oersted experiment magnetic field

Magnetic Field of a Long Straight Wire

Edited by Priya Sharma (Fall 2019)

• 3.1.1 Approximation
• 4.1.1 Application with a Compass
• 5.3 Difficult
• 6 Connectedness
• 7.1 Further Reading
• 7.2 External Links
• 8 References

The magnetic field of a wire was first discovered during an experiment by Hans Christian Oersted (1777-1851) of Denmark in 1820. This experiment consisted of running a current through a wire and placing a compass underneath it to see if there was any effect. The effect he found changed the world forever: he had discovered the important relationship between electricity and magnetism. Before this, the world had taken note of the similarities between electricity and magnetism but nobody had truly "proved" this relationship up until this point. Oersted then went on to write his groundbreaking scientific paper "Experiments on the effect of a current of electricity on the magnetic needle," which shocked and awed the rest of the scientific world. This was the birth of Physics 2. If it had not been for Oersted, we might not be taking this very class at Georgia Tech! While this finding falls directly into the category of "Magnetic Field of a Long Straight Wire," it also may very well be the most important discovery by any physicist in history (this is up for debate but this is just my opinion on the topic; nonetheless, it is extremely crucial).

A long straight wire, that is carrying some current I, will generate it's own magnetic field. The shape of the magnetic field will be concentric circles centered around the wire. The magnetic field lines are identical and the spacing of these lines increases as the distance increased. The direction of the magnetic field lines can be observed by placing small compass needles on a circle close to the wire. If there is no current, then the needles will align with the Earth's magnetic field and if there is a current, then the needles will point tangent to the circle. If the wire is vertical and the current is facing upwards, then on the left side of the wire, the magnetic field will come out towards you. On the right side of the wire, the magnetic field would go in towards the other direction. If the current was going downwards, then the magnetic field would reverse directions but would still be in concentric circles around the wire. The second form of the right hand rule in terms of the wire would be used so that the thumb is going in the direction of the current, and the fingers will go in the direction of the magnetic field. The closer you get to the wire, the stronger the magnetic field. The further you get from the wire, the weaker the magnetic field. As the magnetic field gets spread out, it is distributed over a wider circumference. The mathematical interpretation of the magnetic field is detailed below.

Mathematical Model

Imagine centering a wire of length [math]\displaystyle{ L }[/math] on the y-axis, and having a current [math]\displaystyle{ I }[/math] run through the wire in the +y direction. We are interested in finding the magnetic field at some point along the z axis, say [math]\displaystyle{ (0,0,z) }[/math] .

From here, we use the Biot-Savart Law:

In our case, [math]\displaystyle{ \mathbf{\hat r} }[/math] is simply a unit vector in the direction of a point along the wire [math]\displaystyle{ (0,y,0) }[/math] to a point along the z-axis [math]\displaystyle{ (0,0,z) }[/math] . This can be represented by:

In our case, [math]\displaystyle{ d\mathbf{L} }[/math] is simply a vector pointing along a length of the wire. Since our wire is solely along the y-axis, this can be reduced as follows:

Now we can compute the absolute value of the cross product between [math]\displaystyle{ \mathbf{\hat r} }[/math] and [math]\displaystyle{ d\mathbf{L} }[/math] , where [math]\displaystyle{ r = \sqrt{y^2 + z^2} }[/math] :

Thus we have:

To find the total magnetic field at a point along the z-axis due to the wire, we integrate from one end of the wire to the other end of the wire, or in this case:

The integral then is:

Therefore, the total magnetic field [math]\displaystyle{ B }[/math] due to a wire of length [math]\displaystyle{ L }[/math] with current [math]\displaystyle{ I }[/math] at a distance [math]\displaystyle{ z }[/math] away from the wire is:

Approximation

If it is known that [math]\displaystyle{ L \gt \gt z }[/math] , then the denominator of the above formula can be approximated by:

Therefore, if you have a really long wire, and you are trying to find the magnetic field of a point relatively close to the rod, you can use the approximation:

In most situations, at least in the scope of this course, it is stated in the question whether or not you can use the approximation. This can come in a few different forms: "assume z<<L," "assume the length of the wire is much longer than than the distance from the wire to the observation location," etc. However, if it is not explicitly stated, a good rule of thumb is that if the length of the wire is 100 times+ the [math]\displaystyle{ z }[/math] , we can use the approximation formula. Otherwise, it is smart to just play it safe and use the full formula.

