How much power does a sphere with a radius of 10 cm radiate if is has an emissivity e = 1.0 and is kept at a temperature of 400 K? The Stefan-Boltzmann constant is 5.67 x 10-8 W/(m2•K4)
A) 60 W
B) 70 W
C) 180 W
D) 210 W
E) 360 W
C
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Compared to a smaller-objective lens, a larger-objective lens makes a star's image
a. brighter. b. dimmer. c. no effect.
At point P the magnetic field due to a long straight wire carrying a current of 2.0 A is 1.2 µT. How far is P from the wire? (?0 = 4? × 10-7 T ? m/
A) A) 11 cm B) 22 cm C) 33 cm D) 44 cm E) 55 cm
Motional Emf: A conducting rod whose length is ? = 1.60 m is placed on frictionless U-shaped metal rails that is connected to a lightbulb having a resistance of 4.00 ? as shown in the figure. The rails and the rod are in the plane of the page. A constant uniform magnetic field of strength 2.20 T is applied perpendicular to and out of the paper. What is the magnitude of the external applied force needed to move the rod to the right with a constant speed of 6.00 m/s?
A. 8.60 N B. 9.30 N C. 10.6 N D. 12.6 N E. 18.6 N
________ are star-like objects that contain less than 0.08 solar masses and will never raise their core temperatures high enough that the proton-proton chain can begin. Other minor fusion reactions do occur in these objects. They fall in a gap between the low-mass M dwarf stars and the massive planets in which nuclear fusion never occurs
a. Brown dwarfs b. Herbig-Haro objects c. Bok globules d. T-Tauri star e. Main-sequence stars