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BCSE (Class X) study materials
BCSE (Class X) study resources

BCSE (Class X) practice questions

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Question 1General (subject domains not enumerated in source)

Which of the following is the SI unit of electric current?

  1. Volt
  2. Watt
  3. Ohm
  4. Ampere Correct answer.

Explanation

The ampere is the base SI unit that measures the rate of flow of electric charge through a conductor. The volt measures potential difference, the ohm measures resistance, and the watt measures power, so none of these measure current itself.

Question 2General (subject domains not enumerated in source)

The chemical formula of common table salt is:

  1. NaCl Correct answer.
  2. CaCO3
  3. NaHCO3
  4. KCl

Explanation

Table salt is sodium chloride, formed from sodium and chlorine ions in a one-to-one ratio, giving the formula NaCl. Potassium chloride tastes salty but is a different compound, while calcium carbonate and sodium bicarbonate are chalk and baking soda respectively.

Question 3General (subject domains not enumerated in source)

Which organelle is known as the powerhouse of the cell because it produces most of the cell's energy?

  1. Ribosome
  2. Mitochondrion Correct answer.
  3. Golgi apparatus
  4. Nucleus

Explanation

Mitochondria carry out aerobic respiration, converting glucose and oxygen into ATP, the cell's usable energy currency. Ribosomes build proteins, the nucleus stores genetic material, and the Golgi apparatus packages and modifies proteins, so none of them generate energy on this scale.

Question 4General (subject domains not enumerated in source)

What is the value of the expression 3 + 4 × 2 according to the order of operations?

  1. 11 Correct answer.
  2. 10
  3. 24
  4. 14

Explanation

Multiplication is performed before addition, so 4 × 2 equals 8, and adding 3 gives 11. Working strictly left to right would wrongly give 14, which ignores the precedence of multiplication over addition.

Question 5General (subject domains not enumerated in source)

Which gas makes up the largest proportion of Earth's atmosphere?

  1. Argon
  2. Carbon dioxide
  3. Nitrogen Correct answer.
  4. Oxygen

Explanation

Nitrogen accounts for roughly 78 percent of the atmosphere by volume, making it the most abundant gas. Oxygen is second at about 21 percent, while carbon dioxide and argon are present only in small trace amounts.

Question 6General (subject domains not enumerated in source)

A train travels 180 kilometres in 3 hours. What is its average speed?

  1. 45 km/h
  2. 540 km/h
  3. 90 km/h
  4. 60 km/h Correct answer.

Explanation

Average speed equals total distance divided by total time, so 180 kilometres divided by 3 hours gives 60 km/h. Multiplying distance by time instead of dividing would produce a much larger and incorrect value.

Question 7General (subject domains not enumerated in source)

Which of these is a renewable source of energy?

  1. Coal
  2. Wind Correct answer.
  3. Petroleum
  4. Natural gas

Explanation

Wind energy is replenished naturally and will not run out on human timescales, so it is renewable. Coal, petroleum, and natural gas are fossil fuels formed over millions of years and are consumed faster than they form.

Question 8General (subject domains not enumerated in source)

In a right-angled triangle, the side opposite the right angle is called the:

  1. Hypotenuse Correct answer.
  2. Median
  3. Altitude
  4. Bisector

Explanation

The hypotenuse is by definition the side opposite the right angle and is always the longest side of a right-angled triangle. An altitude is a perpendicular drawn to a base, a median joins a vertex to the midpoint of the opposite side, and a bisector divides an angle or side into two equal parts.

Question 9General (subject domains not enumerated in source)

Which of the following is the correct order of taxonomic ranks from largest to smallest?

  1. Species, Genus, Family, Order, Class, Phylum, Kingdom
  2. Kingdom, Phylum, Class, Order, Family, Genus, Species Correct answer.
  3. Phylum, Kingdom, Order, Class, Genus, Family, Species
  4. Kingdom, Class, Phylum, Family, Order, Genus, Species

Explanation

The standard hierarchy runs kingdom, phylum, class, order, family, genus, and species, with each rank containing fewer organisms than the one before it. Species is the smallest and most specific rank, while kingdom is the broadest of these categories.