Magnetic Field Near a Midpoint of the Wire

Computational model.

This can be found in the mathematical model section where the infinitesimal piece is integrated. This can also be done in Glowscript as shown below:

Application with a Compass

If you run a current through a wire and place a compass near it, the needle of the compass deflects due to the magnetic field from this wire. With no current in the wire, the compass will face North. When approximately .314A is run through a wire, the compass deflects by approximately 20 degrees. In fact, the amount of deflection that there is from the wire can actually help you calculate the approximate magnetic field of the wire. This is because there is a particular relationship between the needle of the compass, the magnetic field of the wire, and the magnetic field of the Earth itself that looks like this:

The Earth itself has a magnetic field anywhere on the Earth (based on location it varies slightly, but it is easier to assume it is constant) of approximately [math]\displaystyle{ 2e^{-5} \ \text{T} }[/math] which is why the compass points notes. In the formula above, theta is the amount of degrees that, when placed directly above or underneath, the compass needle deflects from North. This is a very useful formula to have in lab or in the real world if it is unknown how much current is running through a wire.

The magnitude of the magnetic field [math]\displaystyle{ 50 \ \text{cm} }[/math] from a long, thin, straight wire is [math]\displaystyle{ 8.0 \ \text{μT} }[/math] .

The current through a thin, straight wire that is [math]\displaystyle{ 2 \ \text{m} }[/math] long is [math]\displaystyle{ 74 \ \text{A} }[/math] .

There are two wires, separated by a distance of [math]\displaystyle{ 80 }[/math] meters on the x-axis. The left wire has a current running through it of [math]\displaystyle{ 5 \ \text{A} }[/math] , while the right wire has a current running through it of [math]\displaystyle{ 12 \ \text{A} }[/math] . The length of the left wire is [math]\displaystyle{ 2 }[/math] meters, while the length of the right wire is [math]\displaystyle{ 3 }[/math] meters.

Connectedness

I am very interested in clean energy storage and production, which typically involves long wires at some point between where the energy is generated and where the electricity is used. It is important to understand all the forces involved with an electrical current, so that if something goes wrong, you can determine where the problem is and why it might be occurring so that you can fix it.

I am an Electrical Engineering major, so all of the material within this class is vastly important, not only for the following courses required for an EE major, but also for the field once we graduate and find a job. However, this concept specifically interests me because for a while I had a very difficult time finding the direction of the magnetic field in situations such as these, so this is my way of giving back in an effort to make sure future students don't run into the same problem.

I am an Industrial Engineering major and think that it is really interesting to see the theory behind how compasses are affected by currents within a wire and their associated magnetism. A compass is such an everyday item but I had never looked into why it works the way it does, and this specific topic gave me a lot of insight into that. Additionally, it is really intriguing to learn about the second form of the right hand rule and its applications.

Further Reading

• HyperPhysics Biot-Savart Law
• Bozeman Science Magnetic Field of a Wire

External Links

• Magnetic Field of a Loop
• Magnetic Field of a Disk
• Biot-Savart Law for Currents
• Magnetic Field
• Moving Point Charge
• Matter and Interactions Vol. II
• OpenStax University Physics
• Skulls in the Stars

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Oersted's experiment, what it shows:.

Oersted showed that an electric current produces a magnetic field. His experiment is repeated here on a suitable grand scale.

