An 800-kHz radio signal is detected at a point 4.5 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 0.63 V/m
Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. What is the magnetic field amplitude of the signal at that point? (c = 3.0 × 108 m/s,
?0 = 4? × 10-7 T ? m/A, ?0 = 8.85 × 10-12 C2/N ? m2)
A) 2.1 nT
B) 1.7 nT
C) 1.3 nT
D) 2.5 nT
E) 2.9 nT
Answer: A
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Parallel Wires: Two long parallel wires are placed side-by-side on a horizontal table and carry current in the same direction. The current in one wire is 20 A, and the current in the other wire is 5 A. If the magnetic force on the 20-A wire has magnitude F, what is the magnitude of the magnetic force on the 5-A wire? No external magnetic fields are present.
A. 4F B. 2F C. F D. F/2 E. F/4
One parsec is equal to 3.26 light-years.
Answer the following statement true (T) or false (F)
The ______________ effect provides evidence of motions within other planetary systems
Fill in the blank(s) with correct word
An eyeglass lens is cut with one surface having a radius R1 and the other surface having a radius R2, with R1 < R2 . Both positive radii are measured from the same side with R2 being the side closer to the eye. Is this convex-concave lens a converging lens or a diverging lens?
a. This is neither, since a lens cannot be made this way. b. This is a diverging lens. c. This can be either a converging or diverging lens, as more information is needed for a final determination. d. This is a converging lens.