Solenoid 1 has a length L, cross-sectional area A, and N turns. Solenoid 2 has a length 2L, cross-sectional area 2A, and 2N turns. Which long solenoid has the greater magnetic field at its center when equal currents are going through them?
a. Both have the same magnetic field. b. 1
c. 2
d. Since it depends on the values of A and L, none of the above are correct.
[Ques. 2] A centrifuge rotates at 100 rev/s (i.e., 628 rad/s). If the test tube places the suspension at 10 cm from the axis of rotation, by what factor are the terminal speeds of the settling particles increased as compared to sedimentation cause by gravity?
a. 3.2 103
c. 800
b. 64
d. 4.0 104
[Ques. 3] Two parallel wires carry the a current I in the same direction. Midway between these wires is a third wire, also parallel to the other two, which carries a current 0.5 I, but in the direction opposite from the first two wires. In which direction are the net forces on the outer wires?
a. Both forces are toward the center wire.
b. Since the net forces are zero, there is no direction.
c. Both forces are away from the center wire.
d. Both forces on the two wires are in the same direction in space.
[Ques. 4] Spherical particles of density 3.0 g/cm3 are shaken in a container of water (viscosity = 1.0 10-3 Ns/m3). The water is 8.0 cm deep and is allowed to stand for 30 minutes. What is the radius of the largest particles still in suspension at that time?
a. 4.5 10-6 m
c. 2.6 10-6 m
b. 9.0 10-6 m
d. 5.6 10-6 m
[Ques. 5] A beam of electrons is sent in the positive x direction in a region with a uniform magnetic field B in the positive y direction and a uniform electric field E in the positive z direction. At which of the following speeds would the electrons be deflected in the positive z direction?
a. v = E/B
b. There is no speed for which this will happen.
c. v < E/B
d. v > E/B
[Ques. 6] Spherical particles of density 2.0 g/cm3 are shaken in a container of water (viscosity = 1.0 10-3 Ns/m3). The water is 8.0 cm deep and is allowed to stand for 15 minutes. What is the greatest terminal velocity of the particles still in suspension at that time?
a. 0.55 10-5 m/s
c. 4.4 10-5 m/s
b. 1.1 10-5 m/s
d. 8.8 10-5 m/s
[Ques. 7] A circular loop carrying a current of 3.0 A is oriented in a magnetic field of 0.35 T. The loop has an area of 0.24 m2 and is mounted on an axis, perpendicular to the magnetic field, which allows the loop to rotate. What is the torque on the loop when its plane is oriented at a 50 angle to the field?
a. 4.6 Nm
c. 0.076 Nm
b. 0.16 Nm
d. 0.23 Nm
[Ques. 8] A pipe of diameter 4 cm is replaced by one of the same length but of diameter 5 cm. If the pressure difference between the ends of the pipe remains the same, by what factor is the rate of flow of a viscous liquid through it changed?
a. 5.1
c. 2.4
b. 3.4
d. 1.5
[Ques. 9] A circular loop carrying a current of 3.0 A is oriented in a magnetic field of 0.35 T. The loop has an area of 0.24 m2 and is mounted on an axis, perpendicular to the magnetic field, which allows the loop to rotate. If the plane of the loop is oriented parallel to the field, what torque is created by the interaction of the loop current and the field?
a. 0.017 Nm
c. 0.25 Nm
b. 0.084 Nm
d. 5.8 Nm
[Ques. 10] A fluid has a density of 1040 kg/m3 . If it rises to a height of 1.8 cm in a 2.0-mm diameter capillary tube, what is the surface tension of the liquid?
a. 0.046 N/m
c. 0.092 N/m
b. 0.056 N/m
d. 0.11 N/m
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