Magnetic Field Due to Current in a Loop (Or Circular Coil)

When an electric current passes through a straight conductor, it produces a magnetic field in the form of concentric circles around it. When the conductor is bent into a circular loop, the nature of the magnetic field changes.

Concept of Magnetic Field in a Circular Loop:

• Each small segment of the loop acts as a current-carrying conductor, producing circular magnetic field lines around it. The field lines near the wire are concentric circles.
• At the centre of the loop, the field lines from all segments combine, creating a nearly uniform magnetic field.
• The direction of the magnetic field at the center is determined by the Right-Hand Thumb Rule: If the fingers of the right hand curl in the direction of current flow through the loop, the thumb points in the direction of the magnetic field at the center.
• If the wire is wound into n turns, the total magnetic field at the centre becomes n times stronger than that of a single loop.

Experimental Verification:

• Iron Filings Experiment: Iron filings placed on a cardboard sheet over the loop arrange themselves along the magnetic field lines, visually representing the field pattern.
• Magnetic Needle Test: A magnetic needle placed at different positions aligns along the field lines, showing the direction of the magnetic field.
• Reversing the Current: When the battery connection is reversed, the direction of the magnetic field also reverses, confirmed by the deflection of the magnetic needle.

Magnetic field produced by a current through a loop of conducting wire