How it works:

f igure 1. Compass platform and dimensions of wire loop

Setting it up:

The current loop can be clamped upright onto a lecture bench; the base rests on the ground. Current is supplied by a Sorensen 1 DC supply at 250A (the ends of the tube are fitted with high current connectors). The compass needles are 15cm in length. 2

The current should be increased gradually to 250A to limit compass oscillations. Hans Christian Oersted (1777-1851) was the first to find a connection between electricity and magnetism. His demo could be used as one of the stepping stones towards Maxwell's equations. The experiment is repeated on a smaller scale in OHP Magnetic Lines of Force .

1 Sorensen (Raytheon) DCR20-250 power supply 2 Sergent-Welch 1869

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July 1820: Oersted & Electromagnetism

By the end of the 18th century, scientists had noticed many electrical phenomena and many magnetic phenomena, but most believed that these were distinct forces. Then in July 1820, Danish natural philosopher Hans Christian Oersted published a pamphlet that showed clearly that they were in fact closely related.

Hans Christian Oersted was born in August 1777, in Rudkobing, Denmark. He was educated mainly at home, and showed some interest in science as a child. At age 13 he apprenticed himself to his father, a pharmacist. In 1794, he entered the University of Copenhagen, where he studied physics, philosophy and pharmacy, and earned a PhD in philosophy.

He completed his PhD in 1801, and, as was customary, he began traveling around Europe, visiting Germany and France and meeting other scientists. One person he met, and may have been inspired by, was Johann Ritter, one of the few scientists at the time who believed there was a connection between electricity and magnetism.

Returning to Copenhagen in 1803, Oersted sought a university position teaching physics, but didn’t immediately get one. Instead he began giving lectures privately, charging admission. Soon his lectures became popular, and he was given an appointment in 1806 at the University of Copenhagen, where he expanded the physics and chemistry program and established new laboratories. He also continued his own research in physics and other areas of science. His first scientific paper was on electrical and chemical forces. He investigated a variety of problems in physics, including the compressibility of water and the use of electric currents to explode mines.

Oersted made the discovery for which he is famous in 1820. At the time, although most scientists thought electricity and magnetism were not related, there were some reasons to think there might be a connection. For instance, it had long been known that a compass, when struck by lightning, could reverse polarity. Oersted had previously noted a similarity between thermal radiation and light, though he did not determine that both are electromagnetic waves. He seems to have believed that electricity and magnetism were forces radiated by all substances, and these forces might somehow interfere with each other.

During a lecture demonstration, on April 21, 1820, while setting up his apparatus, Oersted noticed that when he turned on an electric current by connecting the wire to both ends of the battery, a compass needle held nearby deflected away from magnetic north, where it normally pointed. The compass needle moved only slightly, so slightly that the audience didn’t even notice. But it was clear to Oersted that something significant was happening.

Some people have suggested that this was a totally accidental discovery, but accounts differ on whether the demonstration was designed to look for a connection between electricity and magnetism, or was intended to demonstrate something else entirely. Certainly Oersted was well prepared to observe such an effect, with the compass needle and the battery (or “galvanic apparatus,” as he called it) on hand.

Whether completely accidental or at least somewhat expected, Oersted was intrigued by his observation. He didn’t immediately find a mathematical explanation, but he thought it over for the next three months, and then continued to experiment, until he was quite certain that an electric current could produce a magnetic field (which he called an “electric conflict”).

On July 21, 1820, Oersted published his results in a pamphlet, which was circulated privately to physicists and scientific societies. His results were mainly qualitative, but the effect was clear – an electric current generates a magnetic force.

His battery, a voltaic pile using 20 copper rectangles, probably produced an emf of about 15-20 volts. He tried various types of wires, and still found the compass needle deflected. When he reversed the current, he found the needle deflected in the opposite direction. He experimented with various orientations of the needle and wire. He also noticed that the effect couldn't be shielded by placing wood or glass between the compass and the electric current.

