60 प्रश्न: 26 विकल्प, 20 लघु, 14 दीर्घ। प्रत्येक प्रश्न पर वर्ष टैग।
Which of the following is a combination reaction?
सही विकल्प: C — 2Mg + O2 → 2MgO
Two or more reactants join to form a single product. Magnesium burns in oxygen to give one product, magnesium oxide. / दो या अधिक अभिकारक मिलकर एक उत्पाद बनाते हैं। मैग्नीशियम ऑक्सीजन में जलकर केवल MgO देता है।
A solution with pH = 2 is best described as
सही विकल्प: B — Strongly acidic / प्रबल अम्लीय
The pH scale runs from 0 to 14. Values much below 7 are strongly acidic; pH 2 is typical of lemon juice or dilute HCl. / pH 7 से बहुत कम होना प्रबल अम्लीयता दर्शाता है।
Sodium metal is stored under kerosene because it
सही विकल्प: B — Reacts vigorously with air and moisture / वायु और नमी से तीव्र अभिक्रिया करता है
Sodium is highly reactive. Kerosene cuts off contact with oxygen and moisture, so the metal does not catch fire. / सोडियम अत्यंत क्रियाशील है; मिट्टी का तेल इसे वायु से बचाता है।
Two successive members of a homologous series differ by
सही विकल्प: B — CH2 / एक मेथिलीन समूह
Each next member of a homologous series has one extra CH2 unit and a mass increase of 14 u. / प्रत्येक अगले सदस्य में एक CH2 इकाई अधिक होती है।
The structural and functional unit of the human kidney is the
सही विकल्प: C — Nephron / नेफ्रॉन
Each kidney contains about a million nephrons that filter blood and form urine. / प्रत्येक वृक्क में लगभग दस लाख नेफ्रॉन होते हैं जो रक्त को छानते हैं।
The plant hormone that causes the shoot to bend towards light is
सही विकल्प: B — Auxin / ऑक्सिन
Auxin collects on the shaded side of the shoot, making those cells elongate so the tip bends towards light (phototropism). / ऑक्सिन छाया वाली ओर एकत्र होकर कोशिकाओं को लंबा करता है।
Binary fission is the usual mode of reproduction in
सही विकल्प: B — Amoeba / अमीबा
Amoeba divides its nucleus and cytoplasm into two equal daughter cells. Hydra buds; yeast buds; Spirogyra fragments. / अमीबा दो समान संतति कोशिकाओं में विभाजित होता है।
In humans, the sex of a child is decided by
सही विकल्प: B — The type of sperm (X or Y) that fertilises the egg / अंडाणु को निषेचित करने वाले शुक्राणु से
Eggs always carry X. A sperm may carry X (girl, XX) or Y (boy, XY). / अंडाणु में सदैव X होता है; X शुक्राणु से बालिका और Y से बालक जन्म लेता है।
The SI unit of power of a lens is the
सही विकल्प: B — Dioptre / डायोप्टर
Power P = 1/f (f in metres). One dioptre is the power of a lens of focal length 1 m. / क्षमता P = 1/f (f मीटर में); 1 डायोप्टर = 1 मीटर फोकस दूरी।
A person who can see nearby objects clearly but not distant ones suffers from
सही विकल्प: B — Myopia / निकटदृष्टि
In myopia the image of a distant object forms in front of the retina. A concave lens diverges rays so the image falls on the retina. / निकटदृष्टि में दूर की प्रतिबिंब रेटिना के आगे बनती है; अवतल लेंस से सुधार होता है।
A 6 Ω resistor carries a current of 2 A. The potential difference across it is
सही विकल्प: C — 12 V
Ohm's law: V = IR = 6 × 2 = 12 V. / ओम का नियम: V = IR = 6 × 2 = 12 V।
The device that converts mechanical energy into electrical energy is a
सही विकल्प: B — Electric generator / विद्युत जनित्र
A generator uses electromagnetic induction: a coil rotating in a magnetic field produces induced current. A motor does the reverse. / जनित्र में चुंबकीय क्षेत्र में कुंडली घूमने से प्रेरित धारा बनती है।
What is corrosion? Write one method to prevent rusting of iron.
