Name: balancing weight with magnetic force
Uploaded: 2025-05-22T09:05:51.000Z
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K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Physical Science

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Motion and Stability- Forces and Interactions

PS.PSc.6.4

magnetic-force-on-current-carrying-wires-example

Magnetic Force On Current-Carrying Wires: Example

Considérons un conducteur dans le plan XY transportant le courant vers la gauche. Le conducteur se compose de deux segments droits d’une longueur de L parallèle à l’axe des x et d’un demi-cercle de rayon de R.
Si le conducteur est placé dans un champ magnétique uniforme perpendiculaire au plan du fil, pointant vers l’extérieur, déterminez la force magnétique totale sur le conducteur.
Tout d’abord, déterminez la force magnétique pour les différentes sections droites transportant le courant dans la direction x.
Deuxièmement, divisez le segment incurvé en sections droites infinitésimales ayant une longueur de dl à un angle de thêta.
La longueur infinitésimale et le champ magnétique sont perpendiculaires l’un à l’autre, et la direction de leur produit vectoriel est radialement vers l’extérieur. Ainsi, l’amplitude et les composantes de la force sur les sections peuvent être déterminées.
En intégrant l’expression par rapport à thêta, la force sur l’ensemble du conducteur courbe peut être déterminée.
Enfin, en additionnant les forces sur les trois sections, on peut obtenir la force totale sur le conducteur dans la direction y positive.

<ol>
	<li>OpenStax. (2019). Physique universitaire Vol. 2. [Version Web], p. 396 à 398. Tiré de <a href="https://openstax.org/books/university-physics-volume-2@8ede2ba/pages/11-4-magnetic-force-on-a-current-carrying-conductor">https://openstax.org/books/university-physics-volume-2@8ede2ba/pages/11-4-magnetic-force-on-a-current-carrying-conductor</a></li>
</ol>

force magnétique sur des fils porteurs de courant : exemple

Dans un champ magnétique, les charges en mouvement rencontrent une force. Si un fil contient ces charges en mouvement, c'est-à-dire si le fil transporte un courant, alors une force agit également sur le fil. Considérons une paire de fils flexibles maintenant un fil de 40 cm de longueur et d'un poids de 10 g dans une position horizontale. Le fil est placé dans un champ magnétique constant de 0,40 T, comme indiqué dans la Figure 1(a). Déterminez l'intensité et la direction du courant circulant dans le fil nécessaire pour éliminer la tension dans les fils de support.

Pour résoudre le problème, dessinez d'abord un schéma du système, comme le montre la Figure 1(b). Utilisez ensuite la règle de la main droite pour déterminer la direction de la force magnétique agissant sur le fil. Enfin, égalisez les deux forces pour déterminer le courant circulant dans le fil.

<img alt="Equation1" src="/files/ftp_upload/13769/13769_Figure_1.png" style="text-align: center;" />

Dans un schéma du système, la tension dans les fils de support est nulle lorsque les forces magnétique et gravitationnelle sont équilibrées. En utilisant la règle de la main droite, la force magnétique pointe vers le haut, et en égalisant les deux forces de poids et de force magnétique sur le fil :

<img alt="Equation2" src="/files/ftp_upload/13769/13769_Equation_2.svg" style="text-align: center; height: 20px;" />

<img alt="Equation3" src="/files/ftp_upload/13769/13769_Equation_3.svg" style="text-align: center; height: 50px;" />

L'intensité du courant dans le fil peut être déterminée. Le champ magnétique important crée une force significative sur une longueur de fil pour contrebalancer le poids du fil.

Force magnétique sur des fils porteurs de courant : Exemple

Dans un champ magnétique, les charges en mouvement rencontrent une force. Si un fil contient ces charges mobiles, c’est-à-dire si le fil transporte un courant, alors une force agit ...

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Unit 1

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Magnetic Forces and Fields

Forces et champs magnétiques

KEY TERMS AND CONCEPTS

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balancing weight with magnetic force

Magnetic force can balance the weight of a current-carrying wire when the wire sits in a magnetic field. Moving charges in the wire feel a force, so the wire itself can be pushed upward or downward. This example uses a flexible wire that is 40 cm long and has a mass of 10 g. It is held in a horizontal position inside a constant 0.40 T magnetic field.

The goal is to find the current needed to remove the tension in the supporting leads. To do that, a free-body diagram is drawn first. The diagram shows the forces acting on the wire. Then the right-hand rule is used to find the direction of the magnetic force on the wire.

When the tension in the leads is zero, the magnetic force and the gravitational force are balanced. The magnetic force points up, so it can counter the wire’s weight. By setting the weight equal to the magnetic force, the current in the wire can be determined. The strong magnetic field produces a large enough force on the wire to support its weight.

Balancing Weight with Magnetic Force

magnetism

Magnetic Poles and Everyday Uses

Magnetism appears in many everyday objects, from toys and hangers to elevators, doorbells, and computer devices. Magnets have two poles, called north and south. Like poles repel each other, while unlike poles attract. Both poles can also attract unmagnetized iron. A single magnetic pole cannot be isolated, because every part of a magnet contains both a north pole and a south pole. A compass needle is a simple example of a magnet. It is a thin bar magnet suspended at its center, so it can turn...