The publication caused an immediate sensation, and raised Oersted’s status as a scientist. Others began investigating the newly found connection between electricity and magnetism. French physicist André Ampère developed a mathematical law to describe the magnetic forces between current carrying wires. Starting about a decade after Oersted’s discovery, Michael Faraday demonstrated essentially the opposite of what Oersted had found – that a changing magnetic field induces an electric current. Following Faraday’s work, James Clerk Maxwell developed Maxwell’s equations, formally unifying electricity and magnetism.

Oersted continued working in physics. He started the Society for Dissemination of Natural Science, which was dedicated to making science accessible to the public, something he thought was very important. In 1829 he established the Polytechnical Institute in Copenhagen. He was also a published writer and poet, and contributed to other fields of science, such as chemistry – for instance, in 1825 he produced aluminum for the first time. Oersted died in 1851. His 1820 discovery marked the beginning of a revolution in the understanding of electromagnetism, providing the first connection between what had been thought to be two very different physical phenomena.

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Your Physicist

I will answer anything from the world of physics.

Oersted’s experiment

Oersted’s experiment: a brief overview.

In 1820, Danish physicist Hans Christian Oersted conducted a groundbreaking experiment that demonstrated the connection between electricity and magnetism. Oersted’s experiment involved passing an electric current through a wire, which caused a nearby compass needle to deflect. This observation led him to conclude that an electric current produces a magnetic field.

The Discovery of Electromagnetism

Oersted’s discovery of electromagnetism paved the way for further research into the relationship between electricity and magnetism. It inspired other scientists, such as Michael Faraday and James Clerk Maxwell, to conduct experiments that ultimately led to the development of electromagnetic theory. Electromagnetic theory is a fundamental concept in physics that explains how electric and magnetic fields are interrelated and how they propagate through space.

How Oersted’s Experiment Changed Science

Oersted’s experiment revolutionized the field of physics and had a significant impact on the development of modern technology. It led to the invention of electric motors, generators, and other electrical devices that have transformed industries such as transportation, telecommunications, and manufacturing. The discovery of electromagnetism also paved the way for the development of many other scientific fields, such as electronics, nanotechnology, and quantum mechanics.

Example Applications of Electromagnetism Today

Today, electromagnetism is used in a wide range of applications, from medical imaging to electric power generation. Magnetic resonance imaging (MRI) is a medical imaging technique that uses strong magnetic fields to generate images of the body’s internal structures. Electromagnetic waves are also used in telecommunications, including radio, television, and satellite communication. Electric power generation is another application of electromagnetism, with generators using magnetic fields to produce electricity. Additionally, electromagnetism plays a crucial role in the operation of electric motors and generators, which are used in a variety of industrial processes. Overall, Oersted’s experiment laid the foundation for the development of many modern technologies and continues to shape our understanding of the natural world.

The National MagLab is funded by the National Science Foundation and the State of Florida.

Ørsted's Compass

In 1820, Hans Christian Ørsted discovered the relationship between electricity and magnetism in this very simple experiment.

In 1820, Hans Christian Ørsted stumbled upon a discovery that birthed the study of electromagnetism. While setting up materials for a lecture, Ørsted happened to bring a compass close to a live electrical wire. He noticed that the needle of the compass jumped when close to the wire. After more experimentation and documentation, he officially proved that magnetic fields are created when current travels through a wire, thus proving that electricity and magnetism are connected.

Play with the tutorial below to experience the phenomenon as Ørsted did.

Instructions

• Identify all the parts of Ørsted’s setup and take note of the direction the compass needle is pointing.
• Close the circuit by pushing the “on” button.
• Observe what happens to the compass needle when electricity is flowing through the wire.
• Flip the battery, and watch the compass needed change direction.
• Turn the system off. Watch the needle move back to pointing North when there is no longer current running through the wire.

The battery Ørsted used was a voltaic pile, which is made of copper and zinc plates in an acid solution. A metal wire is connected to the battery and held up by wooden clamps. A compass is placed below the wire. The compass needle points north until the circuit is connected because it is reacting to the earth’s magnetic field. When the system is turned on, the magnetic field of the wire overpowers the force of the earth’s magnetic field on the needle. When the battery is flipped, the direction of the current is reversed and so is the way the needle is pointing.

