current-carrying wire produces concentric circular loops of magnetic field. The magnetic field generated by a wire can be...

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Updated: Jul 4, 2026

Magnetic Tweezers for the Measurement of Twist and Torque

Magnetic Tweezers for the Measurement of Twist and Torque

Published on: May 19, 2014

Current-induced torques due to compensated antiferromagnets.

Paul M Haney¹, A H MacDonald

¹Department of Physics, The University of Texas at Austin, Austin, TX 78712-0264, USA.

Physical Review Letters

|June 4, 2008

Summary

Current-induced torques in ferromagnet-antiferromagnet circuits are nonzero due to spin-dependent scattering. This leads to unique phase diagrams for magnetic configurations, differing from ferromagnet-only systems.

Related Experiment Videos

Last Updated: Jul 4, 2026

Magnetic Tweezers for the Measurement of Twist and Torque

Magnetic Tweezers for the Measurement of Twist and Torque

Published on: May 19, 2014

Area of Science:

Condensed matter physics
Spintronics
Materials science

Background:

Current-induced torques are crucial for manipulating magnetization in spintronic devices.
Antiferromagnetic materials offer potential for high-speed and low-power spintronics.

Purpose of the Study:

To investigate the influence of current-induced torques on ferromagnet magnetization in circuits with compensated antiferromagnets.
To determine the form and impact of these torques at the antiferromagnetic interface.

Main Methods:

Analysis of spin-dependent scattering at a compensated antiferromagnetic interface.
Theoretical determination of current-induced torque characteristics.
Comparison of phase diagrams for ferromagnet-antiferromagnet and ferromagnet-only systems.

Main Results:

Current-induced torques are generically nonzero in ferromagnet-antiferromagnet systems.
Symmetry differences in torques lead to distinct phase diagrams.
The magnetic configuration dependence on current and magnetic field is qualitatively altered.

Conclusions:

Compensated antiferromagnets significantly modify current-induced torque effects in magnetic circuits.
The unique torque properties enable novel control of magnetization dynamics.
This research opens avenues for advanced spintronic device design.