17. A negatively charged particle of mass m and charge q＜ 0 is restricted to move freely along the axis of a circular ring of radius R. A positive charge is uniformly distributed over the ring with a charge density (charge per unit length) λ＞ 0. Suppose the vertical coordinate of the particle relative to the center of the circular ring is y and y << R. Find the period of oscillation for small y:
(A)2πR
(B) 2πR
(C) 2πR
(D)πR

13. Which of the following statements about the Carnot engine is not correct? (A) The efficiency of a Carnot engine operating between temperatures T₁ and T2 (T₁ ＞ T2) is 1 – T2/T1. (B) The efficiency of any reversible engine is identical to that of a Carnot engine for given two heat reservoirs. (C) A Carnot engine has the best efficiency for given two heat reservoirs. (D) The entropy of a Carnot engine during a cycle remains constant.

14. Consider a partial circuit shown in the figure. Suppose every resistor is of identical resistance R. Find the effective resistance between A and B: (A) R (B) R/2 (C) 2R/3 (D) R/6.

15. A metal sphere of radius 2R stores an amount of charge Q initially.It then connects to another metal sphere of radius R by a conductingwire, which is removed after the charge is redistributed. Suppose the two spheres are far away apart.The ratio of the electric-field strength just outside the surface of the larger sphere to that of the smaller spheres is (A) 2:1 (B) 3:2 (C) 1:3 (D) 1:2.

16. A henry (H) is the same as (A) J/V (B) C/J (C) J/V2 (D) J/A2.

18. Suppose H+ and He2+ particles are injected into the device as shown in the figure from the left hole. Once they come out from the right hole, they immediately enter a region of another 9 uniform magnetic field B'perpendicular to their velocities. What is the ratio of radii of their circular motion rH+/rHe2+ under the field B'? (A) 2 (B) 1/2 (C) 1/(D) 4.

19. In an experiment on Newton's rings as shown in the figure, where we consider a lens of maximum thickness t and refractive index n. The radius of curvature of the spherical surface is R. When a light of wavelength A is incident from the top, the observed radius of the 3th bright fringe is given by (A) (B) (C) (D) 2Rλ/t.

20. A Rydberg atom is an atom with one of its electrons being excited to a state of a very large principle quantum number n, called a Rydberg state. For a Rydberg hydrogen atom whose diameter is approximately 1 µm, estimate the corresponding principle quantum number n: (Hint: For the ground state, n = 1, the diameter of a hydrogen atom is approximately 1 Å.)(A) 80 (B) 100 (C) 120 (D) 140.

21. Alice is initially on the moon and takes a rocket of speed 0.8 c to the earth. How long does it take for Alice to arrive at the earth according to Alice's watch supposing the moon-to-earth distance is approximately 4 × 10⁵ km? (A) 0.01 s (B) 0.1 s (C) 1 s (D) 10 s.

22. Consider an electron contained in a one-dimensional box of size L. What is the wavelength of the emitted photon corresponding to a transition from n = 3 to n = 2?(A)(B) (C)(D)

23. Consider two inertial frames, S and S', with S' moving along the +x axis of frame S at speed v. A particle, when viewed in frame S', travels at speed u' at angle θ' to the +x direction of frame S'. The angle θ of the particle's velocity (viewed by frame S) relative to the +x axis of frame S satisfies (A) tan θ = (B) tan θ' = (C) tan θ =(D) tan θ' =