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Home > Alternating Current > Oersted’s Law of a Magnetic Field of a Straight Current Carrying Conductor

Oersted’s Law of a Magnetic Field of a Straight Current Carrying Conductor

Oersted’s law of electromagnetism – its formula and applications, what is oersted’s law.

A Danish physicist Hans Christian Ørsted discovered the relation between electricity and magnetism on 21 April 1820 known as Oersted’s law which states that “ Electric current creates a magnetic field surrounding it “.

The Oersted experiment has a strong influence on Joseph Henry and Michael Faraday and after exploring the magnetic effect of current in a deeper sense which led them to lay the foundation of the modern electrical machinery.

After many experiments, Oersted found that a straight current carrying conductor induces a magnetic field where the direction of magnetic field depends on the direction of flowing current in the conductor. The direction of the magnetic field can be found by the right hand thumb rule or Fleming’s left & right hand rules .

In simple words, Oersted found the following points for a straight current carrying conductor.

• A current carrying conductor creates a magnetic field around it.
• The magnetic field lines of force (created by current) encircle the current carrying conductor.
• The magnetic field lines of force (created by current) lie in a plane perpendicular to the conductor (i.e. at right angle (90°) to each other).
• The change in the direction of flow of current will also change the direction of magnetic field lines of force.
• The magnetic field strength is directly proportional to the current density.
• The magnetic field strength at a point is inversely proportional to the distance of that point from the current carrying wire.
• The magnetic field exists around the wire until the flow of current is abandoned.

Ørsted’s magnetic compass experiment (which detected that straight electric current creates a straight magnetic field) confirms the following facts as well.

• If two parallel current carrying conductors have the same current but opposite in direction, the resultant magnetic field will be zero. This is because both magnetic fields have opposite polarities and repel each other.
• If two parallel current carrying conductors have the same current and direction, the resultant magnetic field will be doubled. This is because both magnetic fields have the same polarity and attract each other.
• The magnetic effect is directly proportional to the flowing current in the conductor.

Good to know: The equation of Ørsted’s Law only applicable to Direct Current (DC) circuits with no inductors and capacitors . In other words, it fails in an Alternating Current (AC) circuit consisting of a battery charging a capacitor through a resistor . 

Formula and Equation of Oersted’s law

Oersted’s law can be described in the vector form as follows.

∮ C B d l = μ o I

∮ C B d l = μ o ∫∫ s J . dS

• B = Magnetic Field
• I = Current
• ∮ C = Line integral around a closed curve
• J = Current density
• S = Surface
• Absolute permeability = μ o  = 4 π ×10 -7 H/m

Applications of Oersted’s law

As listed as one of the Maxwell’ Equation (Ampere-Maxwell equation or Maxwell-Faraday equation), Oersted experiments laid the foundation of advance electrical machinery systems such as:

• Electric Motors.
• Electric Transformers.
• Electric Generators and alternators.
• Headphones, microphones and tap record players.
• Magnetometers and musical instruments such as electric guitar etc.
• Digital Microcontrollers and Microprocessors .

Related Posts:

• What is Faraday’s Law? Laws of Electromagnetic Induction
• Coulomb’s Laws of Magnetic Force – Formula & Solved Example
• What is Coulomb’s Law? Laws of Electrostatics With Example
• Lenz’s Law of Electromagnetic Induction
• Kirchhoff’s Current & Voltage Law (KCL & KVL) | Solved Example
• Ohm’s Law with Simple Explanation
• What is Joule’s Law and Heating Effect of Current

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Oersted’s Experiment

Activity length, electricity, activity type, exploration.

Students explore the relationship between electricity and magnetism. 

In 1820, a Danish physicist, Hans Christian Oersted, discovered that there was a relationship between electricity and magnetism. By setting up a compass through a wire carrying an electric current, Oersted showed that moving electrons can create a magnetic field.

The magnetic field created by the current goes in circles around the wire.

