Two solenoids are each made of 2000 turns of copper wire per meter. Solenoid I is 2 m long, while solenoid II is 1 m long. When equal currents are present in the two solenoids, the ratio of the magnetic field BI along the axis of solenoid I to the magnetic field BII along the axis of solenoid II, BI/BII, is
a. 1/4.
b. 1/2.
c. 1.
d. 2
e. 4.
[Ques. 2] A toroid is made of 2000 turns of wire of radius 2.00 cm formed into a donut-shape of inner radius 10.0 cm and outer radius 14.0 cm. When a 30.0-A current is present in the toroid, the magnetic field at a distance of 11.0 cm from the center of the toroid is
a. 0.0857 T.
b. 0.109 T.
c. 0.120 T.
d. 0.600 T.
e. 0.685 T.
[Ques. 3] When a microwave filter consisting of vertical parallel metal rods is in the absorbing position, oscillating currents are set up in the rods. At any one instant, the current in each rod has the same magnitude and direction. At that instant
a. the rods will try to move apart horizontally.
b. the rods will try to move together horizontally.
c. the rods will try to shift vertically upwards.
d. the rods will try to shift vertically downwards.
e. the rods will not be affected because the source of current is not a battery.
[Ques. 4] At a point in space where the magnetic field is measured, the magnetic field produced by a current element
a. points radially away in the direction from the current element to the point in space.
b. points radially in the direction from the point in space towards the current element.
c. points in a direction parallel to the current element.
d. points in a direction parallel to but opposite in direction to the current element.
e. points in a direction that is perpendicular to the current element and perpendicular to the radial direction.
[Ques. 5] By using a compass to measure the magnetic field direction at various points adjacent to a long straight wire, you can show that the wire's magnetic field lines are
a. straight lines in space that go from one magnetic charge to another.
b. straight lines in space that are parallel to the wire.
c. straight lines in space that are perpendicular to the wire.
d. circles that have their centers on the wire and lie in planes perpendicular to the wire.
e. circles that have the wire lying along a diameter of the circle.
[Ques. 6] When the number of turns in a solenoid and its length are both doubled, the ratio of the magnitude of the new magnetic field inside to the magnitude of the original magnetic field inside is what?
a. 0.25
b. 0.50
c. 1
d. 2
e. 4
[Ques. 7] A current element (length = 1.0 cm) lies along the x axis with its center at x = 0 and carries a 20-A current in the positive x direction. Consider only the field of this current element and decide which combination of the following statements is correct. 1 . The field at (0, 0, 1.0 m) is in the positive z direction. 2 . The field at (0, 1.0 m, 0) is in the negative y direction. 3 . The field at (1.0 m, 0, 0) is zero. 4 . The field at (0, 0, 1.0 m) is in the negative y direction.
a. 3 and 4
b. 1 and 3
c. 2 and 4
d. 1 and 2
e. None of these
[Ques. 8] A long solenoid (1000 turns/m) carries a current of 25 mA and has an inside radius of 2.0 cm. A long wire which is parallel to and 4.0 cm from the axis of the solenoid carries a current of 6.0 A. What is the magnitude of the magnetic field at a point on the axis of the solenoid?
a. 51 T
b. 61 T
c. 43 T
d. 81 T
e. 1.4 T
[Ques. 9] A long solenoid (1500 turns/m) carries a current of 20 mA and has an inside diameter of 4.0 cm. A long wire carries a current of 2.0 A along the axis of the solenoid. What is the magnitude of the magnetic field at a point that is inside the solenoid and 1.0 cm from the wire?
a. 78 T
b. 55 T
c. 48 T
d. 68 T
e. 2.0 T
[Ques. 10] A long solenoid (n = 1200 turns/m, radius = 2.0 cm) has a current of a 0.30 A in its winding. A long wire carrying a current of 20 A is parallel to and 1.0 cm from the axis of the solenoid. What is the magnitude of the resulting magnetic field at a point on the axis of the solenoid?
a. 0.60 mT
b. 0.85 mT
c. 52 T
d. 0.40 mT
e. 0.75 mT
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