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Magnetic Force on Moving Charges

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magnetic field lines

Reading Magnetic Field Lines

Magnetic field lines show the direction and strength of a magnetic field. They make it easier to picture how a magnet acts in space. Each line forms a closed loop around the magnet. For a bar magnet, the field lines leave the north pole and curve around to the south pole. They then continue through the magnet back to the north pole. This loop has no beginning or end. Magnetic field lines follow clear rules. The magnetic field points tangent to a field line at any point. A small compass points...

magnetic flux

Magnetic Flux Through Surfaces

Magnetic flux through a surface describes how much magnetic field passes across that surface. It is measured in weber (Wb), the SI unit for magnetic flux. Magnetic flux is a scalar quantity, not a vector. Three factors shape magnetic flux. They are the magnetic field strength B, the area the field crosses, and the orientation of the field relative to the surface. For a small area element dA, the flux depends on the part of the magnetic field that is normal, or perpendicular, to that element at...

motion of a charged particle in a magnetic field

motion-of-a-charged-particle-in-a-magnetic-field

Charged Particle Paths in Magnetic Fields

A charged particle in a magnetic field follows a path that depends on the direction of its velocity. When the field is uniform and the particle moves perpendicular to it, the magnetic field is the main factor that controls the motion, especially in a vacuum. The magnetic force is always perpendicular to the direction of motion, so the particle curves into a circle. Because the force stays perpendicular to velocity, it does no work on the particle. The kinetic energy and speed stay constant...

magnetic force

Magnetic Fields and Moving Charges

Magnetic fields and moving charges create magnetic force. A moving electric charge, or a current made of many moving charges, produces a magnetic field. When another current or moving charge enters that field, it feels a magnetic force in response. At the atomic level, magnetic forces come from interactions between moving electrons in the atoms of two bodies. The strength of magnetic force depends on several factors. It increases with the size of the charge and with the strength of the...

magnetic force on a current-carrying conductor

magnetic-force-on-a-current-carrying-conductor

Current and Magnetic Field Around a Wire

A current-carrying wire creates a magnetic field around it, and moving charges feel a force in that field. Because the magnetic field produced by moving charges is proportional to current, the wire itself acts as a source of magnetic field. A compass placed near the wire shows this effect by lining up tangentially around the wire. The magnetic field around a straight wire forms concentric circular loops. The right-hand rule helps determine the direction of those loops. If the thumb points in...

magnetic force on current-carrying wires: example

Magnetic force can balance the weight of a current-carrying wire when the wire sits in a magnetic field. Moving charges in the wire feel a force, so the wire itself can be pushed upward or downward. This example uses a flexible wire that is 40 cm long and has a mass of 10 g. It is held in a horizontal position inside a constant 0.40 T magnetic field. The goal is to find the current needed to remove the tension in the supporting leads. To do that, a free-body diagram is drawn first. The diagram...

force on a current loop in a magnetic field

force-on-a-current-loop-in-a-magnetic-field

Current Loops and Torque in Motors

Current loops in a magnetic field create the torque that drives a DC motor. A DC motor converts electrical energy into mechanical work. In a motor, wire loops sit inside a magnetic field. When current flows through the loops, the magnetic field pushes on them and makes the shaft rotate. The current is reversed when the loop lines up with the magnetic field. This keeps the torque on the loop going in the same direction. A commutator and brushes handle this reversal. The commutator switches the...

torque on a current loop in a magnetic field

torque-on-a-current-loop-in-a-magnetic-field

Current Loop Torque in Electric Motors

Current loop torque in electric motors shows how magnetic force can make a wire loop rotate. In an electric motor, loops of wire sit between magnets in a magnetic field. When current flows through the loops, the field applies torque. This rotation turns a shaft and converts electrical energy into mechanical energy. A rectangular current-carrying loop with N turns in a uniform magnetic field has zero net force. Even so, it can still experience net torque. The torque depends on the current I,...

the hall effect

Hall Voltage and Charge Carriers

Hall voltage and charge carriers are explained through Edwin H. Hall’s 1879 experiment. His setup helped identify the polarity of the main charge carriers in a conducting material. It also showed, for the first time, that the charge carriers in most metals are negative. A metal slab is placed in a constant magnetic field. The electrons move from right to left, so the magnetic force pushes them toward the top edge of the slab. This leaves excess negative charge at the top and excess positive...

thomson's e/m experiment

Electron Speed Selector in Thomson’s Tube

A velocity selector uses electric and magnetic fields to choose charged particles with one speed from a beam. Many beams from a heated cathode contain particles moving at different speeds, so this setup helps produce a uniform beam. The electric and magnetic fields are perpendicular to the particle’s motion and to each other. In this arrangement, a particle with charge q, speed v, and mass m enters from the top. The magnetic field points into the plane of the paper, and the electric field...

key terms and concepts

Find out how a current-carrying wire can be supported by a magnetic field. Use a free-body diagram and the right-hand rule to solve for current.

Balancing Weight with Magnetic Force | JoVE K12

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Ohio’s Learning Standards and Model Curriculum

Electricity And Magnetism

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Waves and Their Applications in Technologies for Information Transfer

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Balancing Weight with Magnetic Force

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