Which of these did NOT occur at decoupling?
A) The cosmic microwave radiation was released from matter.
B) Neutral atoms were formed.
C) Matter dominated radiation.
D) Electrons began to orbit protons.
E) The universe became transparent.
C
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A 460-turn solenoid of length 30.0 cm and radius 4.00 cm carries a current of 3.50 A. What is the magnetic field strength inside the coil at its midpoint?What is the magnetic flux through a circular cross-sectional area of the solenoid at its midpoint?
a. 1.02E–5 T/m2 b. 3.05E–6 T/m2 c. 2.49E–7 T/m2 d. 3.39E–5 T/m2
A coil of 150 turns of wire is in the form of a circle, carries a current of 63 mA, and sits in the center of a dipole magnet that produces a uniform magnetic field of strength 1.5 T. The torque on the coil has a maximum value of 0.25 Nm. What is the radius of the coils?
A. 9.2 cm B. 13 cm C. 0.56 cm D. 7.5 cm
A 50.0-N box is sliding on a rough horizontal floor, and the only horizontal force acting on it is friction. You observe that at one instant the box is sliding to the right at 1.75 m/s and that it stops in 2.25 s with uniform acceleration
What magnitude force does friction exert on this box? A) 3.97 N B) 8.93 N C) 38.9 N D) 50.0 N E) 490 N
New telescopes are using "adaptive optics.". What is that?
a. using parabolic instead of spherical mirrors b. using computer image processing to enhance images c. building mirrors in hexagonal segments d. continually adjusting the mirror's shape during observations