Which one of the following units is not that of mutual inductance

Options

A. Henry
B. `"(Weber)"^(-1)`
C. Ohm second
D. Volt second `"(ampere)"^(-1)`

Explanation

To solve the question of which unit is not that of mutual inductance, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Mutual Inductance**: Mutual inductance is a property of two coils where a change in current in one coil induces an electromotive force (EMF) in the other coil. The unit of mutual inductance is the same as that of self-inductance.

2. **Know the Formula for Self-Inductance**: The self-inductance \( L \) is defined as:
\[ L = \frac{E}{\frac{di}{dt}} \]
where \( E \) is the electromotive force (EMF), \( di \) is the change in current, and \( dt \) is the change in time.

3. **Identify Units**:
- The unit of EMF (\( E \)) is Volt (V).
- The unit of current (\( i \)) is Ampere (A).
- The unit of time (\( t \)) is seconds (s).

4. **Derive the Unit of Inductance**:
- From the formula, we can rearrange it to find the unit of inductance:
\[ L = \frac{V}{A/s} = \frac{V \cdot s}{A} \]
- This can also be expressed as:
\[ L = \text{Volt} \cdot \text{second} \cdot \text{Ampere}^{-1} \]

5. **Identify Common Units of Inductance**:
- The derived unit can also be expressed in terms of other known units:
- \( 1 \, \text{Henry} = 1 \, \text{Volt} \cdot \text{second} \cdot \text{Ampere}^{-1} \)
- \( 1 \, \text{Henry} = 1 \, \text{Ohm} \cdot \text{second} \)

6. **List the Units**: The common units of mutual inductance are:
- Henry (H)
- Volt-second per Ampere (V·s/A)
- Ohm-second (Ω·s)

7. **Identify the Incorrect Unit**: The question asks which one of the following units is not a unit of mutual inductance. The unit Weber (Wb) is not a unit of mutual inductance. Therefore, the answer is:
- **Weber (Wb)** is not a unit of mutual inductance.

### Final Answer:
The unit that is not of mutual inductance is **Weber (Wb)**.