Corrosion is the slow eating away of a metal by air, moisture or chemicals. Rusting of iron (hydrated Fe2O3) is the common example. Prevention: painting, oiling, galvanising (zinc coat), alloying (stainless steel) or sacrificial protection. / संक्षारण वायु, नमी या रसायनों द्वारा धातु का धीरे-धीरे क्षय है। लोहे पर जंग (जलयोजित Fe2O3) इसका उदाहरण है। बचाव: पेंट, तेल, जस्ते की परत (गैल्वेनीकरण), मिश्रधातु या बलिदानी सुरक्षा।
Why does tooth enamel start decaying when the pH in the mouth falls below 5.5? Name one substance that can restore pH.
Tooth enamel is calcium phosphate, which dissolves in a strongly acidic medium. Bacteria on leftover sugar produce acids and drop pH below 5.5. A basic toothpaste or milk of magnesia (Mg(OH)2) neutralises the acid and raises pH. / इनैमल कैल्शियम फॉस्फेट है जो प्रबल अम्ल में घुल जाता है। शर्करा पर बैक्टीरिया अम्ल बनाते हैं। क्षारीय टूथपेस्ट या मिल्क ऑफ मैग्नीशिया pH बढ़ाता है।
Give two differences between ionic and covalent compounds.
Ionic compounds (e.g. NaCl) have high melting points and conduct electricity in molten or aqueous state because ions can move. Covalent compounds (e.g. CH4, HCl gas) have low melting points and are generally poor conductors as they lack free ions or electrons. / आयनिक यौगिकों का गलनांक उच्च होता है और पिघली/जलीय अवस्था में वे विद्युत चालक हैं। सहसंयोजक यौगिकों का गलनांक निम्न होता है और वे प्रायः कुचालक होते हैं।
What is catenation? Why does carbon show this property strongly?
Catenation is the ability of an atom to form long chains or rings by bonding with other atoms of the same element. Carbon does this strongly because the C–C bond is stable and carbon is tetravalent (four covalent bonds), so a huge variety of chains, branches and rings is possible. / श्रृंखलन समान परमाणुओं से लंबी श्रृंखला/वलय बनाने का गुण है। C–C बंध स्थिर है और कार्बन चतुःसंयोजी है, अतः विविध संरचनाएँ बनती हैं।
Why is the blood going to the lungs from the heart called deoxygenated? How is it different after returning?
Blood in the right ventricle has given oxygen to body cells and picked up CO2, so it is deoxygenated. In the lungs, CO2 is released and O2 is absorbed; the left atrium then receives oxygenated blood, which the left ventricle pumps to the body (double circulation). / दाएँ निलय का रक्त कोशिकाओं को O2 दे चुका होता है। फेफड़ों में CO2 निकलती है और O2 जुड़ती है; बायाँ निलय इस ऑक्सीजनित रक्त को शरीर में भेजता है।
What is a reflex action? Trace the path of a reflex arc when you touch a hot utensil.
A reflex is a sudden, involuntary response that protects the body. Path: heat receptors in skin → sensory neuron → spinal cord (relay neuron) → motor neuron → arm muscles pull the hand away. The brain is informed later; the action itself is completed in the spinal cord. / प्रतिवर्त अचानक, अनैच्छिक रक्षा प्रतिक्रिया है। मार्ग: त्वचा के ग्राही → संवेदी न्यूरॉन → मेरुरज्जु → चालक न्यूरॉन → पेशियाँ हाथ हटाती हैं।
State two advantages of vegetative propagation in plants.
