Magnetic Fields due to Currents

Question 1

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

Answer 1

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

Question 2

Which describes the magnetic field lines near a long straight wire carrying current?

Answer 2

They form concentric circles around the wire, in a plane perpendicular to the wire.

Question 3

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

Answer 3

The spacing increases as the distance from the wire increases.

Question 4

A long straight wire carries current. What is the angle between the direction of the current and the direction of the magnetic field at a point near the wire?

Answer 4

90 degrees

Question 5

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

Answer 5

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

Question 6

If two parallel currents repel each other, which describes the directions of the currents?

Answer 6

They are in opposite directions.

Question 7

Which currents are included in a calculation of Ampere’s law?

Answer 7

only currents that are inside the loop of integration

Question 8

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

Answer 8

the field components that are parallel to the path elements, at every point along the loop

Question 9

Which describes the integration in Ampere’s law?

Answer 9

It is an integration around the circumference of a loop.

Question 10

Which describes the magnetic field of long straight wire that carries current uniformly across its circular cross-sectional area?

Answer 10

The field is maximum at the surface and progressively smaller as you move away from the surface, either toward the center or away from the center.