Question 10General (subject domains not enumerated in source)

Which property of metals allows them to be drawn into thin wires?

  1. Ductility Correct answer.
  2. Brittleness
  3. Sonority
  4. Malleability

Explanation

Ductility is the ability of a material to be stretched into wires without breaking, a characteristic property of metals such as copper. Malleability refers to being hammered into sheets, brittleness describes shattering under stress, and sonority is the ringing sound produced when struck.

Question 11General (subject domains not enumerated in source)

A number is increased by 20 percent and the result is 96. What was the original number?

  1. 80 Correct answer.
  2. 120
  3. 76.8
  4. 116

Explanation

If the original number is x, then 1.2x equals 96, so x equals 96 divided by 1.2, which is 80. Taking 20 percent of 96 and subtracting it would wrongly treat the increased value as the base.

Question 12General (subject domains not enumerated in source)

Which part of the human eye controls the amount of light entering it by changing the size of the pupil?

  1. Cornea
  2. Retina
  3. Iris Correct answer.
  4. Optic nerve

Explanation

The iris is the coloured muscular ring that contracts or relaxes to change the pupil's diameter, regulating light intake. The cornea refracts light, the retina contains light-sensitive cells, and the optic nerve carries signals to the brain.

Question 13General (subject domains not enumerated in source)

Which of the following equations represents a neutralisation reaction?

  1. Metal + acid → salt + hydrogen
  2. Salt + salt → two new salts
  3. Acid + base → salt + water Correct answer.
  4. Metal + oxygen → metal oxide

Explanation

Neutralisation occurs when an acid reacts with a base to form a salt and water, bringing the pH towards neutral. The reaction of a metal with an acid produces hydrogen gas, and a metal with oxygen produces an oxide, neither of which is neutralisation.

Question 14General (subject domains not enumerated in source)

A body moves with uniform velocity along a straight line. Which statement about the forces acting on it is correct?

  1. The net force acting on it is zero. Correct answer.
  2. A constant forward force acts on it.
  3. Its acceleration is increasing steadily.
  4. The forces on it are unbalanced.

Explanation

Uniform velocity means both speed and direction are constant, so acceleration is zero. By Newton's first law, a body with zero acceleration has zero net force, meaning all forces acting on it balance.

Question 15General (subject domains not enumerated in source)

Which of the following is a primary function of the roots of a plant?

  1. Producing seeds
  2. Carrying out photosynthesis
  3. Transporting food to the leaves
  4. Absorbing water and minerals Correct answer.

Explanation

Roots anchor the plant and absorb water and dissolved mineral salts from the soil through root hairs. Photosynthesis occurs mainly in leaves, seeds are produced by flowers, and food is transported from leaves through the phloem.

Question 16General (subject domains not enumerated in source)

What is the least common multiple of 12 and 18?

  1. 72
  2. 6
  3. 216
  4. 36 Correct answer.

Explanation

Prime factorising gives 12 = 2² × 3 and 18 = 2 × 3², so the LCM takes the highest power of each prime: 2² × 3² = 36. The value 6 is the greatest common divisor, not the multiple.

Question 17General (subject domains not enumerated in source)

Which process in the water cycle converts water vapour directly into liquid droplets in the atmosphere?

  1. Infiltration
  2. Evaporation
  3. Transpiration
  4. Condensation Correct answer.

Explanation

Condensation is the change of state from vapour to liquid, which occurs when moist air cools and forms cloud droplets. Evaporation and transpiration add vapour to the air, while infiltration is water soaking into the ground.

Question 18General (subject domains not enumerated in source)

A shopkeeper marks an item at 500 and offers a discount of 15 percent. What is the selling price?

