15. What is the magnitude of the spin angular momentum of a spin-1/2 particle? (A) s = (B) s = (C) s = (D) s = (E) s = ℏ

7. Which of the following statements about superconductivity is correct? (A) All materials become superconducting below 30 K (B) The resistance of a superconductor is zero (C) Superconductivity violates the first law of thermodynamics (D) Superconductivity violates the second law of thermodynamics (E) All the above are incorrect