Question

Write the unit of self-inductance.

Hint:

Think about the unit that follows from \(\varepsilon = -L\,dI/dt\); it is named after Joseph Henry.

Answer 1

Step 1: Start from the flux definition.
Self-inductance can also be written as \(L = \dfrac{N\Phi}{I}\), where \(N\Phi\) is the total magnetic flux linkage and \(I\) is the current.

Step 2: Substitute the units of each quantity.
Magnetic flux \(\Phi\) is measured in weber (Wb) and current \(I\) in ampere (A). Therefore
\([L] = \dfrac{\text{weber}}{\text{ampere}} = \text{Wb/A}\).

Step 3: Identify the named unit.
One weber per ampere is defined as one henry (H). A coil has a self-inductance of 1 H if a current changing at 1 A/s induces an EMF of 1 V.

\[\boxed{\text{Unit of self-inductance} = \text{henry (H)}}\]