  1. 435
  2. 485
  3. 450
  4. 425 Correct answer.

Explanation

A 15 percent discount on 500 is 75, so the selling price is 500 minus 75, which equals 425. Subtracting only 10 percent or 13 percent would give the other listed values, which do not match the stated discount.

Question 19General (subject domains not enumerated in source)

Which of the following best explains why a clinical thermometer has a narrow constriction just above the bulb?

  1. It prevents the mercury from rising too quickly.
  2. It reduces the amount of mercury needed for the reading.
  3. It stops the mercury from falling back when removed from the body. Correct answer.
  4. It allows the thermometer to measure higher temperatures.

Explanation

The constriction acts as a one-way valve: expanding mercury pushes past it, but on cooling the thread breaks at the narrow point so the reading is retained until shaken down. This lets a doctor read the temperature after the thermometer is taken out of the patient's mouth.

Question 20General (subject domains not enumerated in source)

Which of the following statements about sound waves is correct?

  1. They can travel through a vacuum.
  2. They travel faster in gases than in solids.
  3. Their speed is independent of the medium.
  4. They require a material medium to propagate. Correct answer.

Explanation

Sound is a mechanical wave and needs a material medium such as air, water, or steel to travel through, so it cannot cross a vacuum. It travels fastest in solids and slowest in gases, meaning its speed depends strongly on the medium.

Question 21General (subject domains not enumerated in source)

Which of the following is an example of a chemical change rather than a physical change?

  1. Rusting of iron Correct answer.
  2. Breaking of glass
  3. Melting of ice
  4. Dissolving sugar in water

Explanation

Rusting forms a new substance, hydrated iron oxide, and is not easily reversed, which identifies a chemical change. Melting, dissolving, and breaking only alter the physical state or size of the material without creating new substances.

Question 22General (subject domains not enumerated in source)

A car accelerates uniformly from rest to 20 m/s in 5 seconds. What distance does it cover in this time?

  1. 200 m
  2. 100 m
  3. 50 m Correct answer.
  4. 4 m

Explanation

Using s = ut + ½at² with u = 0 and a = 20/5 = 4 m/s², the distance is ½ × 4 × 25 = 50 m. Multiplying speed by time without accounting for the average speed during acceleration would give an incorrect larger value.

Question 23General (subject domains not enumerated in source)

In a class, the ratio of boys to girls is 3:2. If 10 more girls join, the ratio becomes 1:1. How many boys are in the class?

  1. 24
  2. 30 Correct answer.
  3. 20
  4. 36

Explanation

Let boys be 3k and girls 2k. After 10 girls join, 3k = 2k + 10, so k = 10 and boys equal 3 × 10 = 30. Substituting other values fails to satisfy the equality condition after the new girls join.

Question 24General (subject domains not enumerated in source)

An object is placed between the pole and the principal focus of a concave mirror. Which type of image is formed?

  1. Virtual, erect, and diminished
  2. Real, inverted, and enlarged
  3. Real, inverted, and diminished
  4. Virtual, erect, and enlarged Correct answer.

Explanation

When the object lies between the pole and focus of a concave mirror, the reflected rays diverge and form a virtual, erect, and magnified image behind the mirror. Real inverted images arise only when the object is beyond the principal focus.

Question 25General (subject domains not enumerated in source)

Equal masses of two metals, with specific heat capacities in the ratio 1:2, absorb equal amounts of heat. What is the ratio of their temperature rises?

  1. 4:1
  2. 1:4
  3. 2:1 Correct answer.
  4. 1:2

Explanation

Heat absorbed equals mass times specific heat capacity times temperature rise, so for equal heat and mass the temperature rise is inversely proportional to specific heat capacity. A capacity ratio of 1:2 therefore gives a temperature rise ratio of 2:1.

Question 26General (subject domains not enumerated in source)

Which of the following is the chemical formula of common table salt?

