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Critical Topics and Their Significance for the UPSC CSE Examination on November 12, 2024

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How do lightning rods prevent lightning strikes from reaching people?

For Preliminary Examination:  Current events of antional and international importance

For Mains Examination: GS I - WOrld Geography

Context:

While a lightning strike occurs between a cloud and an object on or near the ground, it takes the path of least resistance, which means it moves towards the closest object with the highest electric potential

Read about:

What is Lightining?

Challenges with Lightining

Key takeaways:

The increasing frequency and severity of lightning strikes worldwide due to climate change pose significant risks, causing around 24,000 fatalities annually. In India alone, lightning killed 2,887 individuals in 2022. Many have petitioned for lightning strikes to be classified as a natural disaster in India, which would enable survivors to access formal support systems. In light of these dangers, lightning rods serve a crucial role in deflecting strikes away from people.

Understanding Lightning

Lightning is a result of electrical discharge occurring between charged particles in clouds and the earth. Objects behave as electrical conductors or insulators depending on the electrical energy they encounter. Normally, air is an insulator and does not allow electric charges to pass through. However, under a high voltage of about 3 million volts per meter, air's insulating properties break down, allowing it to carry an electrical current.

When the electrical charges within a cloud reach a threshold beyond the air’s insulating ability, a lightning strike can occur.

How Lightning Rods Work

When lightning seeks to discharge between a cloud and an object near the ground, it travels along the easiest route, typically aiming for the closest object with the highest electric potential.

According to Adhip Agarwala, an assistant professor of physics at IIT Kanpur, lightning rods are designed with pointed tips to strengthen the electric field around them. This field ionizes the surrounding air, creating a pathway for the current to flow through the rod. Visualize the lightning strike as a hand reaching out for help—the rod acts as the strongest “hand” for the lightning to connect with, drawing it away from other structures and directing it safely to the ground. Standing under trees in an open field, like farmland, is dangerous for this reason.

Where the Lightning Rod’s Current Goes

Electric currents flow from areas of high electric potential to those of lower potential, similar to heat moving from hot to cold. The earth itself has low electric potential, so the rod is grounded with a wire running from the building’s top to the ground, allowing charges to disperse safely. Earth acts like a reservoir, absorbing the electric charge without “filling up.” However, some regions of the ground may be better at dissipating the charge than others.

To protect electrical systems from surges caused by lightning strikes, engineers connect the grounding wire to a line that redirects high currents, preventing damage to devices with lower current tolerance. This configuration is known as a lightning arrester.

Can Lightning Miss a Lightning Rod?

Lightning rods may be ineffective if improperly positioned, poorly grounded, or if there are competing structures nearby. Issues with the design, installation angle, or corrosion due to lack of maintenance may also cause failure. Additionally, a ground-to-cloud discharge can sometimes bypass the rod. To ensure reliability, engineers design rods to be within the minimum distance lightning travels in each “step” toward the ground.

Risks of Lightning Rods

Lightning rods and their connected components are designed to safely transport charges into the ground. If the grounding wire bends into a U shape, the arms of the U must be far enough apart to avoid an arc that could short-circuit the conductor. The grounding area is also chosen for its high conductivity to help the wire disperse charges efficiently. In the 1960s, Herbert Ufer, a U.S. engineer, introduced a concrete-encased electrode, a grounding system with better conductivity than typical soil.

International standards set by the International Electrotechnical Commission outline safety parameters, potential failure points, and risk assessment priorities to guide engineers and policymakers in the design and installation of lightning rods

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