CBSE Class 11 Physics Flashcards

24 sample cards from the Physics deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. How does g vary with height h above and depth d below Earth's surface?

   At height: g_h = g(1 − 2h/R) for small h. At depth: g_d = g(1 − d/R). g decreases both above the surface and below it (zero at the centre).

2. Define stress and strain, and state Hooke's law.

   Stress = force per unit area (N/m²); strain = fractional deformation (dimensionless). Hooke's law: within the elastic limit, stress ∝ strain, i.e., stress = (modulus of elasticity) × strain.

3. Define Young's modulus.

   Y = longitudinal stress / longitudinal strain = (F/A)/(ΔL/L). It measures a material's resistance to length change under tension/compression.

4. Differentiate between elastic limit, yield point, and breaking point on a stress–strain curve.

   Elastic limit: maximum stress for which the body returns to original shape. Yield point: stress beyond which permanent (plastic) deformation begins. Breaking point: stress at which the material fractures.

5. State Pascal's law.

   Pressure applied to an enclosed fluid is transmitted undiminished to every part of the fluid and the walls of the container. It is the basis of hydraulic systems.

6. State Archimedes' principle.

   A body wholly or partly immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced.

7. State Bernoulli's principle (equation) for steady, incompressible, non-viscous flow.

   P + ½ρv² + ρgh = constant along a streamline. Faster-moving fluid has lower pressure.

8. Define surface tension and viscosity.

   Surface tension is the force per unit length acting along a liquid surface (tends to minimize surface area), unit N/m. Viscosity is the internal friction opposing relative motion between fluid layers, unit Pa·s.

9. State the equation of continuity for fluid flow.

   A₁v₁ = A₂v₂ (Av = constant): for incompressible flow, the product of cross-sectional area and fluid speed is constant.

10. Define coefficient of linear, area, and volume thermal expansion and their relationship.

    α (linear), β (area), γ (volume) measure fractional expansion per degree. For isotropic solids: β = 2α and γ = 3α.

11. Distinguish between specific heat capacity and latent heat.

    Specific heat capacity is heat needed to raise unit mass by 1°C (Q = mcΔT). Latent heat is heat needed to change the phase of unit mass at constant temperature (Q = mL), with no temperature change.

12. Name the three modes of heat transfer and the medium each requires.

    Conduction (needs a medium, no bulk movement), convection (needs a fluid medium with bulk movement), radiation (needs no medium, travels as electromagnetic waves).

13. State the first law of thermodynamics.

    ΔQ = ΔU + ΔW: heat supplied to a system equals the increase in its internal energy plus the work done by the system.

14. Distinguish between isothermal and adiabatic processes.

    Isothermal: temperature constant (ΔU = 0, PV = constant), heat exchanged with surroundings. Adiabatic: no heat exchange (ΔQ = 0), PVᵞ = constant, temperature changes.

15. State the second law of thermodynamics (Kelvin–Planck statement) and define a heat engine's efficiency.

    No process can convert heat completely into work with no other effect. Efficiency η = W/Q₁ = 1 − Q₂/Q₁ (always less than 1).

16. State the postulates and key result of the kinetic theory of gases for pressure.

    Gas molecules are tiny, in random motion, with elastic collisions and negligible intermolecular forces. Pressure P = (1/3)ρ⟨v²⟩ = (1/3)(mN/V)⟨v²⟩.

17. State the law of equipartition of energy and the average KE of a gas molecule.

    Each degree of freedom carries average energy ½k_BT. The average translational KE per molecule = (3/2)k_BT (monatomic gas).

18. Define simple harmonic motion (SHM) and write its defining equation.

    SHM is oscillatory motion where restoring force is proportional to displacement and directed toward equilibrium: a = −ω²x, with displacement x = A sin(ωt + φ).

19. Write the time period of a simple pendulum and of a spring–mass system.

    Simple pendulum: T = 2π√(L/g). Spring–mass: T = 2π√(m/k).

20. In SHM, write the expressions for total energy and the maximum velocity.

    Total energy E = ½mω²A² (constant). Maximum velocity v_max = ωA, occurring at the mean position.

21. What is the relationship between wave speed, frequency, and wavelength?

    v = fλ (wave speed = frequency × wavelength).

22. Distinguish between transverse and longitudinal waves, with an example of each.

    In transverse waves particles vibrate perpendicular to wave direction (e.g., light, waves on a string). In longitudinal waves particles vibrate parallel to wave direction (e.g., sound in air).

23. What are beats, and what is the beat frequency?

    Beats are periodic variations in sound intensity from superposition of two waves of slightly different frequencies. Beat frequency = |f₁ − f₂|.

24. State the Doppler effect for sound and give the formula for observed frequency.

    The apparent change in frequency due to relative motion of source and observer. f' = f (v ± v_o)/(v ∓ v_s), where v is sound speed, v_o observer speed, v_s source speed (signs chosen by direction of approach).

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