Name: current and magnetic field around a wire
Uploaded: 2023-04-30T12:40:55.000Z
Duration: 1 min 25 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Physical Science

motion-and-stability-forces-and-interactions

Motion and Stability- Forces and Interactions

PS.PSc.6.4

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

Magnetic Force On A Current-Carrying Conductor

Prendiamo ad esempio una bussola posizionata vicino a un conduttore che trasporta corrente. L'ago subisce una forza ed è allineato tangenzialmente a un cerchio attorno al conduttore. Pertanto, attorno al conduttore si formano anelli concentrici di campi magnetici.
La direzione del campo magnetico generato dal conduttore può essere determinata dalla regola della mano destra: il pollice punta nella direzione della corrente e le dita avvolte forniscono la direzione.
Se il campo magnetico si muove verso l'esterno dal piano, è rappresentato da un punto; se si muove verso il piano, è rappresentato da una croce.
Si consideri una sezione infinitesimale del conduttore che trasporta corrente in un campo magnetico uniforme. Se n è la densità numerica delle tariffe gratuite, è possibile determinare il numero di portatori di carica nella sezione.
Ricordando l'equazione della velocità di deriva, è possibile determinare la forza magnetica su una singola carica e la forza magnetica totale nella sezione.
Supponendo che la lunghezza della sezione infinitesimale sia nella stessa direzione della velocità di deriva, è possibile determinare la forza sul conduttore che trasporta corrente.

<ol>
	<li>OpenStax. (2019). Fisica universitaria Vol. 2. [Versione web], Pg 396 - 398. Estratto da <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>

forza magnetica in un conduttore attraversato dalla corrente

Le cariche in movimento sperimentano una forza in un campo magnetico. Poiché i campi magnetici prodotti dalle cariche in movimento sono proporzionali alla corrente, un conduttore che trasporta corrente crea un campo magnetico attorno a sé.

Consideriamo una bussola posta vicino a un filo conduttore che trasporta corrente. Il filo sperimenta una forza che allinea l'ago della bussola tangenzialmente intorno al filo. Quindi, il filo conduttore che trasporta corrente produce anelli concentrici di campo magnetico. Il campo magnetico generato da un filo può essere determinato utilizzando la regola della mano destra, secondo la quale se il pollice punta nella direzione della corrente, allora la direzione in cui le dita si avvolgono intorno al filo indica la direzione del campo magnetico prodotto. Consideriamo un piano rettangolare nella direzione XY. Se il campo magnetico esce dal piano, quelle linee di campo magnetico sono rappresentate da un simbolo a punto. Se il campo magnetico entra nel piano, quelle linee di campo magnetico sono rappresentate da un simbolo a croce.

Consideriamo un filo conduttore rettilineo con corrente che scorre dal basso verso l'alto che ha una lunghezza 1 e un'area trasversale A. Il filo conduttore è posto in un campo magnetico uniforme che è perpendicolare al piano e diretto verso il piano. La velocità di deriva agisce verso l'alto e è perpendicolare al campo magnetico. La forza media su ogni carica è diretta a sinistra e è data come segue:

<img alt="Equation1" src="/files/ftp_upload/13768/13768_Equation_1.svg" style="text-align: center; height: 22px;" />

Se ci sono n cariche per unità di volume, allora l'area trasversale del filo moltiplicata per il numero di cariche per unità di volume e la lunghezza dà il volume del filo segmentato. Pertanto, la forza magnetica totale sul segmento ha una magnitudine come segue:

<img alt="Equation2" src="/files/ftp_upload/13768/13768_Equation_2.svg" style="text-align: center; height: 14px;" />

Ricordando l'equazione della velocità di deriva e sostituendo i termini, la forza totale sul segmento può essere calcolata come segue:

<img alt="Equation3" src="/files/ftp_upload/13768/13768_Equation_3.svg" style="text-align: center; height: 12px;" />

Forza magnetica in un conduttore attraversato dalla corrente

Le cariche in movimento subiscono una forza in un campo magnetico. Poiché i campi magnetici prodotti dalle cariche in movimento sono proporzionali alla corrente, un conduttore ...

