Sample CBSE Class 10 Science questions — pre-loaded

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1. Define the term 'refraction of light' and state Snell's law.
2. A resistor of 10Ω is connected to a 5V battery. Find the current flowing through the circuit. (Use Ohm's law)
3. What is the role of the ozone layer in protecting life on Earth?
4. If the focal length of a concave mirror is 15 cm, what is its radius of curvature?
5. Differentiate between renewable and non-renewable sources of energy with one example each.
6. State Newton's third law of motion with one everyday example.
7. Why does the sky appear blue during the day?
8. Define electric power. Write its SI unit and the formula relating it to V and I.
9. What is the difference between a 'group' and a 'period' in the modern periodic table?
10. Define a reflex action and give one example.
11. A force of 20 N moves an object through a distance of 5 m in the direction of the force. Calculate the work done.
12. Write the balanced chemical equation for photosynthesis.
13. State two main differences between alternating current (AC) and direct current (DC).
14. Define resistivity of a conductor. State its SI unit.
15. Distinguish between heredity and variation with one example each.

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Answer key & explanations

Quick answers with working for the sample questions above. Use this to self-check before generating a fresh AI mock test.

1. Q1: Refraction is the bending of light when it passes from one transparent medium to another due to a change in its speed. Snell's law: n₁ sin θ₁ = n₂ sin θ₂, i.e. the ratio sin i / sin r is constant for a given pair of media (the refractive index).
2. Q2: Using Ohm's law, I = V / R = 5 V / 10 Ω = 0.5 A. The current through the circuit is 0.5 ampere.
3. Q3: The ozone layer in the stratosphere absorbs most of the Sun's harmful ultraviolet (UV-B and UV-C) radiation, protecting living organisms from skin cancer, cataracts, damage to crops and harm to aquatic life.
4. Q4: For a spherical mirror, R = 2f. So R = 2 × 15 cm = 30 cm.
5. Q5: Renewable sources can be replenished naturally on a human timescale (e.g. solar energy). Non-renewable sources exist in finite reserves and exhaust with use (e.g. coal / petroleum).
6. Q6: To every action there is an equal and opposite reaction. Example: when you jump off a small boat onto a jetty, the boat moves backward as you push it forward.
7. Q7: Sunlight is scattered by the molecules of the atmosphere. Shorter wavelengths (blue) are scattered far more than longer wavelengths (red) — this is Rayleigh scattering — so the sky appears blue.
8. Q8: Electric power is the rate at which electrical energy is consumed (or work is done) in a circuit. SI unit: watt (W). Formula: P = V × I (also P = I²R = V²/R).
9. Q9: A 'group' is a vertical column (elements with similar chemical properties / same number of valence electrons). A 'period' is a horizontal row (elements with the same number of shells).
10. Q10: A reflex action is a quick, automatic response to a stimulus controlled by the spinal cord (not the brain). Example: pulling the hand back on touching a hot object.
11. Q11: Work done W = F × d × cos θ. Force and displacement are in the same direction (θ = 0°), so W = 20 × 5 × 1 = 100 J.
12. Q12: 6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂ (in the presence of sunlight and chlorophyll).
13. Q13: (i) AC reverses its direction periodically; DC flows in one direction only. (ii) AC can be stepped up/down by transformers and is used for transmission; DC is used in batteries and electronic devices.
14. Q14: Resistivity (ρ) is the resistance offered by a conductor of unit length and unit cross-sectional area at a given temperature. SI unit: ohm-metre (Ω·m).
15. Q15: Heredity = transmission of characters from parents to offspring (e.g. eye colour). Variation = differences seen between offspring and parents or among siblings (e.g. height differences in a family).

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