  1. CaCO3
  2. KCl
  3. NaHCO3
  4. NaCl Correct answer.

Explanation

Table salt is sodium chloride, an ionic compound made of sodium cations and chloride anions in a 1:1 ratio, giving the formula NaCl. Potassium chloride is a different salt, calcium carbonate is limestone or chalk, and sodium bicarbonate is baking soda.

Question 27General (subject domains not enumerated in source)

Which of the following is the largest gland in the human body?

  1. Liver Correct answer.
  2. Salivary gland
  3. Thyroid
  4. Pancreas

Explanation

The liver is the largest internal gland, weighing about 1.5 kg in an adult, and it performs many metabolic functions including bile production. The pancreas, thyroid, and salivary glands are all much smaller glands with more specific secretory roles.

Question 28General (subject domains not enumerated in source)

Which of the following numbers is a prime number?

  1. 21
  2. 29 Correct answer.
  3. 33
  4. 27

Explanation

A prime number has exactly two distinct positive factors: 1 and itself. The number 29 is not divisible by any integer other than 1 and 29, whereas 21, 27, and 33 are all divisible by 3, so they are composite.

Question 29General (subject domains not enumerated in source)

Which of the following is the main greenhouse gas released by the burning of fossil fuels?

  1. Oxygen
  2. Carbon dioxide Correct answer.
  3. Nitrogen
  4. Argon

Explanation

Burning coal, oil, and natural gas combines carbon with oxygen to form carbon dioxide, which traps heat in the atmosphere. Oxygen, nitrogen, and argon are not produced in large amounts by combustion and do not act as significant greenhouse gases.

Question 30General (subject domains not enumerated in source)

Which of the following is the value of 2 raised to the power 5?

  1. 25
  2. 10
  3. 32 Correct answer.
  4. 16

Explanation

The expression 2^5 means multiplying five factors of 2: 2 × 2 × 2 × 2 × 2, which equals 32. Multiplying the base by the exponent gives 10, squaring gives 25, and 2^4 gives 16, so these are common errors.

Question 31General (subject domains not enumerated in source)

Which of the following is the chief ore of aluminium?

  1. Galena
  2. Cinnabar
  3. Haematite
  4. Bauxite Correct answer.

Explanation

Bauxite is the principal aluminium ore, consisting mainly of hydrated aluminium oxides from which aluminium is extracted by electrolysis. Haematite is an iron ore, galena is a lead ore, and cinnabar is a mercury ore.

Question 32General (subject domains not enumerated in source)

Which of the following fractions is equivalent to 0.75?

  1. 4/5
  2. 7/10
  3. 2/3
  4. 3/4 Correct answer.

Explanation

To convert 0.75 to a fraction, write it as 75/100 and divide numerator and denominator by 25, giving 3/4. The other fractions have decimal values 0.666..., 0.8, and 0.7, which are not equal to 0.75.

Question 33General (subject domains not enumerated in source)

A car of mass 800 kg is moving at 15 m/s. Calculate its kinetic energy.

  1. 90,000 J Correct answer.
  2. 6,000 J
  3. 180,000 J
  4. 12,000 J

Explanation

Kinetic energy is given by the formula KE = ½mv². Substituting m = 800 kg and v = 15 m/s gives ½ × 800 × 225 = 90,000 J. Using mv instead of ½mv², or forgetting to square the speed, leads to the other values.

Question 34General (subject domains not enumerated in source)

Which of the following is the main function of haemoglobin in the blood?

  1. Production of bile
  2. Clotting of blood
  3. Defence against pathogens
  4. Transport of oxygen Correct answer.

Explanation

Haemoglobin is the iron-containing pigment in red blood cells that binds oxygen in the lungs and releases it in the tissues. Clotting is carried out by platelets and fibrin, defence by white blood cells, and bile is produced by the liver.

