• The 1982 Asian Games served as a turning point for Indian sports policy. In its aftermath, the government established a separate Department of Sports under the Ministry of Human Resource Development.
• Capitalizing on the momentum, India introduced its first National Sports Policy (NSP) in 1984, which aimed to enhance sports infrastructure, encourage mass participation, and elevate performance at the elite level.
• The policy also emphasized the integration of sports into the educational system, a concept that was formally included in the 1986 National Education Policy. That year also saw the creation of the Sports Authority of India (SAI), tasked with executing sports policies and managing athlete development programs.
• However, between 1986 and 2000, while the global sports landscape saw significant growth, India’s progress remained limited. With sports falling under the jurisdiction of state governments as per the Constitution, and with only a modest allocation from the central government, broader societal and private sector engagement was largely absent.
• The policies during this time were underdeveloped, and their execution lacked consistency. Moreover, India’s sluggish economy during the 1980s further hindered sports development.
• The economic liberalisation of 1991 marked a pivotal shift, bringing with it cultural transformation. The advent of cable television, increased international exposure, and a growing middle class sparked greater interest and ambition in sports.
• A Draft National Sports Policy was introduced in 1997, proposing that state governments focus on grassroots development while the central government prioritized elite sports. However, the draft was never formally adopted

EPABX stands for Electronic Private Automatic Branch Exchange.

It is an automated telephone exchange system that is privately owned and used by an organization. The main purpose of EPABX is to manage multiple telephone lines without the need for a human operator. It handles both internal calls (within the organization) and external calls (to and from the outside world)

2.1.How does it work?

Imagine an office with 30 employees, each having a telephone. Instead of giving each person a direct line to the public telephone network (which would be expensive), the organization installs one EPABX system connected to a few external lines from the telephone company (say, 5 lines).

• Internally, employees can call each other using extension numbers (e.g., 101, 102).

• For outside calls, the EPABX routes the call through one of the external lines.

• If someone calls the office from outside, the EPABX directs the call to the correct extension or department.

The handling of incoming calls varies depending on how the EPABX system is set up. Calls from the Public Switched Telephone Network (PSTN) are directed to one of the available trunk lines connected to the EPABX. In older configurations, a receptionist was required to manually transfer the calls. However, in modern systems, automatic EPABX allows callers to reach specific extensions directly by dialing them.

More sophisticated digital EPABX systems can be configured with interactive voice response (IVR) menus. These menus prompt callers to input the desired extension number or automatically forward the call to preset destinations, such as the front desk. The internal switching mechanism then connects the call to the selected extension without needing human assistance

4. How does the switching mechanism work?

• The switching mechanism serves as the core function of any EPABX system, responsible for directing calls to their intended extensions.
• In the earlier models from the 1970s and 1980s, electromechanical switching devices like crossbar relays were commonly used. These systems operated in a way similar to turning a ceiling fan's speed regulator—where adjusting a dial shifted internal components to complete a circuit.
• When a user made a call, an electromagnet would trigger a copper strip to move, creating a physical bridge between two lines, thus allowing voice transmission between phones.
• A basic electrical switch works like a faucet—flip it on and electricity flows, flip it off and it stops. However, the switches in EPABX systems are much more sophisticated.
• One of the simplest types is the "single pole, single throw" switch—comparable to a regular light switch. A step up in complexity is the "single pole, double throw" switch, which has one input but two possible output paths—similar to a fan regulator with multiple speed settings. The "double pole, double throw" switch is even more advanced, with two input sources and four output options.
• Think of EPABX call routing like managing a railway yard. An incoming call acts like a train arriving at a major station with several platforms. The EPABX functions like the railway signal system, ensuring the call reaches the right extension, much like a train being guided to the correct platform.
• When someone dials an internal number, the EPABX system activates a series of relay switches, connecting the caller to the appropriate recipient. This process resembles aligning railway tracks to ensure a train travels smoothly to its destination. Once the call ends, the relays reset, ready for the next communication.
• You can also imagine the switching structure as a layered network. The main line splits into several branch lines—like platforms—and each branch leads to a set of sub-extensions.
• For instance, branch 1 might contain extensions 11 to 14; branch 2, extensions 21 to 24; and so on. So, if someone calls extension 104, the switch activates a specific relay path that directs the call through the right combination of connections to reach its endpoint

