Electric and Magnetic Fields

A field is a mathematical duty that assigns a quantity to each allude in space. Scalar fields assign scalar quantities to each allude in space; vector fields assign vectors to each point in space. In physics, vector areas are supplied to represent the behaviors of forces. Because that example, the behavior of gravitational pressures can be represented by assigning vectors to points in space, where each vector represents the magnitude and also direction that the gravitational pressure that would certainly be exerted on things located at the point.

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Electric and also magnetic forces can also be stood for by vector fields. Every charged thing is surrounding by an electric field. The strength and direction of the electrical field in ~ each allude is defined as the pressure that would certainly be exerted on a bit with 1 coulomb of positive charge if the fragment were situated at that point (whether or no such a fragment is actually located there).

Simulation of an electric Field

Drag a couple of positive and/or an adverse charges (red and blue circles) into the space. Then include electric field sensors (yellow circles) to watch the pressure vectors at any kind of given point. Also try checking the “Electric Field” crate to visualize the electric field lines.


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Images through Geek3, an imaginative Commons patent CC BY-SA 3.0. Click photos for original files. These records have no been modified.

The actions of forces can also be usefully represented using field lines. Field lines room the lines (or curves) through space that monitor the direction of the force vectors at every point. In various other words, they space the courses that would be traced through objects that move in small increments, adhering to the direction the the force vector at one point to a adjacent point (without walking the full length of the vector), then adhering to the direction the the 2nd point’s vector because that a short distance to a third point, and so on. Ar lines execute not show the magnitude (strength) of the pressures at every point, however they do it straightforward to visualize how the directions that the vectors readjust over a an ar of space.

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When an electric present flows follow me a directly wire, magnetic field lines kind concentric circles about the wire.

A magnetic ar is another kind the vector field linked with electrical charges. The direction that the magnetic force vectors in ~ each allude correspond come the direction in which the north pole of a magnet would certainly be moved if the were situated at that point. Magnetic fields are produced whenever a charged thing moves. When a fee object moves in a straight line, the magnetic field lines type concentric circles perpendicular to the object’s direction of travel. Because that example, as soon as an electric existing moves along a straight wire, magnetic field lines type circles roughly the wire. (An electric present is a flow of charged particles, typically electrons.)


Physicists stand for the direction of an electric current as opposite the direction the electron flow. For example, if the electrons are relocating to the right, the electric present is related to as flow to the left.
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When an electric existing travels around a cable loop, magnetic ar lines flow through the loop in one direction. The outflowing next is a magnetic phibìc pole; the inflowing next is a southern pole.

Now imagine what happens if us take that wire and bend it right into a loop so the the current moves in a circle. Magnetic field lines pass v the loop together they encircle every segment that the wire. Every one of these magnetic ar lines flow through the loop in the exact same direction. The an outcome of this arrangement is a magnetic field with 2 magnetic poles: the outflowing side of the loop is dubbed the phibìc pole, and the inflowing side is called the south pole.

Something comparable happens at the microscopic level, as electrons orbit the nucleus of an atom. Together each electron spins roughly the nucleus, the produces a (very weak) magnetic field with north and also south poles. In part atoms, the electrons spin in the opposite directions, so their magnetic areas cancel each other out. However, the magnetic fields created by one atom’s spinning electron don’t constantly cancel out, and many atoms carry out act together miniature magnets. If enough of these atoms are aligned in the very same direction, your magnetic areas work with each other to create a lot stronger magnetic field that can be felt in ~ the macroscopic scale. Magnets room simply products that have actually their atom aligned in this way.

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Magnetic field lines roughly a bar magnetNotice the close same to the electric field lines surrounding a positive and negative charge.
Image by Geek3,Creative Commons license CC BY-SA 3.0. Click photo for original file. This file has not been modified.

Some minerals, favor magnetite, have actually their atoms naturally aligned. Magnets can likewise be artificially created by placing details metals (e.g. Iron) right into a magnetic field, leading to the atom to align (temporarily or permanently, relying on the process) through that magnetic field. Because that example, a straightforward temporary magnet deserve to be made by wrapping wire around a nail, then to run an electric present through the wire. The circling electric charges in the wire create a weak magnetic field, and the iron atom in the pond align with that ar so the their very own magnetic fields work together to develop a lot stronger field. Short-lived magnets like this are called electromagnets. Products that have actually their atom permanently to adjust are called permanent magnets.

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If you break a irreversible magnet in half, each fifty percent will have its own north and also south poles. Repeat this procedure as frequently as girlfriend like; you’ll never get a north pole or a south pole through itself. Because each atom has actually both a north and a southern magnetic pole, that is difficult to acquire a phibìc or southern pole alone. In other words, magnetic “monopoles” don’t exist in nature. And you can’t produce a magnetic monopole in the activities either. Magnetic monopoles simply don’t exist.