Question 35General (subject domains not enumerated in source)

A sum of money becomes 1,500 in 2 years at 10% per annum simple interest. What was the principal?

  1. 1,350
  2. 1,300
  3. 1,250 Correct answer.
  4. 1,200

Explanation

For simple interest, amount = principal × (1 + rt). Here 1,500 = P × (1 + 0.10 × 2) = 1.2P, so P = 1,500 ÷ 1.2 = 1,250. The other options do not satisfy the given amount after two years.

Question 36General (subject domains not enumerated in source)

Which of the following statements about the refraction of light is correct?

  1. Light does not change direction when it enters glass at an angle.
  2. Light bends away from the normal when it passes from air into glass.
  3. Light bends towards the normal when it passes from air into glass. Correct answer.
  4. The speed of light increases when it enters glass from air.

Explanation

Refraction occurs because light travels more slowly in an optically denser medium such as glass than in air. When a ray enters a denser medium at an angle, it bends towards the normal; the reverse happens on leaving the denser medium.

Question 37General (subject domains not enumerated in source)

Which of the following is the correct order of the first four stages of the human digestive process?

  1. Ingestion, absorption, digestion, egestion
  2. Absorption, ingestion, digestion, egestion
  3. Digestion, ingestion, absorption, egestion
  4. Ingestion, digestion, absorption, egestion Correct answer.

Explanation

Digestion begins with ingestion, the intake of food, followed by digestion, the breakdown of food into simpler substances. The products are then absorbed into the blood, and the undigested residue is removed by egestion.

Question 38General (subject domains not enumerated in source)

A shopkeeper sells an article for 450, making a profit of 12.5%. What was the cost price of the article?

  1. 400 Correct answer.
  2. 420
  3. 380
  4. 390

Explanation

Selling price equals cost price multiplied by 1 plus the profit rate. Here 450 = CP × 1.125, so CP = 450 ÷ 1.125 = 400. The other values do not give a 12.5% profit when increased by that percentage.

Question 39General (subject domains not enumerated in source)

Which of the following is the correct electronic configuration of a chlorine atom (atomic number 17)?

  1. 2, 8, 7 Correct answer.
  2. 2, 8, 8
  3. 2, 8, 5
  4. 2, 7, 8

Explanation

The K shell holds a maximum of 2 electrons and the L shell a maximum of 8, leaving 7 electrons in the M shell for chlorine. A configuration of 2, 8, 8 would correspond to argon, and the other arrangements violate the filling order.

Question 40General (subject domains not enumerated in source)

A student adds dilute hydrochloric acid to sodium carbonate. Which gas is produced?

  1. Carbon dioxide Correct answer.
  2. Oxygen
  3. Hydrogen
  4. Chlorine

Explanation

An acid reacts with a carbonate to form a salt, water, and carbon dioxide, which fizzes and turns limewater milky. Hydrogen is produced when an acid reacts with a metal, not a carbonate, and oxygen and chlorine are not products of this reaction.

Question 41General (subject domains not enumerated in source)

A wire of resistance 8 Ω is stretched uniformly so that its length is doubled. Assuming its volume remains constant, what is its new resistance?

  1. 8 Ω
  2. 4 Ω
  3. 32 Ω Correct answer.
  4. 16 Ω

Explanation

When a wire is stretched to double its length at constant volume, its cross-sectional area halves. Resistance is proportional to length and inversely proportional to area, so doubling the length and halving the area multiplies the resistance by four, giving 32 Ω.

Question 42General (subject domains not enumerated in source)

Which of the following is the correct IUPAC name of the compound CH3–CH2–OH?

  1. Ethanal
  2. Ethanol Correct answer.
  3. Methanol
  4. Ethanoic acid

Explanation

The compound has two carbon atoms and an –OH functional group, so its IUPAC name is ethanol. Methanol has one carbon, ethanal is an aldehyde, and ethanoic acid contains a carboxyl group.