Students explore the relationship between electricity and magnetism.

Per Student: Pocket compass One-foot (30 cm) length of fairly thick wire, insulated or bare. 1.5 volt electric cell (“battery”) of size “D” or “C” Sheet of paper

Key Questions

• What happens to the compass when the wire is connected to the battery?
• What happens to the compass when you change the direction of the electric current?
• How does the compass needle move when the compass is below the wire? Above the wire?

• Lay the compass on a table, face upwards. Wait until it points north.
• Lay the middle of the wire above the compass needle, also in the north-south direction. You may lightly tape the wire to the table so that it stays put.
• Connect one end of the wire to each end of the battery. Observe the compass. Did the needle move?
• Quickly disconnect the wire from the battery. (It is not good for the battery to draw such a large current). What happens to the needle when you disconnect the wire?
• Repeat with the connections of the battery reversed. In what direction does the needle move this time?
• Take a piece of paper (5×10 cm) and fold the longer side into pleats (like a little accordion), about 1 cm high. Put the wire on the table, its middle in the North-South direction, put the pleated paper above it so that the wire is below one of the pleats, and place the compass on top of the pleats.
• You can now repeat the experiment with the compass above the wire. What direction does the compass move in this time?

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oersted , unit of magnetic-field strength in the centimetre-gram-second system of physical units. Named for the 19th-century Danish physicist Hans Christian Ørsted , it is defined as the intensity of a magnetic field in a vacuum in which a unit magnetic pole (one that repels a similar pole at a distance of one centimetre with a force of one dyne ) experiences a mechanical force of one dyne in the direction of the field .

Physics Lens

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Oersted’s Experiment

Hans Christian Oersted showed that an electric current can affect a compass needle in 1820. This confirms the direct relationship between electricity and magnetism, which in turn, paved the way for further understanding of the two. The direction of the magnetic field can be changed by flipping the wire around, which suggests that the direction of the magnetic field is dependent on the direction of current flow.

• 1.5V Battery
• Place the compass on a horizontal surface.
• Connect the wire to both ends of the battery.
• Place the middle of the wire directly over the compass, parallel to the initial orientation of the needle.
• Observe the needle deflect to one direction.
• Now flip the wire over so the current flows in the opposite direction and place it over the compass again.
• The needle will deflect in the other direction.
• Additionally, you can place the compass on top of the wire now.

Science Explained

A current will carry with it its own magnetic field. The magnetic field lines form concentric circles around the wire so that the field points in one direction above the wire and the opposite direction below the wire. Using the right-hand grip rule, where one holds his hands as though he is gripping something with his thumb pointing in the direction of current flow, his fingers will curl in a way as to indicate the direction of the magnetic field. This is also the direction in which the needle deflects.

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Science project, oersted's experiment.

Hans Christian Oersted was a Danish scientist who explored the relationship between electric current and magnetism. Current is the flow of electrons, and is how we hardness electricity. Currents create their own magnetic fields in closed loops, which magnets are known to induce , or create current, in wires.

Oersted experimented with this, using a compass, which uses the magnetic poles of the Earth to show your which direction you are facing. By bringing the compass near a closed current loop, he was able to interfere with the magnetic field and cause the compass needle to move.

Observe electromagnetic induction by recreating Oersted’s Experiment.

What will happen when you bring the compass towards the current loop?

• Insulated wire
• Electrical tape
• Electical tape
• Cut a 1 meter loop of insulated wire.
• Use electrical tape to secure a stripped end of the wire to one side of a D battery.
• Run the wire up one side of the box, across the top, and down the other side. Make sure you have enough wire so that it can run along the table or ground to reconnect the battery. Now you have a loop!
• Connect the other open end of the wire to the battery so current begins to flow.
• Bring the compass into the center of the loop. What happens?
• Move the compass around closer to the wire and away from the wire. Record your observations.

The wire will carry a current that creates a magnetic field around itself. Bringing the compass near the wire or in the loop will cause the compass needle to move.

