As shown below, a square loop of wire of side a moves through a uniform magnetic field of magnitude B perpendicular to the page at constant velocity  directed to the right. Judd says that the emf induced in the loop is zero. Roger claims that it has magnitude B

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. Which one, if either, is correct, and why?
?
?

?

A.

Judd, because the magnetic flux through the loop is constant.

B.

Roger, because the magnetic flux through the loop is constant.

C.

Judd, because the magnetic flux through the loop is not constant if .

D.

Roger, because the magnetic flux through the loop is not constant if .

E.

Roger, because the magnetic flux through the loop is ?_B = 0.

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Answer: A

Physics & Space Science

The precision and number of significant figures in 1.003 km is

A. precision = .0001 km, significant figure = 4. B. precision = .001 km, significant figure = 4. C. precision = .0001 km, significant figure = 3. D. precision = .001 km, significant figure = 3. E. precision = .0001 km, significant figure = 2.

When a rocket forces exhaust gases downward, the exhaust gases

A) as the name implies, soon exhaust their influence. B) play no further role in the motion of the rocket. C) exert an upward force on the rocket.

After their rocket engines shut off, astronauts experience weightlessness in the orbiting Space Shuttle,

A. and they are accelerating because they are actually in free-fall. B. and they are accelerating because they have constant velocity as they pass overhead. C. but they cannot accelerate because their rocket engines are shut off. D. but they are not accelerating, since nothing actually has weight in space.

Microscopes are inherently limited by the wavelength of the light used. How much smaller (in order of magnitude) can we "see" using an electron microscope whose electrons have been accelerated through a potential difference of 50000 V than using red light (500 nm)?

a. 3 b. 4 c. 5 d. 6 e. 14