A transformer is to be designed to increase the 30 kV-rms output of a generator to the transmission-line voltage of 345 kV-rms. If the primary winding has 80 turns, how many turns must the secondary have?
a. 6
b. 70
c. 920
d. 9200
e. 12
c
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In principle, if we could see all the way to the cosmological horizon we could see the Big Bang taking place. However, our view is blocked for times before about 380,000 years after the Big Bang. Why?
A) Before that time, the universe was too crowded with stars. B) Before that time, the gas in the universe was dense and ionized and therefore did not allow light to travel freely. C) Before that time, the universe was dark so there was no light to illuminate anything. D) 380,000 years after the Big Bang marks the time when stars were first born, producing the light by which we can see the universe.
A recent sunspot maximum occurred in 2013 . What is the year of the sunspot maximum that immediately follows the 2013 maximum if the solar cycle continues?
a. 2017 b. 2019 c. 2022 d. 2024 e. The last cycle started a Maunder minimum and the next maximum cannot be predicted.
Sunspots occur in ______________ with the leading spot and the trailing spot having ________________ magnetic polarity
a. singles, same b. pairs, opposite c. singles, opposite d. pairs, same e. none of the others
Suppose that a ship is accelerating through space in such a way that the passengers are experiencing a constant force (resulting from the thrust of the ship) equivalent to the total weight of the ship and passengers on Earth. From the point of view of observers on Earth, how does the ship accelerate?
A) At first, it has a nearly constant acceleration of 9.8 m/s2. But as it approaches the speed of light, its acceleration gradually slows in such a way that it never stops accelerating, but it never reaches the speed of light either. B) It has a constant acceleration of 9.8 m/s2, therefore increasing its speed by 9.8 m/s with each passing second. C) At first, it has a large acceleration, much larger than 9.8 m/s2. But when it reaches the speed of light it stops accelerating. D) It has a constant acceleration of 9.8 m/s2 until it reaches a speed of half the speed of light. Then its acceleration suddenly slows so that it can't go much faster.