Struggling with tricky and important concepts in UPSC Prelims? The exam increasingly tests your conceptual clarity and ability to apply core ideas, especially in the most dynamic subjects: Science, Economy, and Environment (SEE).

UPSC Essentials’ new initiative, UPSC Prelims ‘SEE’ Snapshot, brings you, every Wednesday, a quick, exam-focused revision of key concepts. In each article, we pick three important current themes from Science, Economy, and Environment and decode them strictly through the Prelims lens—focusing on concepts and clarity.

If you missed the previous UPSC Prelims ‘SEE’ Snapshot: Talking cars, GDP rebasing and Nor’westers — quick look from the Indian Express, read it here.

The war in West Asia has resulted in a severe disruption to cooking gas supplies in India and driven up the price of LPG cylinders. This has led to a surge in the sale of induction cooktops in the country. How does it manage to cook food? The answer to that lies in the simple concept of electromagnetic induction. 

— Traditional gas stoves rely on combustion to create an open flame. But an induction cooktop bypasses this combustive chemical reaction. Its glass surface also remains relatively cool.

— Beneath the smooth ceramic or glass surface of an induction cooktop sits a tightly wound coil of copper wire. Switching the stove on completes the circuit and allows the flow of alternating current (AC) through the wire. The alternating current generates a rapidly fluctuating magnetic field directly above the cooktop.

— This changing magnetic field passes effortlessly through the glass surface and the surrounding air without heating either the surface or the air. This allows the cooktop surface to largely maintain its temperature. Any warmth it acquires is from contact with the hot pan.

— So how does the food get hot? Here’s where we get into some science, specifically Faraday’s Law of Induction. This law says that a changing magnetic field shall induce a voltage and, consequently, an electric current in any and all nearby electrical conductors — for example metal.

— So when the metal pan sits inside this intensely fluctuating magnetic field, it acts as a conductor. And localised, swirling electrical currents are generated inside the bottom of the pan itself. Known as eddy currents, these are pivotal to the heat-generation process.

— But metals such as iron are not perfect conductors. They have an inherent electrical resistance. So when the eddy currents swirl through the atomic structure of the pan’s base, they encounter this resistance. The ensuing electrical friction between the two converts the kinetic energy of the moving electrons directly into thermal energy (heat).

— When the pan itself becomes the primary heat source, the energy transfer also becomes efficient. Induction cooktops convert about 85% to 90% of their electrical energy directly into cooking heat. 

— Induction cooktops: works on electromagnetic induction, eddy currents, and resistance heating. Induction cooking is faster, safer and ultimately a highly resilient alternative to unpredictable fossil fuels. However, they are less durable than LPG stoves, harder to repair, dependent on electricity and not compatible with all cooking styles.

— LPG stoves: works on combustion and transfer heat mainly through radiation and convection. Traditional LPG stoves hover around 40% to 50% efficiency. However, a gas flame loses a massive amount of its thermal energy to the ambient air around the pot. 

Due to ongoing West Asian conflict India is facing pressure on the rupee and foreign exchange reserves. Last week, the Reserve Bank of India (RBI) said India’s foreign exchange reserves “remain adequate to provide cushion against external shocks”. Thus, it becomes important to know the forex reserves.

— Foreign exchange reserves are an important component of the Balance of Payment (BoP) and an essential element in the analysis of an economy’s external position. In times of crisis, adequate foreign exchange reserves give comfort, acting as a buffer and giving strength to a country’s macroeconomic fundamentals.

— The RBI has the primary responsibility of collection, compilation and dissemination of data relating to foreign exchange reserves.

— India’s foreign exchange reserves comprise foreign currency assets (FCA), gold, special drawing rights (SDRs) and reserve tranche position (RTP) in the International Monetary Fund (IMF). 

— Foreign exchange reserves are accumulated when there is absorption of the excess foreign exchange flows by the RBI through intervention in the foreign exchange market, aid receipts, interest receipts, and funding from the International Bank for Reconstruction and Development (IBRD), Asian Development Bank (ADB), International Development Association (IDA), etc. 

— Special Drawing Rights: SDRs are international foreign exchange reserve assets. Allocated to nations by the IMF, a SDR represents a claim to foreign currencies for which it may be exchanged in times of need. SDRs are the IMF’s unit of account. The value of SDRs is based on a basket of five currencies – the US dollar, the euro, the Chinese renminbi, the Japanese yen, and the pound sterling. As of March 13, India’s SDR holdings were worth $18.7 billion.

— Reserve Tranche Position: The primary means of financing the IMF is through members’ quotas. Each member of the IMF is assigned a quota, part of which is payable in SDRs or specified usable currencies (“reserve assets”), and part in the member’s own currency. The difference between a member’s quota and the IMF’s holdings of its currency is a country’s RTP. India’s reserve position is worth $4.8 billion.

The global climate is in a state of emergency as the earth is dealing with a record energy imbalance, the World Meteorological Organization (WMO) said in its recently released State of the Global Climate report 2025. The 2025 report for the first time included the earth’s energy imbalance as one of the key climate indicators. Earth’s energy imbalance is the highest in a sixty five-year record.

Core Concept

— According to WMO, earth’s energy balance measures the rate at which energy comes in and leaves the Earth system. 

— Under a stable climate, energy received by the earth from the sun is almost the same as the amount of outgoing energy. However, rising concentrations of atmospheric greenhouse gases — carbon dioxide, methane and nitrous oxide — to their maximum level in at least 800,000 years have upset this energy equilibrium on earth. 

— Albedo is the percentage of light that a surface reflects. It refers to how much energy a surface reflects. If everything is reflected, the albedo equals one. If 30% is reflected, the albedo is 0.3. The albedo of the Earth’s surface (atmosphere, ocean, and land) affects how much incoming solar energy, or light, is promptly reflected back into space. This could have an impact on the climate. 

— Dark colours have an albedo near 0, indicating that little or no energy is reflected. Pale colours have an albedo close to 100%, which means that almost all of the energy is reflected. 

— Notably, albedo affects incoming energy absorption, whereas energy imbalance measures net energy difference. So:

Let’s see how much can you recall

Consider the following statements:

1. In an induction cooktop, heat is generated directly in the cooking vessel due to eddy currents induced by a changing magnetic field.

2. India’s foreign exchange reserves are maintained and managed by the Reserve Bank of India.

3. Earth’s energy imbalance refers to the proportion of incoming solar radiation that is reflected back into space by the Earth’s surface and atmosphere.

How many of the statements given above are correct?

(a) Only one

(b) Only two

(c) All three

(d) None

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