*Question E5B12:
What is admittance?*  

*Correct Answer is  A: The inverse of impedance*  

### AI Response: (may contain errors)  

Admittance is a concept used in electrical engineering and radio communications to describe how easily a circuit or component allows current to flow. It is particularly important in analyzing AC circuits.

### Correct Answer: A: The inverse of impedance

1. **Why the correct answer is correct:**
   - Admittance ($Y$) is defined as the inverse of impedance ($Z$). Mathematically, this is expressed as:
     $$ Y = \frac{1}{Z} $$
   - Impedance is a measure of how much a circuit resists the flow of alternating current (AC), and admittance measures how easily the current flows.

2. **Why the other choices are incorrect:**
   - **B: The term for the gain of a field effect transistor**
     - This is incorrect because the gain of a field effect transistor (FET) is not referred to as admittance. Gain is typically related to the amplification factor of the transistor.
   - **C: The inverse of reactance**
     - This is incorrect because reactance is only a part of impedance. Admittance is the inverse of the entire impedance, not just the reactance component.
   - **D: The term for the on-impedance of a field effect transistor**
     - This is incorrect because "on-impedance" refers to the resistance when a transistor is conducting, not admittance.

### Additional Information:
- Admittance is measured in siemens (S), whereas impedance is measured in ohms ($\Omega$).
- Admittance can be broken down into two components: conductance ($G$) and susceptance ($B$), where:
  $$ Y = G + jB $$
  - **Conductance ($G$)** is the real part, representing the ability to conduct current.
  - **Susceptance ($B$)** is the imaginary part, representing the ability to store energy in the circuit.

Understanding admittance is crucial for analyzing and designing circuits, especially in RF and AC applications.