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I'm reading Introduction to Electrodynamics by Griffiths and in chapter 4 when discussing induced dipoles and the effect of an electric field on an electrical insulator, it says the following:

These two regions of charge within the atom (positively charged nucleus and negatively charge electron cloud) are influenced by the field: the nucleus is pushed in the direction of the field, and the electrons the opposite way. In principle, if the field is large enough, it can pull the atom apart completely, "ionizing" it (the substance then becomes a conductor).

Emphasis mine and italicized comment added for clarity. I know it says in principle, indicating that this does not happen, but is it possible to ionize an insulator, say wood, with an extremely strong electric field? If it is theoretically possible, how strong would the electric field have to be in order for this to happen (orders of magnitude would be fine)? What would happen to a piece of wood in this kind of electric field? If it is not possible, is it due to limitations on the strength of electric field that we can actually create?

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  • $\begingroup$ The electric field that a dielectric can withstand before it gets ionized and breaks down in known as dielectric strength. $\endgroup$
    – Sam
    Jan 12 '20 at 4:56
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but is it possible to ionize an insulator, say wood, with an extremely strong electric field?

Yes it is possible. It's called dielectric breakdown.

If it is theoretically possible, how strong would the electric field have to be in order for this to happen (orders of magnitude would be fine)?

I don't know about wood, but most pure plastics (which are used as electrical insulation) have a dielectric strength in the range of 100 to 300 kV/cm. With additives it can be even higher (source: Polymer Properties Database). Actual values will vary depending on the test method used, especially the configuration of the test electrodes.

What would happen to a piece of wood in this kind of electric field?

I don't know. But you can probably Google up "Dielectric strength of wood" and find out. Be careful about wood as it is hygroscopic (absorbs water) with reduces the strength.

Hope this helps.

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