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Magnetic Force

Magnetic Force

In addition to the electric forces between electric charges, moving electric charges exert magnetic forces on each other. A magnetic field is created by a moving charge or a group of moving charges known as the electric current. A magnetic force is experienced by a second current or moving charge in response to this magnetic field. Fundamentally, interactions between moving electrons in the atoms of two bodies produce magnetic forces between them.
The magnetic force acting on a moving charge...

Magnetism

Magnetism

Magnets are commonly found in everyday objects, such as toys, hangers, elevators, doorbells, and computer devices. Experimentation on these magnets shows that all magnets have two poles: one is labeled north (N) and the other south (S). Magnetic poles repel if they are alike and attract if unlike. Moreover, both poles of a magnet attract unmagnetized pieces of iron.
An individual magnetic pole cannot be isolated. No matter how small, every piece of a magnet contains a north pole and a south...

Magnetic Field Due to Two Straight Wires

Magnetic Field Due to Two Straight Wires

Consider two parallel straight wires carrying a current of 10 A and 20 A in the same direction and separated by a distance of 20 cm. Calculate the magnetic field at a point "P2", midway between the wires. Also, evaluate the magnetic field when the direction of the current is reversed in the second wire.

Magnetic Field Due To A Thin Straight Wire

Magnetic Field Due To A Thin Straight Wire

Consider an infinitely long straight wire carrying a current I. The magnetic field at point P at a distance a from the origin can be calculated using the Biot-Savart law.

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...

Magnetic Force Between Two Parallel Currents

Magnetic Force Between Two Parallel Currents

Two long, straight, and parallel current-carrying conductors exert a force of equal magnitude on one another. The direction of the force depends on the current direction in the conductors.
The force exerted by the magnetic field due to the first conductor over a finite length of the second conductor is given as the product of the current in the second conductor and the vector product of the length vector along the current element and the field due to the first conductor. According to the...

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Related Experiment Video

Updated: Jun 30, 2025

Magnetic Tweezers for the Measurement of Twist and Torque

Magnetic Tweezers for the Measurement of Twist and Torque

Published on: May 19, 2014

Magnetic tweezers principles and promises.

Vincent Croquette¹, Jessica Valle Orero², Martin Rieu³

¹Laboratoire de Physique de l'École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France; ESPCI Paris, Université PSL, Paris, France.

Methods in Enzymology

|March 16, 2024

Summary

Magnetic tweezers enable easy manipulation of single DNA, RNA, or protein molecules. Simple calibration using Brownian motion enhances their utility in biophysics research.

Keywords:

Brownian fluctuations DNA elasticity Magnetic tweezers Micromanipulation Polymer model Single molecule Video tracking

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High-Speed Magnetic Tweezers for Nanomechanical Measurements on Force-Sensitive Elements

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Author Spotlight: Advanced Single-Molecule Techniques for Investigating Telomeric Protein-DNA Interactions

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Related Experiment Videos

Last Updated: Jun 30, 2025

Magnetic Tweezers for the Measurement of Twist and Torque

Magnetic Tweezers for the Measurement of Twist and Torque

Published on: May 19, 2014

High-Speed Magnetic Tweezers for Nanomechanical Measurements on Force-Sensitive Elements

High-Speed Magnetic Tweezers for Nanomechanical Measurements on Force-Sensitive Elements

Published on: May 12, 2023

Author Spotlight: Advanced Single-Molecule Techniques for Investigating Telomeric Protein-DNA Interactions

Author Spotlight: Advanced Single-Molecule Techniques for Investigating Telomeric Protein-DNA Interactions

Published on: August 30, 2024

Area of Science:

Biophysics
Molecular Biology
Biotechnology

Background:

Single-molecule manipulation techniques are crucial for understanding biomolecular mechanics.
Magnetic tweezers offer a powerful, non-invasive method for applying forces to individual molecules.

Purpose of the Study:

To describe a simplified magnetic tweezers setup for routine laboratory use.
To highlight key components and features for optimal experimental focus on biomolecules.

Main Methods:

Utilizing magnetic beads and external magnets to apply controlled forces and torques.
Employing Brownian motion for straightforward calibration of the magnetic tweezers system.

Main Results:

Demonstrated ease of use for manipulating DNA, RNA, and proteins.
Identified factors contributing to the popularity and effectiveness of magnetic tweezers.
Discussed limitations and areas for improvement, particularly regarding torque application.

Conclusions:

The described magnetic tweezers provide a user-friendly platform for single-molecule studies.
Further advancements by the scientific community continue to enhance magnetic tweezers capabilities.