The source of electromagnetic waves is vibrating
A) electric charges.
B) atoms.
C) molecules.
D) energy fields.
Answer: A
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A hollow conducting spherical shell of radius 1.20 cm carries a charge of -5.20 nC. What is the electric field at a distance of 1.50 cm from the center of the shell?
A. 
B. 0 N/C
C. 
D. 
E. 
Intensity: The intensity of the waves from a point source at a distance d from the source is I. What is the intensity at a distance 2d from the source?
A. 4I
B. 2I
C. I/2
D. I/4
E. I/
Consider a compass with a square magnet placed in a uniform electric field, as shown below. If the magnet is free to pivot around an axis pointing toward the viewer that goes through the point at the magnet’s center, which way will it turn (if it does) in this field?
A. Clockwise, to align itself with the field.
B. Counter clockwise, to align itself with the field.
C. 180° either clockwise or counter clockwise.
D. It won’t turn, as it is already aligned with the field.
E. It won’t turn, because the field wants to twist it around a different axis altogether.
F. It won’t turn because it is not affected by this field.
Increasing the spring constant k of a mass-and-spring system causes what kind of change in the resonant frequency of the system? (Assume no change in the system's mass m.)
A) The frequency increases. B) The frequency decreases. C) There is no change in the frequency. D) The frequency increases if the ratio k/m is greater than or equal to 1 and decreases if the ratio k/m is less than 1. E) The frequency increases if the ratio k/m is less than or equal to 1 and decreases if the ratio k/m is greater than 1.