A step-up transformer that doubles the input voltage is designed to work with an input voltage that varies at 60 Hz. The frequency with which the output voltage varies is ________ Hz.
Fill in the blank(s) with the appropriate word(s).
60
sixty
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Why does the Big Bang theory predict that the cosmic microwave background should have an essentially perfect thermal radiation spectrum?
A) This radiation came from the heat of the universe itself. B) The spectrum of pure hydrogen is a perfect thermal radiation spectrum. C) The spectrum of 75 percent hydrogen and 25 percent helium is a perfect thermal radiation spectrum. D) The light from all the stars and gas in the sky averaged over the entire universe is a perfect thermal radiation spectrum. E) The first stars that formed in the universe must all have had the same temperature.
Evidence that the cosmic background radiation really is the remnant of a Big Bang comes from predicting characteristics of remnant radiation from the Big Bang and comparing these predictions with observations
Four of the five statements below are real. Which one is fictitious? A) The cosmic background radiation is expected to have a temperature just a few degrees above absolute zero, and its actual temperature turns out to be about 3 K (actually 2.7 K). B) The cosmic background radiation is expected to have a perfect thermal spectrum, and observations from the COBE spacecraft verify this prediction. C) The cosmic background radiation is expected to contain spectral lines of hydrogen and helium, and it does. D) The cosmic background radiation is expected to look essentially the same in all directions, and it does. E) The cosmic background radiation is expected to have tiny temperature fluctuations at the level of about 1 part in 100,000. Such fluctuations were found in the COBE data.
Two blocks are accelerated across a horizontal frictionless surface as shown. Frictional forces keep the two blocks from sliding relative to each other, and the two move with the same acceleration. If F = 1.2 N and M = 1.0 kg, what is the horizontal component (frictional force) of the force of the small block on the large block?
a.
0.48 N to the right
b.
0.72 N to the right
c.
0.72 N to the left
d.
0.48 N to the left
e.
0.65 N to the left
Infrared waves have a ________ wavelength than microwaves.
Fill in the blank(s) with the appropriate word(s).