How did Oersted demonstrate that a current-carrying wire can affect a compass?

How did Oersted demonstrate that a current-carrying wire can affect a compass?

• A. He observed that a compass deflected near a current-carrying wire
• B. He noticed that a compass deflected near a bar magnet
• C. He heated the wire to see a change in compass direction
• D. He measured electrical resistance while moving the wire

Answer: (B)

A current in a wire creates its own magnetic field, and a compass needle will respond to the total magnetic field present. Oersted saw the compass deflect when a wire carrying current was placed near it, showing that the electric current’s magnetic field can influence the needle. This demonstrated the direct link between electricity and magnetism. The direction of deflection follows the right-hand rule: point the thumb along the current, and the curled fingers show the direction of the magnetic field around the wire. Because the compass aligns with the local magnetic field, the wire’s field changes the needle’s direction, whereas without current there’s no such disturbance. The other ideas—deflection due to a bar magnet, heating the wire, or measuring resistance—don’t capture the specific demonstration that a current itself produces a magnetic field that affects the compass.

A current in a wire creates its own magnetic field, and a compass needle will respond to the total magnetic field present. Oersted saw the compass deflect when a wire carrying current was placed near it, showing that the electric current’s magnetic field can influence the needle. This demonstrated the direct link between electricity and magnetism. The direction of deflection follows the right-hand rule: point the thumb along the current, and the curled fingers show the direction of the magnetic field around the wire. Because the compass aligns with the local magnetic field, the wire’s field changes the needle’s direction, whereas without current there’s no such disturbance. The other ideas—deflection due to a bar magnet, heating the wire, or measuring resistance—don’t capture the specific demonstration that a current itself produces a magnetic field that affects the compass.