 5. Way Forward

The expansion of electronic technology during the 1980s led to the replacement of electromechanical switches with fully electronic systems. More sophisticated digital setups began converting voice signals into digital form using Pulse Code Modulation (PCM). These systems also implemented Time Division Multiplexing (TDM), a method that allocates specific time slots to each voice channel, allowing several users to communicate through the intercom system at the same time without interference.

As internet technologies advanced, Voice over Internet Protocol (VoIP) became a key component in modern PBX systems. Similar to how an IP address ensures emails reach the correct recipient, voice and multimedia data are now routed through the internet to the intended phone device.

The transition from mechanical relays to digital switching has greatly improved the performance and flexibility of EPABX systems. Today’s versions are integrated with advanced communication tools and support features such as voicemail, call recording, automated call handling, and interactive voice menus, making them highly efficient for both internal and external communication needs

SOLAR ENERGY SYSTEMS

• Electricity can primarily be generated through two key methods. The first is electromagnetic induction, a principle discovered by Michael Faraday in 1821, which became commercially applicable around 1890. Even today, this method remains central to most of the world's electricity generation.
• The second approach involves photovoltaic (PV) technology, which relies on semiconductor materials like elemental silicon to convert sunlight directly into electricity. The photovoltaic effect was first observed by Alexander Becquerel in 1839.
• However, it wasn't until 1954 that a functional and efficient solar cell was developed at Bell Laboratories by Chapin, Fuller, and Pearson using doped silicon.
• This achievement was made possible thanks to two pivotal scientific contributions: Albert Einstein’s Nobel Prize-winning explanation of the photoelectric effect, and Jan Czochralski’s method for producing single-crystal silicon, which remains the foundation for most PV cells today.
• Unlike PV systems that feed regulated, taxable electricity into national power grids, technologies such as solar water heaters, solar air heaters, and solar-based cooling systems usually operate independently.
• For example, solar cooling uses an absorption refrigeration process that can cool interiors to as low as 19°C even when the ambient temperature hits 40°C. These standalone technologies are similar to PV panels used in off-grid regions, typically for purposes like charging batteries and powering basic lighting systems.
• Globally, solar insolation—the measure of solar energy received—varies significantly by region. Though solar energy is plentiful, it is scattered over wide areas, making it less concentrated.
• To harness it effectively, various focusing technologies such as parabolic troughs, Fresnel lenses, and other solar concentrators are employed for tasks ranging from cooking and water desalination to thermal heating and electricity production

 

3. How does sunlight generate power?

 

• Photovoltaic (PV) cells are typically composed of semiconducting materials like elemental silicon. Unlike metals such as copper, which are Ohmic conductors (their electrical resistance increases with temperature), silicon behaves as a non-Ohmic material. At room temperature, silicon is a poor conductor, but its conductivity improves as it gets warmer.
• From a quantum mechanical perspective, electrical conduction occurs when electrons occupy a higher energy level known as the conduction band, where they can move freely, similar to how water flows in the ocean. Electrons that remain in the valence band, a lower-energy state, are immobile and do not contribute to electrical current.
• To move an electron from the valence band to the conduction band, energy must be supplied. This energy can come from thermal excitation (increased atomic motion at higher temperatures) or from other energy sources such as light.
• Light, depending on the experiment, behaves either as a wave or as individual energy packets called photons. When photons strike electrons in the valence band, they can transfer energy to the electrons, allowing them to rise to the conduction band—if the photon’s energy matches or exceeds the required energy gap.
• This energy gap, known as the band gap and measured in electron volts (eV), must be matched precisely by the photon’s energy for the transition to occur. If a photon has more energy than necessary, the excess is converted to heat, which not only leads to energy loss but can also cause electrons to escape.
• Besides the energy requirement, there's also a symmetry condition for these transitions, though it plays a lesser role in this context. Due to these constraints, silicon-based PV cells cannot utilize the entire solar spectrum efficiently—around 50.4% of the sunlight is unusable. About 20.2% of photons lack sufficient energy to initiate the transition, while 30.2% carry excess energy that’s lost as heat.
• Other semiconducting materials like gallium arsenide, cadmium telluride, and copper indium selenide can absorb different parts of the solar spectrum more effectively. However, their widespread use is restricted by challenges such as limited availability, environmental hazards, and handling complexities

