For an ideal inductor in an ac circuit, how much energy is stored in the inductor at the instant when the current is zero?
A. maximum
B. 1?2 maximum
C. 0.707 maximum
D. zero
D. zero
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Radiation Pressure: Two light beams of different frequency but the same intensity fall on a black (totally absorbing) surface, striking perpendicular to the surface. Which of the following statements are true? (There could be more than one correct choice.)
A. The high-frequency beam exerts more pressure on the surface. B. Both beams exert the same pressure on the surface. C. If the surface were painted white (totally reflecting), the pressure on it would be less than when it was black. D. Painting the surface white would not affect the pressure on it due to these beams. E. The light beams exert no pressure on the surface because light is just energy.
Which of the following statements about stellar parallax is true?
A) The closer a star is to us, the more parallax it exhibits. B) It takes at least 10 years of observation to measure a star's parallax. C) The amount of parallax we see depends on how fast a star is moving relative to us. D) Stellar parallax was first observed by ancient Greek astronomers. E) We observe all stars to exhibit at least a slight amount of parallax.
A compound microscope has a 18-cm-long barrel and an objective lens with a focal length of 8.0 mm
What is the focal length of the eyepiece to give a total magnification of 240? It is adjusted for minimum eyestrain for persons with a near point of 25 cm. A) 1.3 m B) 1.5 cm C) 1.9 cm D) 2.1 cm E) 2.3 cm
The point P lies along the perpendicular bisector of the line connecting two long straight wires S and T perpendicular to the page. A set of directions A through H is shown next to the diagram. When the two equal currents in the wires are directed up out of the page, the direction of the magnetic field at P is closest to the direction of
a.
E.
b.
F.
c.
G.
d.
H.
e.
A.