I want to do electrostatic shielding but I am not sure if blocking only the line of sight is enough.

Imagine that there is an electrically charged sphere, $1 cm$ in diameter, just sitting stationary in free space. Some distance away, for example, $3cm$ is another sphere with neutral charge that I want to shield from the electric field of the charged sphere.

Is it enough if I put electrostatic shielding: a circular copper plate with $1cm$ diameter between them? Or will the electric field go around the copper that's only blocking the direct line of sight and affect the neutral sphere I want to protect from electric field?


To the question in the title: No, electric field does not go around obstacles.

What really happens is that the matter (inside the obstacles) is influenced by the field going through it displacing the charges in the matter.

So, that for example, charges in a conductor displace to such an extent (they can because the electrons are free) that the net electric field is zero inside the conductor. Note that the original electric field does go through the conducting obstacle; it is just that the new electric field (of the conductor) exactly cancels it.

If the obstacle was a dielectric, the charges cannot displace so much that the electric field is exactly canceled. But they do reduce it by a ratio (the dielectric ratio).

To the next part: A plate alone will not do. The electric field still passes through (as explained above) - it is just neutralized inside the plate affecting the surroundings very insignificantly.

What you can do is cover the complete neutral sphere with a conductor.

  • $\begingroup$ Can you please tell me more about how dielectric barrier can reduce it? I was thinking that any dielectric will only strenghten the field becose to my current understanding a dielectric constant is like force multiplier and since all dielectrics have higher dielectric constant than air then they all must strenghted the field,not decrease it like you say.I was thinking that If I fill the free space from thr charged object up to the distance of the object I want to shield with silicon dioxide with 3.9 costant,then the field will be 390% stronger,not reduced... please explain the blocking effect $\endgroup$ – wav scientist Sep 8 '17 at 21:34
  • $\begingroup$ The dielectric constant appears in the denominator of the term for the Electric field. Remember $\frac{1}{4\pi\epsilon}$? Take a look: en.wikipedia.org/wiki/Dielectric $\endgroup$ – Abhijeet Melkani Sep 8 '17 at 21:56
  • $\begingroup$ Where $\epsilon = K.\epsilon_o$ where K is the dielectric constant. $\endgroup$ – Abhijeet Melkani Sep 8 '17 at 21:57
  • $\begingroup$ I dont understand mathematical equations,can you explain it to me in simplified way? They put dielectrics between capacitor electrodes to increase the field strenght,with my sitation charged object + dielectric in between + neutral object I want to shield,it all looks like capacitor to me,I cant imagine how dielectric can be used to reduce the field behind it when used as barrier/shield. $\endgroup$ – wav scientist Sep 8 '17 at 22:21
  • $\begingroup$ A capacitor is a device used to store charge - and the major problem with any capacitor is the field generated by the charges because that tries to neutralize the charges. Therefore, one wishes to maximize the charge stored while keeping the field minimum. In fact, the capacity (capacitance) is measured as charge stored per unit field strength (loosely). Thus, even in capacitors dielectrics are used to reduce field strength. $\endgroup$ – Abhijeet Melkani Sep 9 '17 at 5:50

No (but yes).
Your copper shield will have opposite charges on opposite sides as shown here. enter image description here
The field does not go around the conductor, nor does it go through it.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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