Question

Define the magnetic moment of a current-carrying coil. Write its SI unit.

Hint:

The magnetic moment is a vector quantity, pointing normal to the plane of the coil, and it depends on both the current and the area of the coil.

Answer 1

1. Magnetic Moment of a Current-Carrying Coil:

The magnetic moment (\( \mu \)) quantifies the strength and orientation of a current-carrying coil's magnetic field. It is defined as the product of the current \( I \) and the coil's area \( A \), with its direction normal to the coil's plane.

The magnetic moment is calculated using the formula:

\[ \mu = I \cdot A \]

Where:

• \( I \): Current in amperes (A).
• \( A \): Coil area in square meters (m²).

2. Direction of Magnetic Moment:

The right-hand rule determines the direction of the magnetic moment vector. Curl the fingers of your right hand in the direction of the current; your thumb indicates the direction of the magnetic moment.

3. SI Unit of Magnetic Moment:

The SI unit for magnetic moment is the ampere-square meter (A·m²), derived from the units of current (amperes) and area (square meters).

4. Summary:

• Magnetic moment (\( \mu \)) equals \( I \cdot A \).
• The SI unit is ampere-square meter (A·m²).