From hottest to coolest, the order of the spectral types of stars is
A) OBAFGKM.
B) OBAGFKM.
C) ABFGKMO.
D) OMKGFBA.
E) ABCDEFG.
A
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Equal but opposite charges Q are placed on the square plates of an air-filled parallel-plate capacitor. The plates are then pulled apart to twice their original separation, which is small compared to the dimensions of the plates
Which of the following statements about this capacitor are true? (There may be more than one correct choice.) A) The capacitance has doubled. B) The electric field between the plates has increased. C) The energy stored in the capacitor has doubled. D) The energy density in the capacitor has increased. E) The potential difference across the plates has doubled.
In a diagram of electric field lines, q1 has 9 lines going into it and q2 has 27 lines going out of it. If one of the charges is -40 mC, which of the following could be the other one?
A. -120 mC B. 18.0 mC C. -18.0 mC D. 120 mC E. none of the these choices are correct
Use the band theory of semiconductors to choose the most correct statement below
Earth's rotation is connected with a very slow celestial motion that can be detected only over _____
a. centuries b. decades c. a year d. a few months e. short brief periods