1. New plants are genetically identical to the parent, so useful traits (taste, yield, flower colour) are kept. 2. Plants that do not produce viable seeds (banana, rose, sugarcane) can still be multiplied quickly from stem, leaf or root. / 1. संतति जनक के समान गुण रखती है। 2. बिना बीज वाले पौधों (केला, गुलाब, गन्ना) को तना/पत्ती/जड़ से शीघ्र बढ़ाया जा सकता है।
An object is placed 30 cm in front of a convex lens of focal length 10 cm. Find the image distance and state the nature of the image.
Using the lens formula, v = +15 cm. The image is real, inverted and diminished, formed on the other side of the lens between F and 2F. / लेंस सूत्र से v = +15 सेमी। प्रतिबिंब वास्तविक, उलटा और छोटा है; लेंस के दूसरी ओर F और 2F के बीच बनता है।
Two resistors of 3 Ω and 6 Ω are connected in parallel. Calculate the equivalent resistance.
Equivalent resistance Rp = 2 Ω. The parallel combination is less than the smaller resistor, which is expected. / तुल्य प्रतिरोध 2 ओम है। समांतर संयोजन छोटे प्रतिरोध से भी कम होता है।
What are biodegradable and non-biodegradable wastes? Give one example of each.
Biodegradable wastes are broken down by microbes (vegetable peels, paper, cotton). Non-biodegradable wastes resist natural decay and stay in the environment (plastic bags, glass, many metals). They can enter food chains and cause biomagnification. / जैव-निम्नीकरणीय अपशिष्ट सूक्ष्मजीवों से सड़ते हैं (छिलके, कागज)। प्लास्टिक, काँच आदि नहीं सड़ते और खाद्य श्रृंखला में जमा हो सकते हैं।
Define a balanced chemical equation. Balance: Fe + H2O → Fe3O4 + H2. Name the type of reaction when a more reactive metal displaces a less reactive metal from its salt solution, with one example.
A balanced equation has the same number of atoms of each element on both sides (law of conservation of mass). Balanced form: 3Fe + 4H2O → Fe3O4 + 4H2 (steam on hot iron). A more reactive metal displacing a less reactive one is a displacement reaction, e.g. Zn + CuSO4 → ZnSO4 + Cu (blue solution fades as copper is deposited). Combination, decomposition, displacement and double displacement are the four types commonly tested. / संतुलित समीकरण में दोनों ओर प्रत्येक तत्व के परमाणु समान होते हैं। 3Fe + 4H2O → Fe3O4 + 4H2। विस्थापन: Zn + CuSO4 → ZnSO4 + Cu।
Describe the path of food in the human alimentary canal. Mention the role of bile and of villi.
Food is ingested through the mouth (teeth chew; saliva has amylase for starch). It is swallowed via the oesophagus by peristalsis into the stomach, where pepsin and HCl begin protein digestion. The partly digested mass enters the small intestine. The liver sends bile (no enzyme) which emulsifies fats into tiny droplets; the pancreas sends amylase, trypsin and lipase. Digested nutrients are absorbed by finger-like villi that increase surface area and have a rich blood supply. Undigested waste is stored in the large intestine (water absorbed) and egested through the anus. / मुँह → ग्रसनी → ग्रासनली → आमाशय → छोटी आँत → बड़ी आँत → मलद्वार। पित्त वसा का इमल्सीकरण करता है; रसांकुर अवशोषण सतह बढ़ाते हैं।
Draw a labelled outline (in words) of the human male and female reproductive systems. State the function of the testis, ovary and placenta.
Male: a pair of testes (in scrotum) produce sperms and testosterone; vas deferens carries sperms; prostate and seminal vesicles add fluid; urethra in the penis delivers semen. Female: a pair of ovaries release one egg each month and secrete oestrogen/progesterone; oviduct (fallopian tube) is the usual site of fertilisation; uterus holds the growing embryo; vagina receives sperms. The placenta is a disc of tissue between mother and foetus: it supplies oxygen and food, removes CO2 and wastes, and lets some antibodies pass, without mixing the two bloods. / नर: वृषण शुक्राणु व टेस्टोस्टेरॉन बनाते हैं। मादा: अंडाशय अंडाणु व हार्मोन छोड़ता है। प्लेसेंटा भ्रूण को पोषण-ऑक्सीजन देता है और अपशिष्ट हटाता है; रक्त मिश्रित नहीं होता।
A convex lens has power +5 D. An object is placed 30 cm from the lens. Calculate the focal length, the image distance and the magnification. State whether the image is real or virtual.
