CUET UG 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. What is the principle and use of a cyclotron?

   A cyclotron accelerates charged particles using a high-frequency alternating voltage and a perpendicular magnetic field that makes them move in spiral paths. Cyclotron frequency f = qB/(2πm). It is used to accelerate ions/particles to high energies.

2. Define the magnetic dipole moment of a current loop.

   m = NIA, where N is number of turns, I the current, A the loop area. It is directed perpendicular to the loop plane (right-hand rule). SI unit: A·m².

3. State the elements of Earth's magnetism.

   The three elements are: (1) magnetic declination (angle between geographic and magnetic meridians), (2) magnetic dip/inclination (angle of total field with horizontal), and (3) horizontal component of Earth's field (B_H).

4. Compare diamagnetic, paramagnetic, and ferromagnetic materials.

   Diamagnetic: weakly repelled, χ small negative (e.g., Bi, Cu). Paramagnetic: weakly attracted, χ small positive (e.g., Al, Na). Ferromagnetic: strongly attracted, χ large positive, retain magnetism (e.g., Fe, Co, Ni).

5. State Curie's law for paramagnetic materials.

   Magnetic susceptibility is inversely proportional to absolute temperature: χ = C/T, where C is the Curie constant. Above the Curie temperature, ferromagnets become paramagnetic.

6. State Faraday's laws of electromagnetic induction.

   First law: an EMF is induced whenever magnetic flux through a circuit changes. Second law: the induced EMF equals the negative rate of change of flux, ε = −dΦ/dt (N turns: ε = −N dΦ/dt).

7. State Lenz's law and what conservation principle it embodies.

   The induced current always opposes the change in magnetic flux that produces it. It is a consequence of the law of conservation of energy.

8. Define self-inductance and give the EMF it produces.

   Self-inductance L relates flux to current: Φ = LI. The self-induced EMF is ε = −L(dI/dt). SI unit: henry (H).

9. Define mutual inductance.

   Mutual inductance M is the flux linkage in one coil per unit current in another: Φ₂ = MI₁, with induced EMF ε₂ = −M(dI₁/dt). SI unit: henry (H).

10. What is the EMF induced in a rod of length L moving with velocity v perpendicular to field B (motional EMF)?

    ε = BLv.

11. Define RMS value of alternating current and relate it to peak value.

    The RMS (root-mean-square) value is the equivalent DC that produces the same heating effect. For sinusoidal AC: I_rms = I₀/√2 ≈ 0.707 I₀.

12. Define inductive reactance and capacitive reactance.

    Inductive reactance X_L = ωL = 2πfL (increases with frequency). Capacitive reactance X_C = 1/(ωC) = 1/(2πfC) (decreases with frequency).

13. Write the impedance of a series LCR circuit.

    Z = √[R² + (X_L − X_C)²], where X_L = ωL and X_C = 1/(ωC).

14. State the condition for resonance in a series LCR circuit and the resonant frequency.

    Resonance occurs when X_L = X_C, so impedance is minimum (= R) and current is maximum. Resonant frequency f₀ = 1/(2π√(LC)).

15. Define power factor in an AC circuit and write average power.

    Power factor = cosφ = R/Z, where φ is the phase angle between voltage and current. Average power P = V_rms·I_rms·cosφ.

16. State the working principle of a transformer and the turns ratio relation.

    A transformer works on mutual induction, transferring AC power between coils. V_s/V_p = N_s/N_p = I_p/I_s (ideal transformer). Step-up increases voltage; step-down decreases it.

17. State the laws of reflection of light.

    (1) The incident ray, reflected ray, and normal lie in the same plane. (2) The angle of incidence equals the angle of reflection.

18. Write the mirror formula and the magnification for a spherical mirror.

    Mirror formula: 1/v + 1/u = 1/f. Magnification m = −v/u = h'/h.

19. State Snell's law of refraction.

    n₁ sinθ₁ = n₂ sinθ₂, i.e., the ratio sin(incidence)/sin(refraction) equals the relative refractive index. Refractive index n = c/v (speed of light in vacuum / in medium).

20. Define critical angle and the condition for total internal reflection.

    Critical angle θ_c is the angle of incidence (in the denser medium) for which the refraction angle is 90°: sinθ_c = 1/n. Total internal reflection occurs when light travels from denser to rarer medium and the angle of incidence exceeds θ_c.

21. Write the lens maker's formula.

    1/f = (n − 1)(1/R₁ − 1/R₂), where n is the lens refractive index and R₁, R₂ are the radii of curvature of its surfaces.

22. Define power of a lens and its SI unit.

    Power P = 1/f (with f in metres). It measures converging/diverging ability. SI unit: dioptre (D); convex lens has positive power, concave negative.

23. State Young's double-slit experiment condition for bright and dark fringes, and fringe width.

    Bright fringes (constructive): path difference = nλ. Dark fringes (destructive): path difference = (n+½)λ. Fringe width β = λD/d, where D is slit-to-screen distance and d the slit separation.

24. What is the energy of a photon and the threshold frequency in the photoelectric effect?

    Photon energy E = hν = hc/λ. Einstein's photoelectric equation: KE_max = hν − φ₀, where φ₀ = hν₀ is the work function and ν₀ the threshold frequency below which no emission occurs. Bohr radius and energy: E_n = −13.6/n² eV for hydrogen; in a P-N junction diode, the depletion region forms at the junction and the diode conducts in forward bias only.

What this deck covers

Physics flashcards FAQ