Three long parallel wires each carry 2.0-A currents in the same direction. The wires are oriented vertically, and they pass through three of the corners of a horizontal square of side 4.0 cm
What is the magnitude of the magnetic field at the fourth (unoccupied) corner of the square due to these wires? (?0 = 4? × 10-7 T ? m/A)
A) 1.2 µT
B) 2.1 µT
C) 12 µT
D) 21 µT
E) 0 T
D
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Earth and the moon could not have condensed from the same materials because they have different densities and compositions
Indicate whether the statement is true or false
Which of the following is a problem inherent in all large radio telescopes?
A) They are badly affected by poor seeing and atmospheric turbulence. B) The lightest breeze shakes them, making the observations blurry. C) Their waves are blocked by water vapor, so they must be located in deserts. D) Radio waves have long wavelengths, so radio telescopes have poor resolution. E) The dust clouds in the Milky Way block almost all wavelengths except light.
Consider a flat steel plate with a hole through its center. When the plate's temperature is decreased, the hole will
A) contract only if it takes up more than half the plate's surface area. B) expand if it takes up less than half the plate's surface area. C) contract. D) expand.
Lisa Ann is nearsighted with a near point of 75. cm
(a) What FOCAL LENGTH is this? (b) What POWER lens is needed to correct her nearsightedness (assuming distance from lens to eye is negligible)?