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# 1. Which describes the vector calculation of the Biot-Savart law?    a. The length element in...

1. Which describes the vector calculation of the Biot-Savart law?

a. The length element in the direction of the current is crossed into a vector directed from that element toward the point of measurement.
b. The length element in the direction of the current is dotted into a vector directed from that element toward the point of measurement.
c. The magnetic field vector is crossed into a vector directed from a current-length element toward the point of measurement.
d. The magnetic field vector is dotted into a vector directed from a current-length element toward the point of measurement.
e. The magnetic field vector is crossed into a length element in the direction of the current.
f. The magnetic field vector is dotted into a length element in the direction of the current.

2. Which describes the spacing of the magnetic field lines near a long straight wire carrying current?

a. The spacing increases as the distance from the wire increases.
b. The spacing decreases as the distance from the wire increases.
c. The spacing is uniform.

3. We set up two parallel currents in the same direction. Which describes the magnetic force on each wire due to the other wire?

a. The force on each current is in the direction of the current.
b. The force on each current is in the direction opposite that of the current.
c. The force on each current is perpendicular to the current and toward the other current.
d. The force on each current is perpendicular to the current and away from the other current.

4. We set up two parallel currents in the same direction. Which describes the magnetic field set up by current 1 at a point on current 2?

a. The field is in the direction opposite current 2.
b. The field is perpendicular to current 2.
c. The field is in the same direction as current 2.

5. What do we calculate if we integrate length element ds around a full circle?

a. the radius of the circle
b. the area of the circle
c. the circumference of the circle
d. the diameter of the circle

6. In Ampere’s law, when we integrate the magnetic field along a loop, which are summing?

a. the field components that are parallel to the path elements, at every point along the loop
b. the field components that are perpendicular to the path elements, at every point along the loop
c. the magnitudes of the field vectors at every point along the loop

7. Which describes the magnetic field at a point inside a long wire that carries current uniformly across its circular cross-sectional area?

a. The field is directed radially inward.
b. The field is tangent to a circle through the point and concentric with the wire.
c. The field is directed radially outward.

8. Which is true about a solenoid?

a. The internal magnetic field is approximately uniform. The external magnetic field is weak.
b. The magnetic field is approximately uniform both inside and outside the solenoid.
c. The internal magnetic field is weak. The external magnetic field is approximately uniform.

9. In using Ampere’s law for a solenoid as in this section, which is true about the values of the integration parts?

a. The integrations parallel to the length of the solenoid give a zero result; those perpendicular to the length give a nonzero result.
b. The integrations parallel to the length of the solenoid give a nonzero result; those perpendicular to the length give a zero result.
c. The integrations parallel and perpendicular to the length of the solenoid give a zero result.
d. The integrations parallel and perpendicular to the length of the solenoid give a nonzero result.

10. Which describes the magnetic field along the central axis of a current loop?

a. The field is directed along the axis and away from the loop on one side and toward the loop on the other side.
b. The field is directed along the axis and toward the loop on both sides of the loop.
c. The field is directed along the axis and away from the loop on both sides of the loop.
d. The field is perpendicular to the axis.

1. Which describes the vector calculation of the Biot-Savart law?

a. The length element in the direction of the current is crossed into a vector directed from that element toward the point of measurement.

2. Which describes the spacing of the magnetic field lines near a long straight wire carrying current?

c. The spacing is uniform

3. We set up two parallel currents in the same direction. Which describes the magnetic force on each wire due to the other wire?

c. The force on each current is perpendicular to the current and toward the other current.

4. We set up two parallel currents in the same direction. Which describes the magnetic field set up by current 1 at a point on current 2?

b. The field is perpendicular to current 2.

5. What do we calculate if we integrate length element ds around a full circle?

c. the circumference of the circle

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