Focal length f = +20 cm. Image distance v = +60 cm. Magnification m = −2. The image is real, inverted and twice as large as the object, formed on the other side of the lens. / f = +20 सेमी, v = +60 सेमी, m = −2। प्रतिबिंब वास्तविक, उलटा और वस्तु से दोगुना है।
A 12 V battery is connected to two 4 Ω resistors in series. Calculate (i) total resistance (ii) current in the circuit (iii) voltage across each resistor (iv) power drawn from the battery. Five 100 W lamps are used 4 hours a day. Find energy used in 30 days if 1 kWh costs ₹6, also find the bill.
Series pair: R = 8 Ω, I = 1.5 A, 6 V across each resistor, power = 18 W. Five lamps for a month use 60 kWh; bill = ₹360. / श्रेणी में R = 8 ओम, I = 1.5 A, प्रत्येक पर 6 V, शक्ति 18 W। लैम्पों की मासिक ऊर्जा 60 kWh, बिल ₹360।
State Fleming's left-hand rule. How does an electric motor work? Also explain why CFCs damage the ozone layer and name one step taken to reduce this damage.
Fleming's left-hand rule (motor rule): stretch the thumb, forefinger and middle finger of the left hand mutually at right angles. Forefinger → magnetic field, middle finger → current, thumb → force on the conductor. In a motor, a current-carrying coil in a magnetic field experiences this force; a split-ring commutator reverses current every half rotation so the coil keeps turning and electrical energy becomes mechanical energy. CFCs from old refrigerators and aerosols rise to the stratosphere; UV light frees chlorine atoms that repeatedly destroy O3 molecules. The Montreal Protocol and use of safer refrigerants (HFCs/natural gases) have reduced CFC release. / वामहस्त: तर्जनी क्षेत्र, मध्यमा धारा, अंगूठा बल। मोटर में धारावाही कुंडली पर बल लगता है; विभक्त वलय से दिशा पलटती रहती है। CFC से क्लोरीन ओजोन तोड़ती है; मॉन्ट्रियल समझौते से CFC घटाए गए।
A wire of resistance 8 Ω carries a current of 0.5 A. The potential difference across its ends is
सही विकल्प: B — 4 V
Ohm's law: V = IR = 8 × 0.5 = 4 V. / ओम का नियम: V = IR = 4 V।
Three resistors of 6 Ω each are joined in series. The equivalent resistance is
सही विकल्प: D — 18 Ω
Series: Rs = R + R + R = 18 Ω. / श्रेणी में प्रतिरोध जुड़ते हैं: 6+6+6 = 18 ओम।
An electric heater of 1100 W is used on 220 V mains. The current drawn is
सही विकल्प: C — 5 A
P = VI ⇒ I = P/V = 1100/220 = 5 A. / शक्ति P = VI, अतः I = 5 A।
Heat produced in a 5 Ω resistor carrying 2 A for 2 minutes is
सही विकल्प: D — 2400 J
H = I²Rt = 4 × 5 × 120 = 2400 J. Time must be in seconds. / H = I²Rt; समय सेकंड में = 120 s।
The functional group present in CH3COOH is
सही विकल्प: C — Carboxylic acid (–COOH) / कार्बोक्सिलिक अम्ल
CH3COOH is ethanoic (acetic) acid; the –COOH group is the carboxylic acid group. / यह एथेनॉइक अम्ल है; –COOH कार्बोक्सिल समूह है।
Ethanol reacts with sodium metal to give
सही विकल्प: B — Sodium ethoxide and hydrogen / सोडियम एथॉक्साइड और हाइड्रोजन
2C2H5OH + 2Na → 2C2H5ONa + H2. The gas evolved burns with a pop. / सोडियम एथॉक्साइड तथा H2 गैस बनती है।
Soaps do not form lather easily in hard water because hard water contains
सही विकल्प: B — Ca2+ and Mg2+ ions that form scum / कैल्शियम व मैग्नीशियम आयन जो स्कम बनाते हैं
