What is the current in lightning: variable or constant?

Thunderstorms and dazzling flashes in the sky have always caused awe in mankind, forcing us to think about the power of nature. The question of what current flows in the lightning channel - variable or constant - is often the subject of heated debate among physics enthusiasts and laypeople. At first glance, it may seem that a discharge lasting a fraction of a second does not fall into any of the classical categories used in electrical engineering to describe the operation of household appliances.

However, atmospheric physics provides a clear answer, based on the direction of motion of charged particles. Unlike the current in the socket, which changes direction 50 or 60 times per second, the discharge in the atmosphere has a strictly defined direction of motion of electrons or ions. Understanding this difference is critical not only for academic knowledge, but also for the development of effective lightning protection systems for buildings and cars.

In this article, we will analyze in detail the mechanism of thunderstorm formation, consider its phase structure and find out why attempts to classify this phenomenon through the prism of household electrical engineering may be incorrect. You will learn about the colossal values of current and voltage, which are orders of magnitude higher than the capabilities of industrial generators.

The Physical Nature of Atmospheric Electricity

Before determining the type of current, it is necessary to understand how a giant spark discharge in the atmosphere arises in general. In the thunderstorm cloud there is a complex interaction of ice crystals and hailstones, which, when collided, exchange electric charges. Heavier hailstones, falling down, usually carry a negative charge, while lighter ice crystals are carried upwards, carrying a positive charge.

As a result of such sorting, a powerful center of negative electricity is formed at the bottom of the cloud, and a positive center at the top. Under the action of electrostatic induction on the surface of the earth under the cloud accumulates charge. When the electric field strength reaches a critical value, the air that is the dielectric is broken through and the discharge process begins.

⚠️ Attention: Air becomes a conductor only at a field strength of about 30,000 volts per centimeter. Until then, it reliably isolates the charged areas, allowing the accumulation of enormous energy.

The breakdown process begins with the so-called step leader - a faintly luminous channel that moves from cloud to earth in jerks. This leader is paving the way for the top rank. It is at this point that the main charge transfer occurs. It is important to note that the charge carriers move in one direction: from the region with an excess of electrons to the region with a deficiency of electrons.

Type of current: analysis of the direction of charge movement

Answering the main question of the article, it should be immediately indicated: the current in lightning is permanent (or, more precisely, pulsed direct current). This statement is based on a fundamental definition: direct current is the ordered motion of charged particles, the direction of which does not change over time. In the lightning channel, electrons move from the negatively charged base of the cloud to the positively charged earth (or vice versa, in the case of positive lightning), without making vibrational movements.

The alternating current that is used in our sockets is characterized by a sinusoidal change in the direction of the electron flow. In a standard network, the frequency is 50 Hz, which means 100 changes of direction per second. Nothing like that happens in lightning. Although the discharge itself can last a very short time (usually about 0.2–0.3 seconds for the entire series of pulses), during this time the direction of the current remains unchanged for each particular pulse.

Some researchers may object by pointing to a complex discharge oscillogram where peaks and slumps are observed. However, these changes are related to amplitude The power of the current, not its direction. The current can rise dramatically to hundreds of thousands of amperes and fall to almost zero, but the vector of charge movement does not invert, which is a key sign of direct current.

It is also worth mentioning the existence of different types of lightning. About 90-95% of all discharges are negative lightning bolts that carry a negative charge to the ground. However, there are also positive lightning that originate in the upper positive part of the cloud. In this case, the current flows from the ground to the cloud, but still remains. unidirectional during the pulse.

Discharge phase structure and temporal characteristics

Lightning is not a one-time event, but a complex physical process consisting of several stages. Understanding these phases helps us better understand why currents behave this way. A discharge usually consists of several repeated pulses following the same ionized channel.

The first phase is the formation of a leader. It is followed by the phase of the main discharge, when the main flow of charges rushes along the laid channel. It is at this moment that we see a bright flash and hear thunder. The channel may then go out, but if the cloud is still charged, the process can be repeated in the same way, a phenomenon called the "Cluster" phenomenon. flash-light.

• 🌩️ Preliminary break: Weak current, preparation of the conductive channel in the air.
• ⚡ Main rank: Maximum current, bright glow, a sharp increase in temperature to 30,000 ° C.
• 🔄 Repeated pulses: They follow in a few hundredths of a second, often merging in the eyes of the observer in one flash.

The duration of the lightning channel itself can be up to 1.5 seconds, if all repeated discharges are taken into account. However, each individual pulse of current lasts extremely short – on the order of several tens of microseconds for the growth phase and hundreds of microseconds for the recession phase. Such short-term and impulse nature do not allow the use of conventional transformers to "convert" lightning into a household network.

