How did Edwin Hubble measure the distance to the Andromeda Galaxy?
A) He measured its parallax.
B) He used Cepheid variables in the Andromeda Galaxy.
C) He deduced it from its redshift.
D) He used white dwarf supernovae in the Andromeda Galaxy.
B) He used Cepheid variables in the Andromeda Galaxy.
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Terminal Voltage and Internal Resistance: A heating element having a resistance (at its operating temperature) of 148 ? is connected to a battery having an emf of 523 V and unknown internal resistance.It is found that heat energy is being generated in the resistance of the heating element at a rate of 66.0 W. What is the rate at which heat energy is being generated in the internal resistance of the battery?
Fill in the blank(s) with the appropriate word(s).
At a temperature of 1090°C (2000°F), the superalloys with the highest strength in a 1000-hour stress rupture test are
(a) Small-grained polycrystals. (b) Strain-hardened polycrystals. (c) Single crystals. (d) Directionally solidified polycrystals.
The ________ is the spherical outgassing as a comet nucleus is heated by the Sun. The process by which small debris condenses into planetesimals is ________.
Fill in the blank(s) with the appropriate word(s).
A quantity that measures the opposition to the flow of charge is __________
Fill in the blank(s) with correct word