Which of the following materials is most appropriate for a design requiring a material with a high magnetic susceptibility that will be subjected to an alternating magnetic field of 60 Hz?
(a) Fe-3 wt. % Si
(b) MnO
(c) Alnico-5
(d) Fe3O4
(a) Fe-3 wt. % Si
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An H-R diagram for a globular cluster will show a horizontal branch—a line of stars above the main-sequence but to the left of the subgiants and red giants. Which of the following statements about these horizontal branch stars is true?
A) They have inert (non-burning) carbon cores. B) Their sole source of energy is hydrogen shell burning. C) They generate energy through both hydrogen fusion and helium fusion. D) In a particular star cluster, all horizontal branch stars have the same spectral type.
The fact that we can only calculate probabilities for values of physical quantities in quantum measurements means that
a. radiation and matter are not described by mathematical relations between measurements. b. the probabilities cannot be calculated from mathematical relationships. c. the results of physical measurements bear no relationship to theory. d. the average values of a large number of measurements correspond to the calculated probabilities. e. the average of the values calculated in a large number of different theories corresponds to the results of a measurement.
A coil of 150 turns of wire is in the form of a circle, carries a current of 63 mA, and sits in the center of a dipole magnet that produces a uniform magnetic field of strength 1.5 T. The torque on the coil has a maximum value of 0.25 Nm. What is the radius of the coils?
A. 9.2 cm B. 13 cm C. 0.56 cm D. 7.5 cm
Which of the following is a technique that can be used to speed up a spacecraft without the need for extra fuel?
A) a gravitational slingshot, in which the spacecraft gains momentum by flying near a planet B) releasing unnecessary weight after takeoff to make the spacecraft lighter C) flattening after takeoff to make the spacecraft more aerodynamic D) landing on a fast-moving asteroid and relaunching at high speed E) collect material in space that can power the spacecraft