When current reverses direction in a wire, the surrounding magnetic field
A) also reverses direction.
B) becomes momentarily stronger.
C) contracts.
D) expands.
Answer: A
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In a circuit, a current of 1.10 A is drawn from a battery. The current then divides and passes through two resistors in parallel. One of the resistors has a value of 66 ? and the current through it is 0.480 A. What is the value of the other resistor?
a. 28.8 ? b. 51.1 ? c. 151 ? d. 20.1 ?
Ancient geologic processes as revealed in Paleozoic rock layers were
A) predominantly volcanic in origin. B) primarily glacial. C) predominantly processes of erosion and sedimentation. D) very similar to processes seen today.
Which of the following is not a piece of evidence supporting the conclusion that active galactic nuclei are powered by accretion disks around massive black holes?
A) The total amount of radiation coming from the galactic center can, in some cases, exceed 100 times the total luminosity of the Milky Way Galaxy. B) Infrared observations show that many stars are forming near the centers of active galaxies. C) Observed radiation from the galactic center can vary significantly in brightness in times as short as a few days. D) Spectral lines from the galactic center indicate that clouds of gas are orbiting a central object at very high speed. E) Radio observations sometimes show long jets of material that can extend millions of light-years out from the galactic center.
The diagram below shows three approximate locations of the sun along the western horizon. Which number indicates the location of the sun at sunset on the vernal equinox for an observer at a latitude of 48° S?
a. 1
b. 2
c. 3
d. The sun will set in the east for an observer in the southern hemisphere.
e. The sun will not set on vernal equinox at this latitude.