 

4. Silicon Solar Cells

 

 

• In silicon-based photovoltaic (PV) cells, trace amounts of phosphorus and boron are intentionally introduced to create regions that either have an excess of electrons or a shortage of them (known as "holes").
• This results in the formation of a p-n junction, where the difference in electrical charge establishes an electric field. When sunlight hits the surface, this setup acts like a battery, generating an electric potential that drives current.
• When an external circuit is connected, electrons travel from the negatively charged side through the load toward the positively charged side, completing the circuit. This process can continue as long as the cell is exposed to light.
• However, even within the 49.6% of the solar spectrum that is usable, several energy losses still occur. For example, PV cells often heat up to 30–40°C above the surrounding temperature, and this radiative heat loss accounts for around 7% of energy loss.
• An additional 10% loss is caused by differences in the mobility of positive and negative charges, a phenomenon known as the saturation effect, which reduces the generated voltage over time.
• These factors contribute to a theoretical efficiency ceiling of 33.7% for single-junction silicon PV cells, a value known as the Shockley-Queisser limit. Moreover, practical inefficiencies such as non-uniform sunlight exposure and manufacturing inconsistencies between cells (which cause differences in open-circuit voltage) also reduce performance.
• When real-world losses like converting DC to AC and managing peak power output are considered, the actual efficiency of silicon-based crystalline PV cells averages about 25% in laboratory settings, while the best commercial models achieve roughly 20% efficiency. By comparison, natural photosynthesis captures only 3–6% of the sunlight it receives

 

5. What can solar energy and cannot do?

 

• Because natural silicon reflects a significant amount of light, photovoltaic (PV) cells are coated with a transparent anti-reflective layer, typically made from tin oxide or silicon nitride, which also gives them their distinctive blue hue.
• Unlike biological photosystems, which assemble proteins using minimal energy at ambient temperatures, PV technology demands high energy inputs during manufacturing.
• The production of PV cells starts with the Czochralski process, which purifies elemental silicon to about 99% purity by melting and slowly forming it into single-crystal ingots. When these ingots are sliced into thin wafers, roughly 20% of the material is lost as silicon dust.
• Due to the high costs associated with single-crystal silicon, alternative techniques have been developed — for instance, ribbon technology avoids sawing losses, while amorphous silicon cells are more economical. Their natural structural imperfections can be corrected by adding hydrogen, improving performance.
• To capture a wider range of the solar spectrum, multijunction amorphous silicon cells have been engineered. These can theoretically reach efficiencies as high as 42%, though real-world performance typically peaks around 24%. PV technologies are broadly grouped into three generations:

1. First-generation uses thick crystalline wafers (~200 µm),

2. Second-generation relies on thin-film wafers (1–10 µm), and

3. Third-generation includes advanced designs like multijunction tandem cells and quantum dots, which can generate more charge carriers per photon, potentially surpassing the Shockley–Queisser efficiency limit.