Calcium and magnesium salts of fatty acids are insoluble (scum). Detergents work better in hard water. / Ca/Mg के वसीय लवण अघुलनशील स्कम बनाते हैं।
In Mendel's monohybrid cross, the typical F2 phenotypic ratio is
सही विकल्प: C — 3 : 1
A tall × dwarf cross gives all tall F1; selfing F1 gives about 3 tall : 1 dwarf in F2. 9:3:3:1 is dihybrid. / F2 में लगभग 3 लंबा : 1 बौना। 9:3:3:1 द्विसंकर है।
A trait that a person develops by practice (for example, a scar or a trained skill) is
सही विकल्प: B — Acquired trait / उपार्जित गुण
Acquired traits do not change the DNA of germ cells, so they are not passed to children. / उपार्जित गुण जनन कोशिकाओं के DNA नहीं बदलते, अतः संतति में नहीं जाते।
Magnetic field lines around a current-carrying straight wire are
सही विकल्प: B — Concentric circles in a plane perpendicular to the wire / तार के लंब तल में संकेंद्री वृत्त
Iron filings form concentric circles. The right-hand thumb rule gives the direction. / लोहे का बुरादा संकेंद्री वृत्त बनाता है; दक्षिणावर्त/वामावर्त दिशा अंगूठे के नियम से मिलती है।
Magnetic field lines
सही विकल्प: B — Never intersect / कभी नहीं कटतीं
If two lines crossed, the field at that point would have two directions, which is impossible. Outside a bar magnet they go N → S. / कटने पर एक बिंदु पर दो दिशाएँ हो जातीं, जो असंभव है।
The main combustible gas in biogas is
सही विकल्प: B — Methane / मीथेन
Biogas is roughly 50–70% methane (CH4), which burns to give heat for cooking. CO2 is present but does not burn. / बायोगैस में लगभग आधी-दो तिहाई मीथेन होती है जो जलती है।
Which of the following is a non-conventional (renewable) source of energy?
सही विकल्प: C — Wind energy / पवन ऊर्जा
Wind, sun, biogas and falling water can be replenished. Coal, petroleum and natural gas are fossil fuels that take millions of years to form. / पवन, सूर्य, बायोगैस नवीकरणीय हैं; कोयला-पेट्रोल जीवाश्म ईंधन हैं।
The SI unit of electrical resistivity is
सही विकल्प: B — Ohm-metre / ओम-मीटर
From R = ρ l / A, ρ = R A / l, so unit is Ω m. Resistivity is a material property; resistance depends on length and area too. / R = ρl/A से ρ का मात्रक ओम-मीटर है।
Resistors of 2 Ω, 3 Ω and 5 Ω are connected in series to a 10 V battery. Find the current in the circuit and the voltage across the 5 Ω resistor.
I = 1 A; voltage across 5 Ω = 5 V. / धारा 1 A, 5 ओम पर 5 V।
What happens when ethanol is heated with excess concentrated H2SO4 at 170°C? Write the balanced equation and name the reaction.
Ethene and water are formed (dehydration). C2H5OH → C2H4 + H2O (conc. H2SO4, 170°C). / निर्जलन से एथीन और जल बनते हैं।
Distinguish between acquired and inherited traits with one example of each.
Inherited traits are coded in DNA and come from parents (blood group, attached ear lobes, seed colour in pea). Acquired traits develop in one lifetime by use, injury or learning (a wrestler's muscles, a cut on the finger, speaking a language) and are not passed through gametes. / वंशानुगत गुण DNA में होते हैं (रक्त समूह)। उपार्जित गुण जीवन में बनते हैं और संतति में नहीं जाते।
State two properties of magnetic field lines. Why can two field lines never cross?