The current will induce a magnetic field based on the right-hand rule. Make a “thumbs-up” sign with your right hand. The thumb will be the direction of the current (flowing from the negative to positive terminal of the battery) and the fingers will curve around in the direction of the magnetic field.

The magnetic field created by the current will interfere with the magnetic field the compass experiences when it is brought near enough.

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Question about oersted's experiment

So I was studying my physics notes. They are on the magnetic field shown by a straight current carrying wire. To demonstrate that theres the oersted's experiment. The starting goes like this-

Insert a thick copper wire between 2 points, X and Y, in a circuit. The wire should be perpendicular to the plane of paper . Place a compass horizontally to the wire. Switch on the current. The compass needle shows deflection

My question is - what does placing the wire XY perpendicular to the plane of paper mean?

And why would you do that? Please help.

• electromagnetism

• $\begingroup$ Why do you think it should be otherwise? $\endgroup$ –  user36790 Commented Oct 2, 2016 at 6:29
• $\begingroup$ first of all, I don't even understand what paper we are talking about. If you have studied this experiment then can you please explain me which paper we are talking about? $\endgroup$ –  MartianCactus Commented Oct 2, 2016 at 6:44

2 Answers 2

“The paper” is probably just meaning the table. So let's put the wire vertically going in the up-down direction. Using the right-hand-rule we obtain that the magnetic field will be circles in the plane of the table/paper.

The compass will align itself to the magnetic field lines. Therefore the rotating compass should be positioned such that it points towards the wire or parallel to it. When you turn on the magnetic field, it can align itself with the magnetic field lines.

Take a look at some video of the experiment. There you can see that the magnet will align itself perpendicular to the wire and parallel to the plane that the wire is perpendicular to (that sentence is probably unnecessarily complex).

• $\begingroup$ and my teacher also told me something like, the force is more when you align the magnetic field perpendicular to the direction of electric current flow $\endgroup$ –  MartianCactus Commented Oct 4, 2016 at 6:33

It means you poke the wire through the paper. If you were to shake some iron filings on to the paper they'd line up along the magnetic field lines like little compass needles. The magnetic field lines can be drawn like this:

By the way, despite what you might be told by people who can't answer your questions, there are people who understand magnetism and how it works. Don't listen to people who tell you physics can't supply the answers. It can. That's why we do physics. We do physics to understand the world, not to make predictions. Don't forget that Maxwell wrote On Physical Lines of Force . The force is real, and so are those iron filings and the pretty patterns:

Whilst there are no "lines of force" per se in the space around the wire, they do map out something real - a magnetic field. Electromagnetic field interactions result in linear and rotational forces. A uniform magnetic field is a place where the linear forces cancel, but the rotational forces do not. Hence when you throw an electron through the middle of a solenoid, it follows a helical path. Note though that a typical magnetic field is not uniform, and so we see linear forces too. Hence two wires like the above attract one another. But if you reverse the current in one of the wires, they repel.

• $\begingroup$ so, if we don't place the wire perpendicular...will the force be less? $\endgroup$ –  MartianCactus Commented Oct 10, 2016 at 6:30
• $\begingroup$ Not really, because it's only perpendicular to your piece of paper. The force on a charged particle depends on how you throw it. Check out hyperphysics . I think it's a great website. $\endgroup$ –  John Duffield Commented Oct 10, 2016 at 7:18
• $\begingroup$ oh ok thanks for the answer!! Also, about the physics answers "why" thing...there are somethings taught in school that when I learn I have a LOT of doubts about..but all these doubts are out-of-course and I understand the basic concept of what is being taught. Will these doubts clear as I go to collage and stuff? $\endgroup$ –  MartianCactus Commented Oct 10, 2016 at 8:17
• $\begingroup$ I'm sure a lot will. But not all of them. And to be honest, that's a good thing. That's what drives scientists into searching for better understanding. $\endgroup$ –  John Duffield Commented Oct 10, 2016 at 18:11

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