 

• The cost of PV-generated electricity has declined sharply—from $4–5 per watt in 2010 to about $2.8 per watt in 2023 (and as low as $1.27 per watt for utility-scale systems), nearly achieving the U.S. SunShot Initiative’s goal of $1 per watt. Breaking down system costs:

• Modules account for 38%,

• Inverters and other electronics for 8%,

• Wiring and mounting contribute 22%, and

• The remaining 33% is spent on balance-of-system (BoS) costs, including labour, permits, administrative expenses, and profit margins.

• Since single-crystal silicon cells are close to their theoretical peak, future cost reductions are most likely in the BoS components. In terms of durability, PV systems lose efficiency at a rate of about 0.5% per year, with most modules lasting 20 to 25 years.
• Interestingly, although tropical and desert climates receive higher solar irradiance, PV modules perform more efficiently in cool, clear conditions due to reduced thermal losses. This makes it challenging for low- and middle-income countries — many of which lie in tropical zones — to fully leverage PV systems, especially given infrastructural limitations and climatic constraints.
• Additionally, air pollution can block 2–11% of solar radiation, and dust accumulation (soiling) can cause an extra 3–4% loss annually.
• Cleaning solar panels is both risky and water-intensive, since the panels become electrically active under sunlight. In densely populated urban areas, PV systems may also intensify the urban heat island effect by trapping heat.
• While other solar technologies can offer some complementary benefits, the extent to which PV systems alone can support a fully carbon-neutral energy future remains a topic of active scientific debate

 

6. Government supported schemes

 

Jawaharlal Nehru National Solar Mission (JNNSM) – 2010

• Launched under the National Action Plan on Climate Change (NAPCC).

• Aimed to establish India as a global leader in solar energy.

• Target revised to 100 GW of solar capacity by 2022 (out of 175 GW total renewable energy target).

• Focus on both grid-connected and off-grid solar power systems.

PM-KUSUM (Pradhan Mantri Kisan Urja Suraksha evam Utthaan Mahabhiyan) – 2019

• Promotes the use of solar energy in the agriculture sector.

• Three components:

  • Component A: Solar power plants (up to 2 MW) on barren land.

  • Component B: Standalone solar-powered agricultural pumps.

  • Component C: Solarisation of existing grid-connected pumps

 

 

 

For Prelims: General issues on Environmental ecology, Bio-diversity & climate change For Mains: GS-III: Conservation, environmental pollution and degradation, environmental impact assessment.

 

Previous Year Questions   1.Consider the following statements: (2016) The International Solar Alliance was launched at the United Nations Climate Change Conference in 2015. The Alliance includes all the member countries of the United Nations. Which of the statements given above is/are correct? (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2 Answer (a)   Statement 1 is correct. The International Solar Alliance (ISA) was launched at the United Nations Climate Change Conference (COP21) in 2015 in Paris. Statement 2 is incorrect. Initially, the ISA was intended for solar-rich countries lying fully or partially between the Tropics of Cancer and Capricorn. However, in subsequent years, the membership was expanded to include all UN member countries

 

Source: Indianexpress

 

 

SANTHAL REBELLION

 

 

 

1. Context

 

The landmark event in tribal history, referred to as Santhal Hul, completes 170 years today. Every year, the state of Jharkhand also celebrates June 30 as ‘Hul Diwas’, marking the beginning of the rebellion. On this occasion, let’s revisit this landmark event in Indian history and understand it from a broader perspective.

 

2. Santhal rebellion

 

• The Santhal uprising, known as ‘Hul’ (meaning revolution), began in 1855—two years prior to the 1857 revolt, which is often described as India’s first major struggle for independence.

• It represented a coordinated resistance against British colonial rule, where the Santhal community rose in defiance of widespread exploitation—both economic and social—inflicted by British authorities, allied landlords (zamindars), and corrupt moneylenders.

• This resistance movement, spearheaded by brothers Sidhu and Kanhu, gained support from as many as 32 different castes and communities.

