Magnetic Field of a Long Wire: A long straight wire carrying a 4-A current is placed along the x-axis as shown in the figure. What is the magnitude of the magnetic field at a point P, located at y = 2 cm, due to the current in this wire? (?0 = 4? × 10-7 T ? m/A)

A. 20 ?T
B. 30 ?T
C. 40 ?T
D. 50 ?T
E. 60 ?T


Answer: C

Physics & Space Science

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Sebastian has drawn a free-body diagram for a ladder of mass m leaning against a frictionless wall. His diagram is shown below. What is his error? ? ?

A.

 is in the wrong direction.

B.
 should be directed upwards, not down.

C.
 should be perpendicular to the wall, not parallel to it.

D.
  should be down into the floor for    to have the given direction.

E.
 is correct, but there should also be a force perpendicular to the wall.

Physics & Space Science

How many valence electrons does boron (B, atomic no. = 5) have?

A) 1 B) 2 C) 3 D) 4 E) 5

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The pressure inside a commercial airliner is maintained at 1.00 atm (105 Pa). What is the net outward force exerted on a 1.0 m × 2.0 m cabin door if the outside pressure is 0.30 atm?

a. 140 N b. 1 400 N c. 14 000 N d. 140 000 N

Physics & Space Science

Rank the degenerate pressures from least supportive to most supportive:

a. electron, neutron, black hole b. black hole, neutron, electron c. neutron, electron d. electron, neutron

Physics & Space Science