⚠️ Attention: Despite the short-term, the energy released during discharge is huge. The temperature in the lightning channel can be 5 times higher than the temperature of the surface of the Sun.

Why is the lightning writhing?

The trajectory of lightning depends on the heterogeneity of the air. The discharge follows the path of least resistance, flying around areas with denser or dryer air, which creates a characteristic broken line.

Parameters of thunderstorm discharge: force and tension

Characteristics of current in lightning are amazing and significantly exceed any artificially created man-made sources of energy in everyday conditions. Average values of parameters can vary widely depending on the power of the thunderstorm and the type of discharge.

The voltage at which the breakdown of the air gap occurs is calculated in millions of volts. The typical value is between 10 and 100 million volts (10–100 MV). This is the difference in potential required to overcome the electrical resistance of the air at an altitude of several kilometers.

The current strength in lightning also varies. For most categories, it is 20,000 – 30,000 amperes. However, there were cases when the current reached 200,000 amperes or more. For comparison: a conventional household outlet is designed for a current of 16 amperes, and the welding apparatus operates at a current of about 100-200 amperes.

Parameter	Average value	Maximum recorded	Unit of measurement
Current power	30 000	250 000	Ampere (A)
Tension.	50 000 000	1 000 000 000	Volt (V)
Pulse duration	0.0003	0.001	Seconds (c)
Channel temperature	30 000	50 000	Celsius degrees (°C)

Such extreme values lead to instantaneous evaporation of the conductor material if lightning strikes them without protection. Copper wires melt, concrete cracks due to instant evaporation of moisture inside, and the tree can catch fire. That is why the calculation of grounding systems is carried out taking into account these colossal values.

Hazard to technology and protection principles

Since the current in lightning is the most powerful pulse of direct current, it carries two main threats to technology: thermal and electromagnetic. Thermal impact is associated with the release of a huge amount of heat Q = I²Rt. Even the short-term passage of tens of thousands of amperes through a conductor with low resistance causes its instantaneous heating and destruction.

The second threat is electromagnetic pulse (EMP). A sharp change in current strength (pulse front) generates a powerful magnetic field that induces currents in all nearby conductive circuits. This can disable electronics even without lightning directly hitting a building. Sensitive chips burn from induced voltage.

For protection, lightning rods (lightning rods) are used, which take a blow on themselves and lead the current to the ground. The key element of protection is precisely grounding.The resistance of which must be minimal to ensure the current is spreading without dangerously increasing the potential. Usound (pulse overvoltage protection devices) are also used, which shunt excess voltage to the ground.

Myths and misconceptions about thunderstorms

There are many myths around lightning, some of which concern the nature of current. For example, there is an opinion that lightning can “charge” the car battery with direct current. That's completely wrong. Lightning energy is too large and chaotic, it will simply destroy the battery and the entire onboard network.

Another misconception is that rubber tires protect against lightning. In fact, the car protects people with a metal body that works like a Faraday cage. The current flows along the outer surface of the body and goes to the ground without affecting the cabin. Rubber at this voltage instantly breaks through or charred, without playing the role of an insulator.

• 🚫 Myth: A mobile phone attracts lightning. Reality: The radiation power of the phone is negligible and does not affect the electric field of the cloud.
• 🚫 Myth: Lightning never strikes twice in the same place. Reality: High objects (Ostankino Tower, skyscrapers) are struck dozens of times a year.
• 🚫 Myth: You can hide under a lonely tree. Reality: Wood is a great conductor (especially if it is wet) and often becomes a discharge target.

⚠️ Attention: When in a car during a thunderstorm, do not touch the metal parts of the body. Although the body protects against direct impact, currents can flow across the metal, creating a potential difference.

Frequently Asked Questions (FAQ)

Can lightning power be used to power homes?

Theoretically, the energy in lightning is great, but practically this is impossible. The problem is the short-term momentum (microseconds) and the enormous power that no battery can take without breaking. In addition, the unpredictability of lightning makes it impossible to create a stable power supply system.

Why is thunder heard after the flash?

Light travels at a speed of 300,000 km/s and reaches us almost instantly. The sound (thunder) moves much slower – about 340 meters per second. The time difference allows you to estimate the distance to the epicenter of the thunderstorm: every 3 seconds of sound delay is about 1 kilometer of distance.

Is lightning dangerous if it hits 100 meters from home?

Yes, dangerous. Even without a direct hit, a powerful electromagnetic pulse can bring currents to the wiring of the house and burn the equipment included in the socket. Stepping voltage is also dangerous if you are in an open space near the impact site.

Is there a ball lightning and what is the current?

Ball lightning is a rare and not fully studied natural phenomenon. It is assumed that this is a clot of plasma that exists for a long time. The nature of the current inside it may differ from linear lightning, perhaps there are vortex movements of charges, but exact scientific confirmation is not yet available.