03.01.2015 Views

handbook of modern sensors

handbook of modern sensors

handbook of modern sensors

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

52 3 Physical Principles <strong>of</strong> Sensing<br />

magnetic field<br />

in plane A<br />

Fig. 3.11. Electric current sets a circular magnetic field<br />

around a conductor.<br />

(A)<br />

(B)<br />

Fig. 3.12. Moving electron sets a magnetic field (A); superposition <strong>of</strong> field vectors results in a<br />

combined magnetic field <strong>of</strong> a magnet (B).<br />

atom. The electron movement constitutes a circular electric current around the atomic<br />

nucleus. That current is a cause for a small magnetic field. In other words, a spinning<br />

electron forms a permanent magnet <strong>of</strong> atomic dimensions. Now, let us imagine that<br />

many <strong>of</strong> such atomic magnets are aligned in an organized fashion (Fig. 3.12B), so<br />

that their magnetic fields add up. The process <strong>of</strong> magnetization then becomes quite<br />

obvious: Nothing is added or removed from the material—only the orientation <strong>of</strong><br />

atoms is made. The atomic magnets may be kept in the aligned position in some<br />

materials which have an appropriate chemical composition and a crystalline structure.<br />

Such materials are called ferromagnetics.<br />

3.3.1 Faraday’s Law<br />

Michael Faraday pondered the question, “If an electric current is capable <strong>of</strong> producing<br />

magnetism, is it possible that magnetism can be used to produce electricity” It took<br />

him 9 or 10 years to discover how. If an electric charge is moved across a magnetic<br />

field, a deflecting force is acting on that charge. It must be emphasized that it is<br />

not important what actually moves—either the charge or the source <strong>of</strong> the magnetic<br />

field. What matters is a relative displacement <strong>of</strong> those. A discovery that a moving

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!