A white dwarf supernova event is very important to calibrating Hubble's Law. Why? Choose the best answer for the question
A) It is a very luminous standard candle.
B) It is a very rare event.
C) It can only happen to white dwarfs.
D) The white dwarf supernova in a galaxy tells us how fast a galaxy is expanding away from us.
A
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A 2-kg ball is held 4 m above the ground. Relative to the ground its potential energy is
A) 6 J. B) 8 J. C) 32 J. D) 80 J. E) more than 80 J.
How is the existence of Earth's unique atmosphere explained?
A) The oxygen in Earth's atmosphere is a result of early life on Earth. B) Volcanic gases containing nitrogen were outgassed from Earth's interior. C) As Earth cooled, water vapor fell out of the atmosphere to form the oceans. D) Ultraviolet radiation from the Sun freed the hydrogen, allowing it to escape. E) When Earth formed, its atmosphere formed from the gases most common in the early solar system.
A transformer is used to step up the voltage to a power line. If the stepped-up voltage is 10 times the original value, by how much will the power loss in the line decrease?
a. more than 95% b. between 10% and 20% c. between 20% and 95% d. There will be no change since the power into a transformer equals the power out.
Which of the following statements is incorrect?
a.
Capacitance is always positive.
b.
The symbol for potential difference between the plates of a capacitor is 
.
c.
Water is a polar molecule.
d.
When a dielectric is placed in a capacitor it serves to reduce the electric field.
e.
Nonpolar molecules cannot be used for dielectric material in a capacitor.