A 60.0-Hz ac generator with a peak voltage of 110 V drives a series RL circuit with R = 10.0 ? and L = 10.0 mH. The power factor, cos ?, is
a. ?1.00.
b. ?0.936.
c. +0.943.
d. +0.936.
e. +1.00.
d
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Venus's surface temperature is fairly uniform from the equator to the poles because
a. Venus rotates very rapidly, which causes strong zonal winds. b. Venus is covered by a thick cloud layer that absorbs most of the sunlight that falls on it. c. the carbon dioxide in Venus's atmosphere efficiently emits infrared radiation. d. Venus rotates slowly so Coriolis forces do not disrupt Hadley circulation. e. Venus's orbit is nearly perfectly circular.
A resistor is connected to an ideal ac power supply. (a) The phase angle between the current and voltage is A. 0 B) ?/2 radians. C) -?/2 radians. D) ? radians. E) 3?/4 radians
(b) The current in the resistor A. leads the voltage across the resistor by 90°. B) lags the voltage across the resistor by 90°. C) is in phase with the voltage across the resistor. D) the voltage across the resistor by 45°. E) lags the voltage across the resistor by 45°. (c) How does the average power dissipated in the resistor change as the frequency in the ac power supply decreases? A. It decreases. B) It increases. C) It does not change. D) It increases or decreases depending on the sign of the phase angle.
The Rankine temperature scale has Fahrenheit degrees and a zero point at absolute zero. What is the Fahrenheit temperature of 62 Rankine?
a. –397.7 °F b. 111.6 °F c. 211.2 °F d. –238.7 °F
What is the moderator of a nuclear reactor?
a. The control rods that halt a chain reaction if it is out of control. b. A substance that absorbs neutrons to keep the reaction in control. c. The material that slows down the neutrons to induce more chain reactions. d. The material that speeds up the neutrons to induce more chain reactions. e. The name for the fissionable material itself (usually uranium).