Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?
A) The star is getting hotter. B) The star is getting colder.
C) The star is moving toward us. D) The star is moving away from us.
C
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A solid conducting sphere of 10-cm radius has a net charge of 18 nC. If the potential at infinity is taken as zero, what is the potential at the center of the sphere?
a. 2.1 ?V b. 16 ?V c. 1.6 × 10^3 V d. >1.6 × 10^4 V e. 13 ?V
A long hollow cylindrical conductor (inner radius = 2.0 mm, outer radius = 4.0 mm) carries a current of 24 A distributed uniformly across its cross section. A long wire which is coaxial with the cylinder carries an equal current in the opposite direction. What is the magnitude of the magnetic field 3.0 mm from the axis?
a. 0.82 mT b. 0.93 mT c. 0.70 mT d. 0.58 mT e. 0.40 mT
Compared to the moons of Jupiter, the moons of the more distant Jovian planets
A) contain a higher proportion of rock B) are made of a mixture of rock and methane ice C) contain higher overall proportions of water ice as well as methane and other ices D) are made completely of methane ice
Which of the following choices best corresponds to what is required by the second law of thermodynamics for any process taking place in an isolated system?
a. entropy decreases b. entropy remains constant c. entropy increases d. entropy equals work done on the system