They emerge from the north pole and enter the south pole outside a magnet; they are closer where the field is stronger. If two lines crossed, a compass at that point would have to point in two directions at once, which cannot happen. / रेखाएँ बाहर N से S जाती हैं, सघनता अधिक क्षेत्र दर्शाती है; कटने पर एक बिंदु पर दो दिशाएँ असंभव हैं।
Give two advantages of using solar energy. Mention one limitation.
It is renewable and does not produce smoke or greenhouse gases at the point of use. A limitation: it is not available at night or on heavily cloudy days, and the initial cost of panels is high. / नवीकरणीय और स्वच्छ; रात/बादल में उपलब्ध नहीं तथा पैनल महँगे।
Define electrical resistivity. On what factors does the resistance of a wire depend?
Resistivity ρ is the resistance of a conductor of unit length and unit cross-section (a material constant at a given temperature). Resistance R = ρ l / A, so it increases with length, decreases with area, and depends on the metal and temperature. / प्रतिरोधकता पदार्थ का गुण है। R लंबाई से बढ़ता, क्षेत्रफल से घटता है।
Explain the cleansing action of soap in brief.
A soap molecule has a hydrophobic hydrocarbon tail that dissolves in oil/dirt and a hydrophilic –COONa head that dissolves in water. In water the molecules form micelles that trap grease inside; rinsing washes the micelles away. / पूँछ तेल में, सिरा जल में घुलता है; माइसेल मैल को घेरकर धुल जाते हैं।
A couple has two daughters. The husband says the wife is “responsible” for not having a son. Use sex-chromosome facts to correct him.
The mother's egg always carries X. The father's sperm carries either X (daughter, XX) or Y (son, XY). So the sex of each child is decided by which sperm fertilises the egg, not by the mother. Having two daughters is chance, not a fault. / अंडाणु में सदैव X होता है; X या Y शुक्राणु से लिंग तय होता है — दोष पत्नी का नहीं।
How does a current-carrying solenoid behave like a bar magnet? State one use of this fact.
Field lines inside a solenoid are nearly parallel (uniform field) and outside they look like those of a bar magnet, with a north and a south face given by the clock-face / right-hand rule. A soft-iron core makes a strong electromagnet used in electric bells, cranes and relays. / भीतर क्षेत्र लगभग समान; सिरे N-S जैसे। नरम लोहे से विद्युत चुंबक बनता है।
Why must we conserve fossil fuels? Give two reasons.
They are formed over millions of years and will run out if used at the present rate (non-renewable). Burning them also releases CO2, SO2 and smoke that cause climate change and air pollution. Saving fuel and shifting to biogas, sun and wind reduces both shortages and pollution. / बनने में युग लगते हैं और जलाने से प्रदूषण/जलवायु परिवर्तन होता है।
A 6 Ω resistor and a 3 Ω resistor are connected in parallel. This combination is then joined in series with a 4 Ω resistor to a 12 V battery. Calculate (i) equivalent resistance of the parallel pair (ii) total resistance (iii) current from the battery (iv) current through the 3 Ω resistor.
Rp = 2 Ω; Rtotal = 6 Ω; I = 2 A; current in 3 Ω = 4/3 A. / समांतर 2 ओम, कुल 6 ओम, कुल धारा 2 A, 3 ओम में 4/3 A।
What is a homologous series? Write the next two members after CH4 and C2H6. Give two chemical properties of ethanol and one use of ethanoic acid.
A homologous series is a family of compounds with the same functional group and a CH2 difference between neighbours (alkanes: CnH2n+2). Next members: C3H8 (propane), C4H10 (butane). Ethanol: burns to CO2 + H2O; with Na gives H2; with conc. H2SO4 at 170°C gives ethene. Ethanoic acid is used in vinegar for food and as a starting chemical. / समाश्रय: समान क्रियात्मक समूह, अंतर CH2। अगले: प्रोपेन, ब्यूटेन। एथेनॉल जलता है / Na से H2 देता है। सिरका = तनु एथेनॉइक अम्ल।
Explain Mendel's monohybrid cross for tall and dwarf pea plants. How is the sex of a child determined in humans?
