A student observes that a compass needle deflects when brought near a current-carrying wire. Using your understanding of magnetic fields, explain why this happens.

The correct option is: A current-carrying wire creates a magnetic field that exerts a force on the compass needle.

Step-by-Step Explanation:

1. Understanding the Compass Needle:
A compass needle is a small, lightweight permanent magnet that is free to pivot. Because it is a magnet, it aligns itself with the surrounding magnetic field. Typically, this is the Earth's magnetic field, pointing towards the magnetic north pole.

2. Electromagnetism and Current-Carrying Wires:
When an electric current flows through a conducting wire, it generates a magnetic field around the wire. This fundamental principle of electromagnetism was first discovered by Hans Christian Ørsted. The magnetic field forms concentric circular loops centered on the wire.

3. Interaction of Magnetic Fields:
When the compass is brought near the current-carrying wire, the magnetic field generated by the electric current interacts with the magnetic field of the compass needle. This interaction exerts a magnetic force (or torque) on the compass needle, causing it to deflect from its original orientation and align with the new, stronger local magnetic field produced by the wire.