*Question E5B06:
What is susceptance?*  

*Correct Answer is  C: The imaginary part of admittance*  

### AI Response: (may contain errors)  

Susceptance is a concept in electrical engineering that relates to the behavior of AC circuits, particularly in the context of admittance.

### Correct Answer: C - The imaginary part of admittance

- **Explanation**: 
  - Admittance ($Y$) is a measure of how easily a circuit allows current to flow when a voltage is applied. It is the reciprocal of impedance ($Z$) and is expressed as:
  
  $$
  Y = G + jB
  $$
  
  where:
  - $G$ = conductance (real part)
  - $B$ = susceptance (imaginary part)
  
  Thus, susceptance ($B$) represents the imaginary component of admittance, indicating how much reactive power is present in the circuit.

### Why the Other Choices are Incorrect:

- **A: The magnetic impedance of a circuit**  
  - **Explanation**: This choice confuses impedance with susceptance. Impedance ($Z$) is a complex quantity that includes both resistance and reactance, while susceptance specifically refers to the imaginary part of admittance, not impedance.

- **B: The ratio of magnetic field to electric field**  
  - **Explanation**: This choice describes a different concept related to electromagnetic fields, not susceptance. Susceptance does not involve a direct ratio of magnetic to electric fields.

- **D: A measure of the efficiency of a transformer**  
  - **Explanation**: Efficiency in transformers is typically expressed as a ratio of output power to input power, not in terms of susceptance. Susceptance relates to reactive power, not efficiency.

### Summary:
- Susceptance is the imaginary part of admittance, which indicates how a circuit responds to reactive power.
- Remember the relationship between admittance and impedance, as well as the definitions of conductance and susceptance, to help clarify these concepts for the exam.