Question

A student places a magnetic compass near an insulated copper wire with electric current moving through it. He notices that the compass needle no longer points north.

Which of the following best explains this observation?
A. The magnetic poles that determine north and south reverse periodically.
B. The insulation prevents the compass from detecting Earth's magnetic field.
C. The compass detects the magnetic field produced by the electric current.
D. The copper wire exerts an electrostatic force on the compass needle.

Answer 1

The compass needle is affected by the magnetic field produced by the electric current in the insulated copper wire, causing it to point in a direction other than north, in accordance with electromagnetism principles.

Step-by-step explanation:

The observation that a magnetic compass needle no longer points north when placed near an insulated copper wire with electric current can best be explained by stating that the compass detects the magnetic field produced by the electric current. This is a manifestation of the fundamental relationship between electricity and magnetism discovered by Hans Oersted in 1819. The electric current generates a circular magnetic field around the wire, which interacts with the compass needle, causing it to orient along the direction of this new magnetic field instead of the Earth's magnetic field.

In this scenario, the other options are incorrect because:

• The magnetic poles of Earth do not reverse periodically in such a manner that would affect the compass in this way.
• The insulation on the wire does not prevent the compass from detecting Earth's magnetic field, but rather insulates the wire electrically.
• The wire does not exert an electrostatic force on the compass needle; it's the magnetic field due to the electric current that affects the needle.

Therefore, the correct choice is C. The compass detects the magnetic field produced by the electric current, which is consistent with known principles of electromagnetism.

Answer 2

C. The compass detects the magnetic field produced by the electric current.

Step-by-step explanation:

In 1820, Hans Christian Ørsted discovered that a magnetized needle placed in a direction parallel to an electric conductor was deflected when an electric current circulated through the conductor, evidencing the existence of a magnetic field around any conductor crossed by an electric current.