Based on the number of galaxies visible in the Hubble eXtreme Deep Field (Figure 20.1 in your text), the estimated number of galaxies in our observable universe is at least
A) 100 billion.
B) 100 million.
C) 50,000.
D) infinity.
A) 100 billion.
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Parallel Wires: Two parallel straight wires are 7.0 cm apart and 50 m long. Each one carries a 18-A current in the same direction. One wire is securely anchored, and the other is attached in the center to a movable cart. If the force needed to move the wire when it is not attached to the cart is negligible, with what magnitude force does the wire pull on the cart? (?0 = 4? × 10-7 T ? m/A)
A. 46 mN B. 37 mN C. 66 mN D. 93 mN
Faraday's Law: As shown in the figure, a large round loop of 269 turns and radius 67.0 cm carries a current of I = 78.0 A. A small square loop of 31.0 turns and 1.00 cm on a side is placed at the center of the large loop. If the current in the large loop drops to 0.00 A in 0.0470 s, find the induced emf in the small loop. The square loop is small enough that you can assume that the magnetic field in its region is uniform and equal to the magnetic field at the center of the round loop. (?0 = 4? × 10-7 T ? m/A)
Fill in the blank(s) with the appropriate word(s).
How much heat is produced in the 10-? resistor in 5.0 s when ? = 18 V?
a.
72 J
b.
32 J
c.
50 J
d.
18 J
e.
90 J
A standing wave is likely produced when
A) two waves overlap. B) a wave reflects upon itself. C) the speed of the wave is zero or near zero. D) the amplitude of a wave exceeds its wavelength.