Magnetism & Electromagnetism - The Power of Attraction (Magnets) Robins can literally see magnetic fields, but only if their vision is sharp | Not Exactly Rocket Science. Some birds can sense the Earth’s magnetic field and orientate themselves with the ease of a compass needle. This ability is a massive boon for migrating birds, keeping frequent flyers on the straight and narrow. But this incredible sense is closely tied to a more mundane one – vision. Thanks to special molecules in their retinas, birds like the European robins can literally see magnetic fields. The fields appear as patterns of light and shade, or even colour, superimposed onto what they normally see. Katrin Stapput from Goethe University has shown that this ‘magnetoreception’ ability depends on a clear image from the right eye. The magnetic sense of birds was first discovered in robins in 1968, and its details have been teased out ever since. When cryptochrome is struck by blue light, it shifts into an active state where it has an unpaired electron – these particles normally waltz in pairs but here, they dance solo.
Reference: Current Biology. The Solenoid and the Toroid. Toroid is a hollow circular ring (like a medu vadai) on which a large number of turns of a wire are wound. The above figure represents a toroid wound with a wire carrying a current I. Consider path 1, by symmetry , if there is any field at all in this region, it will be tangent to the path at all point and will equal the product will equal the product of B and the circumference d = 2pr of the path.
The current through the path however is zero and hence from Ampere's law the field B must be zero. Similarly, if there is any field at path 3, it will also be tangent to the path at all points. The field of the toroidal solenoid is therefore confined wholly to the space enclosed by the windings. If we consider path 2, a circle of radius r, again by symmetry the field is tangent to the path and Each turn of the winding passes once through the area bounded by path 2 and total current through the area is NI, where N is the total number of turns in the windings. Using Ampere's law = 0). Magnetic fields. We will now deal with objects which are very commonly used in practical engineering fields.Although they are too much of idealization ,yet they are so important to know that the entire study of electrodynamics is incomplete without them.I expect Rohina and Rahul that you went through the reference for Gauss law I gave you.
I will like you to take a brief review of Gauss law and Ampere's Law before we proceed any further.To begin lets consider a simple case of a wire of infinite length . Yes.By the BiotSavart law we can get the field at each point , but by clever deductions from the elements of symmetry we can predict the magnetic lines of force at a glance.In this case the magnetic fields have to be tangential and the magnitude has to be constant for same r(the modulus of r as in cylindrical coordinate system) Now my question is how will one predict the direction of magnetic lines of force around the wire ?
(almost interrupting ) I know it ,Sir, its the right hand rule. That's good ! . Magnetic fields. Magnetic field. Magnetic field of an ideal cylindrical magnet with its axis of symmetry inside the image plane. The magnetic field is represented by magnetic field lines, which show the direction of the field at different points. In everyday life, magnetic fields are most often encountered as an invisible force created by permanent magnets which pull on ferromagnetic materials such as iron, cobalt or nickel and attract or repel other magnets.
Magnetic fields are very widely used throughout modern technology, particularly in electrical engineering and electromechanics. The Earth produces its own magnetic field, which is important in navigation. History[edit] One of the first drawings of a magnetic field, by René Descartes, 1644. Three discoveries challenged this foundation of magnetism, though. Extending these experiments, Ampère published his own successful model of magnetism in 1825. In 1850, Lord Kelvin, then known as William Thomson, distinguished between two magnetic fields now denoted H and B. Small Magnetic Receiving Loops. Revised Dec 22, 2005 corrected text errors and reworded some areas to make clearer Revised June 13 2006 to add link. Related pages coaxial cable and especially skin depth (Please read the Radiation and Fields page) Small Receiving Loops Small loops are often referred to as "magnetic radiators". Nothing is further from the truth! Field Impedance The ratio of electric to magnetic field sensitivity is sometimes called or can be described as the "field impedance".
Although fields have different ratios close to the antenna, at distances of about one wavelength the field impedances of small antennas are virtually indistinguishable from each other. Loop Antenna Fields It is the energy storage or reactive induction field response within λ/10 distance from the antenna that gives small "magnetic loop" and "electric dipole" antennas their names. Very close to a small loop antenna (but not necessarily near the open ends of the small loop where the tuning capacitor is) the magnetic field dominates. 'Magnetic emulsions' could clean up oil spills. 21 June 2012Last updated at 10:22 ET A standard magnet can be used to pull magnetic emulsions along a capillary Researchers have unveiled a molecule that can make "magnetic emulsions", which has the potential to revolutionise the chemical industry. Emulsions are blends which normally do not mix, like oil and water. The team's custom-made molecule, described in Soft Matter, acts as an "emulsifier", coating oily materials and acting to blend the liquids.
But because the molecule responds to magnetic fields, it could be put to use in cleaning up oil spills. The work is an extension of the "magnetic soap" the team reported in January and published in the journal Angewandte Chemie. The earlier work showed promise for industrial and cleanup applications, but study co-author Julian Eastoe of the University of Bristol said the new paper demonstrates "a practical application without a shadow of a doubt". It makes them part of an industry worth billions of pounds. Heads and tails.