Which of the following happened first (after the Big Bang)?
A) Molecules formed.
B) Neutral atoms formed.
C) Protons formed.
D) Helium formed.
C) Protons formed.
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Which form of electromagnetic radiation is absorbed by carbon dioxide and water vapor in our atmosphere?
A) visible light B) ultraviolet C) infrared D) radio E) gamma rays
Suppose you are listening to a radio station that broadcasts at a frequency of 97 Mhz (megahertz). Which of the following statements is true?
A) The radio waves from the radio station are causing electrons in your radio's antenna to move up and down 97 million times each second. B) The radio waves from the radio station have a wavelength of 97 million meters. C) The "radio waves" received by your radio are not light waves like those we talk about in astronomy, but rather are a special type of sound wave. D) The radio station broadcasts its signal with a power of 97 million watts.
One long wire carries a current of 30 A along the entire x axis. A second long wire carries a current of 40 A perpendicular to the xy plane and passes through the point (0, 4, 0) m. What is the magnitude of the resulting magnetic field at the point y = 2.0 m on the y axis?
a. 4.0 ?T b. 5.0 ?T c. 3.0 ?T d. 7.0 ?T e. 1.0 ?T
Wire is wound on a square frame, 30 cm by 30 cm, to form a coil of 7 turns. The frame is mounted on a horizontal shaft through its center (perpendicular to the plane of the diagram), as shown in the figure
The coil is in clockwise rotation, with a period of 0.060 s. A uniform, horizontal, magnetic field of magnitude 0.40 T is present. At a given instant, the plane of the coil forms a 60° angle with the horizontal, as shown. At that instant, what is the magnitude of the emf induced in the coil? A) 13 V B) 23 V C) 2.1 V D) 3.6 V E) 26 V