• The roots of this revolt trace back to 1832, when the British East India Company established the Damin-i-Koh area within the Rajmahal Hills’ forested terrain. The region was designated for Santhals who had been relocated from parts of the Bengal Presidency, including Birbhum, Murshidabad, Bhagalpur, Barabhum, Manbhum, Palamau, and Chhotanagpur.

• Although the Santhals were promised land and farming opportunities in Damin-i-Koh, they were soon subjected to exploitative practices, including land dispossession and forced labour systems such as kamioti and harwahi. Over time, these abuses intensified under colonial supervision.

• The rebellion, which erupted in 1855, persisted with violent confrontations until 1856, when the British eventually suppressed it. Using advanced weaponry and war elephants, they crushed the uprising, during which both Sidhu and Kanhu lost their lives

 

 

3. About Santhals

 

• The Santhals were not indigenous to what is now known as the Santhal Pargana region, which comprises six districts—Dumka, Pakur, Godda, Sahibganj, Deoghar, and parts of Jamtara. Their migration began in the late 1700s from the Birbhum and Manbhum areas, located in present-day West Bengal.

• The devastating Bengal famine of 1770 prompted the Santhals to relocate. Around this time, the British sought their assistance. Following the introduction of the Permanent Settlement Act in 1790, the East India Company aimed to extend its agricultural control and revenue base.

• The Damin-i-Koh region, then densely forested, was designated for Santhal settlement to ensure a consistent tax income. However, after resettlement, the Santhals found themselves subjected to severe colonial exploitation.

• In present times, the Santhals constitute the third-largest tribal group in India, primarily residing in the states of Jharkhand, Bihar, Odisha, and West Bengal.

 

4. Other Tribal rebellions

 

Munda Rebellion:

• In 1899, Birsa Munda initiated the Ulgulan or Munda rebellion, employing guerrilla tactics and traditional weapons to resist British rule. He urged tribal communities to embrace the concept of Birsa Raj, advocating for the rejection of colonial laws and the refusal to pay rents.
• This uprising was one of the most strategically coordinated tribal movements, aiming to dismantle British governance, eliminate external influences, and establish a self-governed Munda territory. However, the British, with superior military power, quickly suppressed the revolt. Birsa Munda was captured on March 3, 1900, while resting with his followers in the Jamkopai forest near Chakradharpur.
• The rebellion had a lasting impact, contributing to the abolition of the begar (forced labour) system and influencing the creation of the Tenancy Act in 1903, which acknowledged the khuntkatti landholding rights. Later, the Chotanagpur Tenancy Act of 1908 restricted the transfer of tribal land to outsiders.

Paika Rebellion:

• 
  The Paika Rebellion of 1817, centered in Khurda (Odisha), is often regarded as a significant early resistance against British rule—sometimes even called the "first war of Indian independence."
• The Paikas, traditional soldiers under Odisha's kings, revolted after being stripped of their rent-free land grants. The deposition and exile of the Khurda king in 1803 and the imposition of new revenue policies deeply affected the Paikas, who lost both property and societal privileges.
• The rebellion escalated when around 400 Kondhs from Ghumusar rose against the British, prompting Bakshi Jagabandhu, the highest-ranking general of the exiled Khurda ruler, to lead the Paikas into battle. Although they engaged in intense combat across various locations, British forces gradually quelled the rebellion

Kol Revolt:

• In 1831, the Kols of Chhota Nagpur rebelled due to increasing encroachment on their lands by non-tribal settlers, a process enabled by new colonial land policies. Economic exploitation and dispossession led to widespread anger among the indigenous people.
• Leaders like Buddhu Bhagat, Joa Bhagat, and Madara Mahato spearheaded the revolt, which saw the participation of other tribes such as the Hos, Mundas, and Oraons.
• Armed mainly with traditional weapons, tribal fighters launched fierce attacks against British forces and local moneylenders. The uprising spanned regions like Ranchi, Hazaribagh, Palamau, and Manbhum, and lasted nearly two years before being crushed by the colonial administration

Bhil Uprising:

• The Bhils of the Khandesh region in Maharashtra rose against British intrusion in 1818, fearing exploitation under foreign rule. Sewaram led this resistance, but the movement was violently suppressed. A renewed revolt occurred in 1825, as the Bhils sought to exploit British military weaknesses during the First Anglo-Burmese War.

