Examples of magnetic domain in the following topics:
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- Regions within the material (called domains) act like small bar magnets.
- Within domains, the poles of individual atoms are aligned.
- In response to an external magnetic field, the domains may grow to millimeter size, aligning themselves.
- (b) When magnetized by an external field, the domains show greater alignment, and some grow at the expense of others.
- Individual atoms are aligned within domains; each atom acts like a tiny bar magnet.
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- Within domains, the poles of individual atoms are aligned, and each atom acts like a tiny bar magnet.
- In an unmagnetized ferromagnetic object, domains are small and randomly oriented.
- In response to an external magnetic field, the domains may grow to millimeter size, aligning themselves as shown in part (b) of the second figure.
- (b) When magnetized by an external field, the domains show greater alignment, and some grow at the expense of others.
- Individual atoms are aligned within domains; each atom acts like a tiny bar magnet.
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- Permanent magnets are objects made from ferromagnetic material that produce a persistent magnetic field.
- Recall that a magnet is a material or object that generates a magnetic field.
- A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field .
- Ferromagnetic materials can be divided into magnetically "soft" materials like annealed iron, which can be magnetized but do not tend to stay magnetized, and magnetically "hard" materials, which do.
- An example of a permanent magnet: a "horseshoe magnet" made of alnico, an iron alloy.
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- Paramagnetism is the attraction of material while in a magnetic field, and diamagnetism is the repulsion of magnetic fields.
- Paramagnetism is a form of magnetism whereby the paramagnetic material is only attracted when in the presence of an externally applied magnetic field.
- Paramagnetic materials have a relative magnetic permeability greater or equal to unity (i.e., a positive magnetic susceptibility) and hence are attracted to magnetic fields.
- Unlike ferromagnets, paramagnets do not retain any magnetization in the absence of an externally applied magnetic field, because thermal motion randomizes the spin orientations responsible for magnetism.
- Diamagnetism is the property of an object or material that causes it to create a magnetic field in opposition to an externally applied magnetic field.
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- Magnetic field lines are useful for visually representing the strength and direction of the magnetic field.
- Since magnetic forces act at a distance, we define a magnetic field to represent magnetic forces.
- If magnetic monopoles existed, then magnetic field lines would begin and end on them.
- (A) The magnetic field of a circular current loop is similar to that of a bar magnet.
- Relate the strength of the magnetic field with the density of the magnetic field lines
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- When an electrical wire is exposed to a magnet, the current in that wire will experience a force—the result of a magnet field.
- When an electrical wire is exposed to a magnet, the current in that wire will be affected by a magnetic field.
- The expression for magnetic force on current can be found by summing the magnetic force on each of the many individual charges that comprise the current.
- In this instance, θ represents the angle between the magnetic field and the wire (magnetic force is typically calculated as a cross product).
- Express equation used to calculate the magnetic force for an electrical wire exposed to a magnetic field
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- This changing magnetic flux produces an EMF which then drives a current.
- When a conductor carries a current, a magnetic field surrounding the conductor is produced.
- The resulting magnetic flux is proportional to the current.
- From Eq. 1, the energy stored in the magnetic field created by the solenoid is:
- Energy is "stored" in the magnetic field.
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- Helical motion results when the velocity vector is not perpendicular to the magnetic field vector.
- In this case, the magnetic force is also perpendicular to the velocity (and the magnetic field vector, of course) at any given moment resulting in circular motion.
- What if the velocity is not perpendicular to the magnetic field?
- shows how electrons not moving perpendicular to magnetic field lines follow the field lines.
- (Recall that the Earth's north magnetic pole is really a south pole in terms of a bar magnet. )
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- The magnetic force on a charged particle q moving in a magnetic field B with a velocity v (at angle θ to B) is $F=qvBsin(\theta )$.
- How does one magnet attracts another?
- Magnetic fields exert forces on moving charges, and so they exert forces on other magnets, all of which have moving charges.
- The magnitude of the magnetic force $F$ on a charge $q$ moving at a speed $v$ in a magnetic field of strength $B$ is given by:
- This formula is used to define the magnetic strength $B$ in terms of the force on a charged particle moving in a magnetic field.
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- Solenoids are loops of wire around a metallic core, and can be used to create controlled magnetic fields.
- Early in the 19th century, it was discovered that electrical currents cause magnetic effects.
- Electromagnetism is the use of electric current to make magnets.
- These temporarily induced magnets are called electromagnets.
- An electromagnet creates magnetism with an electric current.