Question 43General (subject domains not enumerated in source)

A man walks 3 km east, then 4 km north. What is his displacement from the starting point?

  1. 5 km Correct answer.
  2. 25 km
  3. 1 km
  4. 7 km

Explanation

The two legs are perpendicular, so displacement is the hypotenuse of a right triangle with sides 3 km and 4 km. By Pythagoras' theorem, displacement = √(3² + 4²) = √25 = 5 km.

Question 44General (subject domains not enumerated in source)

Which of the following statements about the magnetic field lines around a straight current-carrying conductor is correct?

  1. They form straight lines perpendicular to the conductor.
  2. They form concentric circles around the conductor. Correct answer.
  3. They run parallel to the conductor.
  4. They radiate outward from the conductor like spokes.

Explanation

The magnetic field around a long straight current-carrying wire consists of concentric circular field lines in a plane perpendicular to the wire. The direction of these circles is given by the right-hand thumb rule, and they do not run parallel or radially outward.

Question 45General (subject domains not enumerated in source)

Which of the following is the main reason why a fuse is connected in series with an electrical appliance?

  1. To melt and break the circuit when the current exceeds a safe value Correct answer.
  2. To convert alternating current into direct current
  3. To store electrical energy for later use
  4. To increase the current flowing through the appliance

Explanation

A fuse contains a thin wire of low melting point that heats up and melts when the current exceeds its rated value, thereby breaking the circuit and protecting the appliance from damage. It does not boost current, store energy, or rectify current.

Question 46General (subject domains not enumerated in source)

A cone has a base radius of 7 cm and a height of 24 cm. What is its slant height?

  1. 17 cm
  2. 23 cm
  3. 31 cm
  4. 25 cm Correct answer.

Explanation

The slant height l of a cone is related to radius r and height h by l² = r² + h². Here l² = 7² + 24² = 49 + 576 = 625, so l = 25 cm.

Question 47General (subject domains not enumerated in source)

A student observes that a ray of light passing through a rectangular glass slab emerges parallel to its original direction but shifted sideways. Which phenomenon explains this?

  1. Total internal reflection
  2. Diffraction of light
  3. Dispersion of light
  4. Refraction at two parallel surfaces Correct answer.

Explanation

The ray bends towards the normal on entering the glass and away from the normal on leaving, and because the two surfaces are parallel the emergent ray is parallel to the incident ray but laterally displaced. Total internal reflection, dispersion, and diffraction do not describe this parallel shift.

Question 48General (subject domains not enumerated in source)

Which of the following statements about the reaction between hydrogen and oxygen to form water is correct?

  1. It is a decomposition reaction that absorbs energy.
  2. It is a combination reaction that releases energy. Correct answer.
  3. It is a displacement reaction that produces a gas.
  4. It is a double displacement reaction that forms a precipitate.

Explanation

Two substances, hydrogen and oxygen, combine to form a single product, water, so the reaction is a combination reaction. The formation of water from its elements releases a large amount of energy, which is why hydrogen is used as a fuel.

Question 49General (subject domains not enumerated in source)

A body is thrown vertically upwards with a velocity of 20 m/s. Taking g = 10 m/s², what is the maximum height reached?

  1. 10 m
  2. 40 m
  3. 2 m
  4. 20 m Correct answer.

Explanation

At the highest point the final velocity is zero. Using v² = u² – 2gh gives 0 = 400 – 20h, so h = 20 m. The other values arise from misusing the formula or from confusing time with height.

Question 50General (subject domains not enumerated in source)

In a certain code, if CAT is written as 3-1-20, how is DOG written in the same code?

  1. 4-15-7 Correct answer.
  2. 4-14-7
  3. 3-15-7
  4. 4-15-6

Explanation

The code replaces each letter by its position in the alphabet: C = 3, A = 1, T = 20. Applying the same rule, D = 4, O = 15, and G = 7, giving 4-15-7.