Under what conditions can wood, considered an electrical insulator, conduct current

Wood is said to be a good electrical insulator. That is why, in the past, TV and radio housings were made of wood. In addition to being insulating, they were also non-magnetizable, which ensured that the appliances worked properly and safely. You have probably also heard that if you sit on a wooden chair to change a light bulb, nothing can happen because wood does not conduct electricity. However, if it is raining lightning, the most dangerous place is under a tree. There are countless spectacular images of electricity discharging through the only tree in the landscape. This begs the question: does wood conduct electricity or not? When and why wood turns from an insulator into a conductor of electricity, find out below.

Is wood an electrical insulator or not?

It depends on the moisture content. The lower the moisture content, the better the wood is as an electrical insulator. Anhydrous wood does not conduct current at all. At a water content of 8-12%, its electrical conductive capacity is very low, and wood is still considered an insulator. As the water content increases, so does the ability of the wood to conduct current. This capacity also depends on other factors which we will discuss in a moment.

The difference between the above examples is not only the difference in humidity but also the strength of the flow of electricity. When we talk about the normal electric current needed to make a light bulb light or an appliance work, we are talking about the ability of the wood to let the current pass through or not. But if it is a very strong electrical current, such as lightning or power lines, then the wood is simply passed through, and its ability to resist the current is useless. A wooden pole will be struck in the same way as a tree, regardless of moisture content. It is therefore recommended to avoid using wood near power lines, e.g. climbing a wooden ladder for a work at height.

What determines the electrical insulating properties of wood

Electric current is the movement of a flow of electric charges represented by electrons or ions. Some materials have the ability to let this flow, others do not. This ability depends on the nature of the materials and their chemical composition. The presence of free electrons or ions in the composition makes the material a good conductor of electricity, whereas their absence means that it is capable of insulating. Metals have their electrons loosely bound to the nucleus and so electric current is easily conducted. In the basic building blocks of wood - lignin, cellulose and hemicellulose - there are no free ions and the electrons are strongly attracted to the nucleus. The electric current does not find particles to carry it away and so the flow of charges is stopped.

Another barrier to electricity is the porosity of wood. As the water leaves the wood, voids are left inside the wood where air can penetrate, which is unable to carry electricity. This is why wood becomes increasingly insulating as air replaces water.

Electrical resistance of wood

The ability of wood to resist the passage of electric current is called relectrical resistance. It is the most important electrical property of wood and depends on moisture, temperature, species, fiber direction, part size, applied voltage.

Humidity is the most important. The lower it is, the better the wood insulates. Increasing the moisture level in the water-bound range, i.e. up to 30% moisture, greatly changes the behavior of wood. It is on this property that the measurement of wood moisture with the electric moisture meter is based.

Temperature is inversely proportional to the electrical resistance. The higher the temperature, the lower the electrical resistance. This is because the higher temperature makes the free ions in the water more active.

Species. Wood is not a homogeneous material and the species are very different. Understandably, the behavior is also different. How the pores are arranged, the content of salts and other similar substances, the air inside are all factors that influence the electrical conductivity.

Fiber direction. At the same humidity the conductivity can be different. This is also due to the percentage of longitudinal fibers. The higher this percentage, the higher the conductivity of the species. Such species are suitable for pyrography (willow, poplar, frasin, molid).

Dimensions of the piece. The longer and thinner the wood, the easier the current is transmitted. Shorter and thicker pieces have greater electrical insulating capacity.

What turns wood from an insulator into an electrical conductor

It is the water content that makes the difference. But it is not the water itself that conducts the current and the salts dissolved in it. Pure 100% 100% water is a perfect electrical insulator. When salts are dissolved in water, they give rise to ions and the water becomes an electrolyte that conducts current.

Nature's water, the water that drives the food into the standing tree and that must be removed from the felled tree to turn it into good wood for buildingi or furniture, it is not pure. It contains many dissolved salts that become the carrier of electric current. Once the wood is dry, some of the salts come out, others remain inside in solid form, unable to conduct current. When the water returns, the salts dissolve and the electrolyte solution reappears.

The salts most commonly used to increase the conductivity of wood are sodium chloride (table salt) and sodium bicarbonate (baking soda).

Finished wood can become a better conductor of electricity if it is finished with high-gloss varnish or metal-containing paints or patinas. Antique pieces with gilded or silvered edges or profiles conduct current better than plain pieces.

Drawing in wood with electricity

The ability of wet wood to conduct current is used to obtain so-called Lichtenberg figures. These are specific drawings obtained by burning wood with an electric current and resemble electrical discharges in air. It is a very dangerous method because it takes at least 2000 volts to produce a small drawing. Information about the method herebut the recommendation is not to apply it because it is far too dangerous.

Water with baking soda is used to make wood into a material that conducts electricity. Table salt is not recommended because of the toxic chlorine compounds that are formed at the high temperature developed by the discharge of thousands of volts.

I hope you find the above information useful. As always, additions are welcome. And if you have any questions or queries, please leave them below in the space provided. I will be sure to reply.