An iron core in a transformer
A) guides magnetic field lines.
B) shields unwanted external electric or magnetic fields.
C) separates the primary and secondary regions.
D) reduces energy losses.
Answer: A
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Fossils are found
A) mostly in igneous rocks B) in all kinds of rocks with equal probability C) mostly in sedimentary rocks D) only in metamorphic rocks
Which method of fueling your car is likely to be more energy efficient, and why: gasoline used in a standard car engine or electricity taken from a coal-fueled generating plant and stored in lightweight car batteries? Assume that the batteries
convert electricity to work at 100% efficiency, and that electricity is transported from the power plant to the car at 100% efficiency. A) Gasoline used in a standard car engine, because a car engine's fuel burns hotter and more efficiently than does the coal in a coal-fired power plant. B) Electricity from a coal-fired generating plant, because a car engine is a heat engine, and must follow the second law of thermodynamics, whereas a coal-fired generating plant is not. C) Gasoline used in a standard car engine, because a car engine burns its fuel directly in the automobile rather than miles away at the power plant. D) Electricity from a coal-fired generating plant, because such a plant runs at higher energy-efficiency than does a car engine. E) It wouldn't make any difference, because both the car engine and the generating plant are heat engines and are thus subject to the second law of thermodynamics.
Two plane mirrors make an angle of 50° with one another. A ray of light parallel to mirror #1 reflects off mirror #2 and then strikes mirror #1 . What is the angle of incidence the ray makes with mirror #1?
a. 50° c. 40° b. The answer is not given. d. 55°
Reverse bias permits full current through a pn junction.
a. True b. False