Pure tall (TT) × dwarf (tt) gives F1 all Tt (tall), showing dominance of T. Selfing F1 gives F2 genotypes TT : Tt : tt = 1 : 2 : 1 and phenotypes about 3 tall : 1 dwarf. In humans, eggs carry X; sperms carry X or Y in roughly equal numbers. XX is female, XY is male. The father's sperm decides the sex of that child. / F1 सब लंबे (Tt); F2 में 3:1। अंडाणु X, शुक्राणु X या Y — XY बालक, XX बालिका।
State Fleming's right-hand rule. How does an electric generator differ from an electric motor? Also state the rule that gives the direction of the magnetic field around a straight current-carrying wire.
Right-hand rule (generator): thumb → motion of conductor, forefinger → field, middle finger → induced current (all mutually perpendicular). A generator converts mechanical energy to electrical energy by electromagnetic induction; a motor converts electrical energy to mechanical energy (Fleming's left-hand rule). For a straight wire, the right-hand thumb rule: thumb along current, curled fingers show field circles. / दक्षिण-हस्त: अंगूठा गति, तर्जनी क्षेत्र, मध्यमा प्रेरित धारा। जनित्र यांत्रिक→विद्युत; मोटर उलटा। तार के लिए अंगूठा धारा, अंगुलियाँ वृत्त।
Distinguish between conventional and non-conventional sources of energy with two examples each. Describe the working of a biogas plant in brief.
Conventional: coal, petroleum, natural gas — limited, polluting fossil fuels. Non-conventional: solar, wind, biogas, tidal — renewable and cleaner. In a biogas plant, cattle dung and water slurry ferment anaerobically in a closed digester; methane-rich gas is collected in a dome for cooking/lighting and the leftover slurry is a nitrogen-rich manure. / पारंपरिक: कोयला-पेट्रोल। गैर-पारंपरिक: सूर्य-पवन-बायोगैस। गोबर-जल का अवायवीय किण्वन → मीथेन + खाद।
A 220 V, 100 W bulb is used 5 hours a day for 30 days. Calculate (i) current drawn by the bulb (ii) resistance of the filament (iii) energy consumed in kWh (iv) the bill if 1 kWh costs ₹8.
I = 5/11 A; R = 484 Ω; energy = 15 kWh; bill = ₹120. / धारा 5/11 A, R = 484 ओम, ऊर्जा 15 kWh, बिल ₹120।
Why does carbon form a large number of compounds? Draw the electron-dot structures of methane and ethene (describe them in words if needed). Distinguish saturated and unsaturated hydrocarbons.
Carbon is tetravalent and shows strong catenation (stable C–C bonds), so chains, branches and rings form. Methane: C with four shared pairs to four H atoms. Ethene: two C atoms share two pairs (C=C) and each also bonds to two H. Saturated hydrocarbons have only single C–C bonds (alkanes); unsaturated have double or triple bonds (alkenes, alkynes) and decolourise bromine water. / कार्बन चतुःसंयोजी है और श्रृंखलन करता है। मेथेन में चार एकल बंध; एथीन में C=C. संतृप्त = केवल एकल बंध; असंतृप्त = द्वि/त्रि बंध।
What is the heating effect of electric current? State Joule's law. A 4 Ω resistor carries 3 A for 5 minutes. Calculate the heat produced. Also mention one safety device based on this effect.
When current flows in a resistor, electrical energy becomes heat (H = I²Rt). For the given values H = 9 × 4 × 300 = 10800 J. A fuse (or MCB) melts / trips when excess current heats a thin wire, breaking the circuit. / धारा से प्रतिरोधक गर्म होता है। H = 10800 J. फ्यूज इसी ऊष्मा से पिघलकर परिपथ काटता है।
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