The magnitude of the Poynting vector of a planar electromagnetic wave has an average value of 0.724 W/m2
What is the maximum value of the magnetic field in the wave? (c = 3.0 x 108 m/s, ?0 = 4? × 10-7 T ? m/A, ?0 = 8.85 × 10-12 C2/N ? m2)
A) 77.9 nT
B) 55.1 nT
C) 38.9 nT
D) 108 nT
E) 156 nT
A
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A stepped steel shaft (G 5 75 GPa) with diameters d1 5 36 mm and d2 5 32 mm is twisted by torques T at each end. Segment lengths are L1 5 0.9 m and L2 5 0.75 m. If the allowable shear stress is 28 MPa and maximum allowable twist is 1.88, the maximum permissible torque is approximately:
(A) 142 N?m
(B) 180 N?m
(C) 185 N?m
(D) 257 N?m
That Polaris will not always be the pole star is due to
A) the sidereal day being shorter than the solar day. B) precession shifting the celestial pole. C) the Moon following the ecliptic, instead of the equator. D) the Earth's revolution being slightly less than exactly 365.25 days. E) the Solar winds blowing the Earth farther away from the Sun.
A ZAMS star is located _______________________
a. above the main sequence b. on the upper edge of the main sequence c. in the middle of the main sequence d. on the lower edge of the main sequence
For periodic motion, the maximum displacement from the equilibrium point is called the
A) amplitude. B) wavelength. C) frequency. D) period. E) energy.