Education

Didattica

JoVE Core

Physics

Fisica

Unit 1

Unità 1

Magnetic Forces and Fields

Forze e Campi Magnetici

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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

Magnetic Force on Moving Charges

Magnetic force on moving charges depends on motion, charge, and field direction. A moving charge or a current creates a magnetic field in the space around it, along with its electric field. That magnetic field can then push on other moving charges or currents in the field. A magnetic field is a vector field, so it has direction as well as strength. At any point, the field direction is the direction a compass needle’s north pole points. The field strength is defined from the force a charged...

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

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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JoVE Core Physics introduces the theory and application of fundamental physics topics, including kinematics, dynamics, fluid mechanics, statics, waves, and acoustics, with concise and easy-to-understand animated videos. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

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Ohio’s Learning Standards and Model Curriculum

Electricity And Magnetism

Electromagnetic interactions

Tennessee Academic Standards

High School

Energy

PHYS.PS3.9

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HIgh School

PS.9

PS.9.d

PH.7

PH.7.a

PH.7.b

Minnesota Academic Standards in Science

3.1.1 9P.2.2.1.3

Alabama Course of Study Science

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Waves and Their Applications in Technologies for Information Transfer

9-12.PS.2.3.b

Florida Department of Education

SC.912.P.10

SC.912.P.10.10

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New York State Science Learning Standards

HS. Forces and Interactions

HS-PS2-5.

HS. Energy

HS-PS3-5.

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 ...

Average Velocity

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Instantaneous Velocity - I

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Instantaneous Velocity - II

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Average Acceleration

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Instantaneous Acceleration

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Position and Displacement Vectors

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average-and-instantaneous-velocity-vectors

Average and Instantaneous Velocity Vectors

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Acceleration Vectors

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Force and Momentum

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

PS.PSc.4.1

Electrical Current

Electrical current is defined as the rate at which charge flows. When there is a large current present, such as that used to run a refrigerator, a large ...

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

Many materials exhibit a simple relationship between the values of current, voltage, and resistance, known as Ohm&#8217;s law. The current that flows ...

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.

PS.PSc.6.2

Continuity Equation

The total amount of current flowing per unit cross-sectional area is called the current density. Hence, the current passing through a cross-sectional area ...

Boundary Conditions for Current Density

Current density becomes discontinuous across an interface of materials with different electrical conductivities. The normal component of the current ...

Electrical Conductivity

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Theory of Metallic Conduction

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Obtain, evaluate, and communicate information to explain how current is affected by changes in composition, length, temperature, and diameter of wire.

PS.PSc.6.3

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Magnetic Fields

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Magnetic Field Lines

The representation of magnetic fields by magnetic field lines is very useful in visualizing the strength and direction of the magnetic field. Each of the ...

Magnetic Flux

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Motion Of A Charged Particle In A Magnetic Field

A charged particle experiences a force when moving through a magnetic field. Consider the field to be uniform and the charged particle to move ...

Magnetic Force

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Moving charges experience a force in a magnetic field. Since the magnetic fields produced by moving charges are proportional to the current, a conductor ...

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Force On A Current Loop In A Magnetic Field

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Torque On A Current Loop In A Magnetic Field

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The Hall Effect

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Consider a point charge moving with a ...

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Magnetic Field Due to Two Straight Wires

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magnetic-force-between-two-parallel-currents

Magnetic Force Between Two Parallel Currents

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Magnetic Field Of A Current Loop

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Divergence and Curl of Magnetic Field

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To evaluate the divergence of the ...

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A fundamental property of a static magnetic field is that it is not conservative, unlike an electrostatic field. Instead, there is a relationship between ...

Ampere's Law: Problem-Solving

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Magnetic Field of a Solenoid

A solenoid is a conducting wire coated with an insulating material, wound tightly in the form of a helical coil. The magnetic field due to a solenoid is ...

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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