From hottest to coolest, the order of the spectral types of stars is

A) OBAFGKM.
B) OBAGFKM.
C) ABFGKMO.
D) OMKGFBA.
E) ABCDEFG.

A

Physics & Space Science

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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.

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Physics & Space Science

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

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Physics & Space Science

Use the band theory of semiconductors to choose the most correct statement below

a. A semiconductor primarily differs from an insulator in size of band gap. b.Materials that are generally called conductors contain an overlap in the conduction and valence bands. c. Conductors and semimetals are similar in band structure because of large band gaps. d. Electrons in insulators at room temperature can easily cross the band gaps. e. Semimetal materials are arranged structurally like metals but act as insulators because they have large band gaps.

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Physics & Space Science

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

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Physics & Space Science