Dhal Revolt:

• The Dhal Revolt, considered the earliest tribal uprising in Jharkhand, broke out in 1767 under the leadership of Jagannath Dhal, the former ruler of Dhalbhum (now in West Bengal).
• The rebellion was sparked by resentment against the East India Company's growing influence, which displaced local power structures. The conflict endured for a decade, ending when the British reinstated Jagannath Dhal as the regional king in 1777 to pacify the unrest

 

Tana Bhagat Movement:

• Launched in 1914 by Jatra Bhagat, a prominent leader of the Oraon tribe, the Tana Bhagat movement aimed to restore indigenous values while rejecting British authority and Western cultural impositions. Focused on agrarian concerns, the movement called for refusal to pay taxes and urged laborers to resist forced or unfair work conditions

 

 

5. Birsa Munda and Janjatiya Gaurav Divas

 

• Birsa Munda holds a revered place in India’s freedom struggle as one of the most iconic tribal leaders who rose against British colonial rule and social injustice. Born on 15th November 1875 in the village of Ulihatu in present-day Jharkhand, Birsa belonged to the Munda tribe, an indigenous community of the Chotanagpur Plateau.
• He emerged as a powerful symbol of tribal resistance and social reform at a very young age and came to be known with deep respect as “Dharti Aba”, meaning “Father of the Earth”, for his deep connection with the land and the lives of his people.
• During the late 19th century, the British administration introduced exploitative land revenue systems and enabled the encroachment of tribal lands by non-tribal landlords and moneylenders.
• Alongside economic oppression, Christian missionaries sought to convert tribal populations, often undermining traditional tribal customs and beliefs. In this context of rising disenfranchisement, Birsa Munda led a major tribal uprising known as the “Ulgulan”, or the Great Tumult, which took place between 1899 and 1900.
• This movement, often referred to as the Munda Rebellion, was aimed at expelling the British from the region, ending the zamindari system, and restoring tribal land rights and autonomy.
• The Ulgulan was not merely a political revolt; it was also a social and spiritual movement. Birsa called upon his people to reject colonial laws, stop paying taxes, and embrace a purer way of life based on indigenous customs and his own vision of a just and egalitarian society, which he termed the “Birsa Raj”.
• He also preached against superstitions and promoted a moral code among his followers. His ideas quickly gained popularity, and thousands rallied behind him, making the movement one of the most organized tribal uprisings during colonial rule.
• However, the rebellion was short-lived. In March 1900, Birsa Munda was captured while asleep in the Jamkopai forest. He died under mysterious circumstances in Ranchi Jail on 9th June 1900, at the age of just 25.
• Despite his early death, his legacy endured, and he became a lasting symbol of tribal pride, resistance, and identity.
• In recognition of his immense contribution to India’s freedom struggle and the assertion of tribal rights, the Government of India declared 15th November, Birsa Munda’s birth anniversary, as “Janjatiya Gaurav Divas”.
• The day is observed across the country to celebrate and honour the valour, sacrifices, and contributions of tribal freedom fighters, not just Birsa Munda, but many others who stood up against colonial and feudal exploitation.
• It serves as a reminder of the unique and crucial role that tribal communities have played in shaping India’s history and preserving its cultural diversity

 

For Prelims: Paika rebellion, Santhal rebellion, important tribal uprisings   For Mains: GS I - Modern Indian History

 

Previous Year Questions   1.The Paika Rebellion was led by: (SSC JE CE 2019) A.Bakshi Jagabandhu B.Titu Mir C.Kanhu D.Sidhu Answer (A)

Source: Indianexpress