# Pollen Particle Attracted to TV due to Which Force?

A pollen particle has no charge so I cannot understand how the Lorentz force $\bar{F} = q \bar{E} + q(\bar{v} \times \bar{B} )$ could explain the event. I speculated that it is because of the electric field that is generated to the dipole with a charge in the TV and the distance, more here. I have not yet confirmed that it would attract the pollen particle. Any better ideas?

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What makes you so sure that the pollen has no charge? In Millikan's famous oil drop experiment, he relied on the charging of the drops caused by friction with the nozzle. It doesn't take much to charge an object and the electric field generated by a tube type television can be substantial so it wouldn't have to be charged much. – AdamRedwine Aug 29 '11 at 20:40
I don't see what's wrong with your dipole hypothesis. A neutral pollen particle near the strong fields around a CRT would become polarised and attracted to the TV. – Dan Piponi Aug 29 '11 at 21:03
Thanks, that helps. At that rate I think you and user207442 are on the right track. – AdamRedwine Aug 29 '11 at 21:29
@user207442: that's the kind of thing you'd want to post as an answer (in expanded form). – David Z Aug 30 '11 at 3:36
@AdamRedwine: wait -- I think user207442 is hitting the nail. The particle needs no charge because of the polarization itself! If you define the statement "charge is zero" as $\sum_{i} q_{i} =0$, you can still have partial charges due to the electric field with the dipole (momentary charges on the particle). So $\bar{E}$ covered here formatted so $\bar{F} = q\bar{E}$ attracts the pollen to the TV, at least. What about the magnetic field? – hhh Aug 30 '11 at 15:23

CRT displays have a fairly strong electric charge and this induces a dipole moment in the pollen particle itself causing it to be attracted to the screen.

Somewhat related, the hairs on the bodies of some bees become electrically charged and this attracts pollen particles. Exercise 51 on page 602 of this document http://cyber.gwc.cccd.edu/faculty/kstein/H_R_Ch_22.pdf will give you a ball park figure for the possible strength of this attraction. It assumes a neutral pollen particle.

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I do not know to what special pollen your professor refers to, but pollen is often charged at least as this measurement described in the publication abstract found:

Under fair weather conditions, a weak electric field exists between negative charge induced on the surface of plants and positive charge in the air. This field is magnified around points (e.g. stigmas) and can reach values up to 3×106 V m−1. If wind-dispersed pollen grains are electrically charged, the electrostatic force (which is the product of the pollen's charge and the electric field at the pollen's location) could influence pollen capture. In this article, we report measurements of the electrostatic charge carried by wind-dispersed pollen grains. Pollen charge was measured using an adaptation of the Millikan oil-drop experiment for seven anemophilous plants. Acer rubrum, Cedrus atlantica, Cedrus deodara, Juniperus virginiana, Pinus taeda, Plantago lanceolata and Ulmus alata. All species had charged pollen, some were positive others negative. The distributions (number of pollen grains as a function of charge) were bipolar and roughly centered about zero although some distributions were skewed towards positive charges. Most pollen carried small amounts of charge, 0.8 fC in magnitude, on average. A few carried charges up to 40 fC. For Juniperus, pollen charges were also measured in nature and these results concurred with those found in the laboratory. For nearly all charged pollen grains, the likelihood that electrostatics influence pollen capture is evident.

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no you are walking the wrong path, my lecturer would reward you with negative points if this was an exam. Please, read the comments. I think the point what he was trying to say is "polarization", no quantum-physics research topic or anything like that. Even though you have particles having no charge, they can be attracted to the TV due to momentary charges. So you will get a Lorentz force due to $\bar{E}$ but what about magnetic field? – hhh Aug 30 '11 at 15:30
The link says nothing about quantum physics, it is all classical. I am just pointing out that in real life pollen carries some charge that has been measured, so cannot be used as an example of a small particle with no charge. – anna v Aug 30 '11 at 19:15
The CRT has one or more electron gun that hits the back of the front of the TV, building up electrostatic forces . Magnetic coils are far in the neck of the vacuum tube and will not be affecting any dust. You can feel the electrostatic field being built up by the electron gun if you touch a lit TV. – anna v Aug 30 '11 at 19:32