0
$\begingroup$

Electromagnetic wave have magnetic and electric component but what is the proof for that? How "non electrostatic" electric field can be detected around coil?

$\endgroup$
3
  • 1
    $\begingroup$ We can make both electric and magnetic antennas. Ideally they will be responding only to one component of the field. A short dipole is an electric antenna, a small coil (relative to the wavelength) is a magnetic antenna. While these are not as efficient as well matched resonant antennas, they can still pick up these components independently and we can show the phase relationships that we expect from an electromagnetic wave. $\endgroup$
    – CuriousOne
    Commented Jul 27, 2016 at 8:47
  • 1
    $\begingroup$ For a radio wave the animated diagram in this Wikipedia article on Antennas shows how the electric field of the electromagnetic wave exerts a force on the electrons in the antenna and hence sents up currents and voltages in the antenna. en.wikipedia.org/wiki/Antenna_(radio) $\endgroup$
    – Farcher
    Commented Jul 27, 2016 at 9:18
  • $\begingroup$ In principle you could observe motion of a charged object due to the electric field of a radio wave. $\endgroup$ Commented Jul 27, 2016 at 22:18

1 Answer 1

3
$\begingroup$

Any electric charge would experience a force due to an electric field. Therefore, the electric field in electromagnetic waves produces currents in antennas. It happens all the time in wireless communication.

In the case of an electrostatically charged dielectric such as a plastic foil, the charges would tend to polarize the charges in any uncharged dielectric material that it comes in contact with. Any charge has a static electric field around it. This electric field produces an attractive or repulsive force depending on the sign of the charges involved. So, say the eletrostatically charged dielectric contains positive charges. Then it would attract negative charges and repulse positive charges in the uncharged dielectric. This causes polarization. The negative charges would now attract the positively charged dielectric. One observes this phenomenon as the tendency of electrostatically charged material to cling to things.

$\endgroup$
6
  • $\begingroup$ "electric charge would experience a force due to an electric field" what do you mean by that? when I place charged foil near coil with time varying current ,foil will experience force? repulsive ,attractive? $\endgroup$
    – szufla
    Commented Jul 27, 2016 at 9:06
  • 2
    $\begingroup$ The charges within the coil will experience a force and so the free electrons in the foil wil move and so a current is produced in the foil. That is how an induction furnace works. en.wikipedia.org/wiki/Induction_heating $\endgroup$
    – Farcher
    Commented Jul 27, 2016 at 9:21
  • $\begingroup$ no no,the foil is made of plastic and charged electrostaticly,so? $\endgroup$
    – szufla
    Commented Jul 27, 2016 at 12:47
  • $\begingroup$ @szufla, are you asking why an electric field would cause an electric charge to feel a force in general? Or as you in particular interested in the case when this electrostatically charged foil is placed in an electric field? $\endgroup$ Commented Jul 29, 2016 at 4:24
  • $\begingroup$ the second one,an charged plastic foil is placed near pulsating coil that emits EMF (induced electric field) or rotating magnet, like so: maxwellsociety.net/images/FaradayParadox/image565.gif $\endgroup$
    – szufla
    Commented Jul 31, 2016 at 2:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.