If the Sun and stars are supported by gas pressure, what supports a white dwarf?
What will be an ideal response?
A normal star is supported by energy flowing outward from its core, but a white dwarf can't generate energy by nuclear fusion. It has exhausted its hydrogen and helium fuels and converted them into carbon and oxygen. When a star collapses into a white dwarf, it converts gravitational energy into thermal energy. Its interior becomes very hot, but it can't get hot enough to fuse its carbon-oxygen interior. Instead the star contracts until it becomes degenerate. The white dwarf is supported against its own gravity by the pressure of its degenerate electrons.
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When the accelerating voltage in an X-ray tube is doubled, the minimum wavelength of the X-rays
A) is increased to twice the original value. B) is increased to four times the original value. C) is decreased to one-fourth the original value. D) is decreased to one-half the original value.
An inductor, battery, resistance, and ammeter and switch are connected in series. If the switch, initially open, is now closed, what is the current's final value?
a. zero b. battery voltage divided by inductance c. battery voltage times inductance d. battery voltage divided by resistance
What size capacitor must be placed in series with a 40-mH coil so the circuit will oscillate with a frequency of 1000 Hz?
A) 0.63 ?F B) 0.50 ?F C) 0.22 ?F D) 0.17 ?F
Magnets may be found only
a. in natural domains in the environment where there is magnetite. b. in pieces of all metals. c. in domains. d. where there are electric outlets. e. where there are aligned domains in a material.