Name: current and magnetic field around a wire
Uploaded: 2023-04-30T12:40:55.000Z
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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-a-current-carrying-conductor

Magnetic Force On A Current-Carrying Conductor

Considérons une boussole placée près d’un conducteur porteur de courant. L’aiguille subit une force et est alignée tangentiellement à un cercle autour du conducteur. Ainsi, des boucles concentriques de champs magnétiques se forment autour du conducteur.
La direction du champ magnétique généré par le conducteur peut être déterminée par la règle de la main droite : le pouce pointe dans la direction du courant et les doigts enroulés fournissent la direction.
Si le champ magnétique se déplace vers l’extérieur du plan, il est représenté par un point ; s’il se déplace vers le plan, il est représenté par une croix.
Considérons une section infinitésimale du conducteur porteur de courant dans un champ magnétique uniforme. Si n est la densité numérique des charges gratuites, le nombre de porteurs de charge dans la section peut être déterminé.
En rappelant l’équation de la vitesse de dérive, la force magnétique sur une seule charge et la force magnétique totale dans la section peuvent être déterminées.
En supposant que la longueur de la section infinitésimale est dans la même direction que la vitesse de dérive, la force sur le conducteur porteur de courant peut être déterminée.

<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 un conducteur porteur de courant

Les charges en mouvement subissent une force dans un champ magnétique. Étant donné que les champs magnétiques produits par les charges en mouvement sont proportionnels au courant, un conducteur porteur de courant crée un champ magnétique autour de lui.

Considérons une boussole placée près d'un fil porteur de courant. Le fil subit une force qui aligne l'aiguille de la boussole de manière tangentielle autour du fil. Ainsi, le fil porteur de courant produit des boucles concentriques de champ magnétique. Le champ magnétique généré par un fil peut être déterminé en utilisant la règle de la main droite, qui stipule que si le pouce pointe dans la direction du courant, alors la direction dans laquelle les doigts s'enroulent autour du fil donne la direction du champ magnétique produit. Considérons un plan rectangulaire dans la direction XY. Si le champ magnétique sort du plan, ces lignes de champ magnétique sont représentées par un symbole de point. Si le champ magnétique entre dans le plan, ces lignes de champ magnétique sont représentées par un symbole de croix.

Considérons un fil conducteur rectiligne avec un courant circulant du bas vers le haut qui a une longueur l et une aire de section transversale A. Le fil conducteur est placé dans un champ magnétique uniforme qui est perpendiculaire au plan et dirigé vers le plan. La vitesse de dérive agit vers le haut et est perpendiculaire au champ magnétique. La force moyenne sur chaque charge est dirigée vers la gauche et est donnée comme suit :

<img alt="Equation1" src="/files/ftp_upload/13768/13768_Equation_1.svg" style="text-align: center; height: 22px;" />

Si n charges par unité de volume sont présentes, alors l'aire de section transversale du fil multipliée par le nombre de charges par unité de volume et la longueur donnent le volume du fil segmenté. Ainsi, la force magnétique totale sur le segment a une magnitude comme suit :

<img alt="Equation2" src="/files/ftp_upload/13768/13768_Equation_2.svg" style="text-align: center; height: 14px;" />

En rappelant l'équation de la vitesse de dérive et en substituant les termes, la force totale sur le segment peut être calculée comme suit :

<img alt="Equation3" src="/files/ftp_upload/13768/13768_Equation_3.svg" style="text-align: center; height: 12px;" />

Force magnétique sur un conducteur porteur de courant

Les charges en mouvement subissent une force dans un champ magnétique. Étant donné que les champs magnétiques produits par les charges en mouvement sont proportionnels au courant, un conducteur ...

Education

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Physics

Physique

Unit 1

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Magnetic Forces and Fields

Forces et champs magnétiques

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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 the direction of the current, the curled fingers show the direction of the magnetic field around the wire.

Magnetic field lines are also shown with symbols in a plane. A dot symbol means the field points out of the plane, while a cross symbol means the field points into the plane. For a straight conducting wire with current flowing upward, the wire can be placed in a uniform magnetic field directed into the plane.

In that setup, the drift velocity points upward and stays perpendicular to the magnetic field. The average force on each charge points to the left. If the wire segment has length l and cross-sectional area A, then the volume of the segment is found from A times the length, and the total magnetic force on the segment can be written from that charge count. Using the drift velocity equation lets the force be rewritten in a final form.

Current and Magnetic Field Around a Wire

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...

magnetic fields

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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

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magnetic force on a current-carrying conductor

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-on-current-carrying-wires-example

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...

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

See how a current-carrying wire creates circular magnetic field lines, how the right-hand rule shows field direction, and how force acts on moving charges.

Current and Magnetic Field Around a Wire | JoVE K12

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Waves and Their Applications in Technologies for Information Transfer

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SC.912.P.10.10

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New York State Science Learning Standards

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HS-PS2-5.

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Position and Displacement

The position of an object defines its location relative to a convenient frame of reference at any particular time. A frame of reference is an arbitrary ...

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Instantaneous Velocity - I

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Instantaneous Velocity - II

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Analyze and interpret data to explain the motion of an object moving with a constant velocity or that is accelerating.

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Drift Velocity

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Current Density

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Resistivity

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Resistance

When a current moves through any conductor, the conductor causes some level of difficulty for the current to flow. The measure of that difficulty is known ...

Ohm's Law

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Non-ohmic Devices

In most substances, the current flow is proportional to the voltage applied to it. A simple relationship between the values of current, voltage, and ...

Construct an explanation to compare simple series and parallel circuits in terms of Ohm's Law.

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Continuity Equation

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Boundary Conditions for Current Density

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Magnetic Field Lines

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Magnetic Flux

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Torque On A Current Loop In A Magnetic Field

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magnetic-force-between-two-parallel-currents

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Magnetic Field of a Solenoid

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Use models to explain magnetism in terms of domains, interactions of poles, and magnetic fields.

Analyze motion in terms of speed, velocity, acceleration, and momentum.

Current and Magnetic Field Around a Wire

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