section 12.1 magnetic fieldssph4u1 sec8.1 magnetism.notebook 1 december 04, 2020 jan 3 9:48 pm...
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Section 12.1 Magnetic Fields
A magnetic field is the threedimensional region of space surrounding a magnet that will exert a force on magnetic objects. The magnetic field exists around the magnet whether the magnetic field is causing a force or not.
Earth has a magnetic field that exists both inside and surrounding it. Other types of fields also exist in nature. A gravitational field exists around Earth because of Earth’s mass, and it causes objects with mass to be attracted toward Earth’s centre. Electric fields surround charged particles such as protons and electrons. The electric fields cause charged particles to experience forces of attraction or repulsion.
What is a FIELD?
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Oersted's Discovery
Is there a link between electricity and magnetism?
Charged particles behave in a similar way to magnetic poles. Like charges (positive and positive or negative and negative) repel each other and unlike charges (positive and negative) attract each other.
In 1819, Danish physicist Hans Christian Oersted was the first scientist to successfully connect electricity and magnetism. We have since found out that the electromagnetic force is one of the four fundamental forces of nature.
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Oersted discovered that a wire with current running through it creates a magnetic field around the wire. The field can be "seen" by using a magnetic compass. The arrow on the compass will seek out magnetic North when there is no current present, but with current present the arrow follows the magnetic field created by the electric current in the wire.
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Oersted’s principle whenever a charge moves through a straight conductor, a circular magnetic field is created around the conductor.
He also noted, that when the current direction changed, so did the direction of the compass arrow.
In Oersted's time, the conventional current model, positive to negative flow, was the norm; hence his principle has two versions (conventional and electron flow).
Link
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Right Hand Rule Magnetic Fields Conventional Flow Model
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Left Hand Rule Magnetic Fields Electron Flow Model
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Representing Currents and Magnetic Fields in a Wire Visual Aids for the Conventional Current Model
Note the red tip of the arrow gives direction of the field.
N N
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Putting Magnetic Fields to Good Use Solenoid
Two magnetic fields can interact with each other to cause a force. The force can either be attractive or repulsive, depending on the directions of the two interacting fields. If two field lines point in the same direction, a repulsion force is applied. Conversely, if two field lines point in opposite directions, an attractive force is applied.
magnetic field lines point in the same direction repulsive force
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Coiled Conductors Building Upon a Simple IdeaRemember, we are using the Conventional Flow (pos to neg) approach.
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An electromagnet is a device that has a magnetic field produced by an electric current. The benefit of the electromagnet is that it can be switched on and off . The strength of the electromagnet can be increased by increasing the number of loops in the coil, increasing the current, or introducing a core made from a material that is quickly magnetized. Soft iron is such a material, and it can be just as quickly demagnetized when the current is switched off . A core material like soft iron concentrates the magnetic field. To make a very powerful magnet, we include all three factors. The most powerful electromagnets have several thousand loops of wire, work with large currents, and have a soft iron core.
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There are only four elements in the world that are ferromagnetic at room temperature and can become permanently magnetized: iron, nickel, cobalt and gadolinium. (A fifth element, dysprosium, becomes ferromagnetic at low temperatures.)
In ferromagnetic materials, smaller groups of atoms band together into areas called domains, in which all the electrons have the same magnetic orientation. That's why you can magnetize them. See how it works in this tutorial.Electrons are teeny tiny magnets. They have a north and a south pole, too, and spin around an axis. This spinning results in a very tiny but extremely significant magnetic field. Every electron has one of two possible orientations for its axis.In most materials, atoms are arranged in such a way that the magnetic orientation of one electron cancels out the orientation of another. Iron and other ferromagnetic substances, though, are different (ferrummeans iron in Latin). Their atomic makeup is such that smaller groups of atoms band together into areas called domains, in which all the electrons have the same magnetic orientation. .
Electrons and Domains
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Homework
Read 386 87 Domain Theory
Read 390 "Using.."
page 391 #1, 2, 7
Solenoid
Mag Field Wire
Magnet links