Maxwell in his famous equations of electro-magnetism introduced the concept of

Options

A. ac current
B. displacement current
C. impedance
D. reactance

Answer

To solve the question regarding the concept introduced by Maxwell in his equations of electromagnetism, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Maxwell's Equations**:
Maxwell's equations consist of four fundamental equations that describe how electric and magnetic fields interact. They are:
- Gauss's Law for Electricity: \(\nabla \cdot \mathbf{E} = \frac{\rho}{\epsilon_0}\)
- Gauss's Law for Magnetism: \(\nabla \cdot \mathbf{B} = 0\)
- Faraday's Law of Induction: \(\nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}}{\partial t}\)
- Ampère-Maxwell Law: \(\nabla \times \mathbf{B} = \mu_0 \mathbf{J} + \frac{1}{c^2} \frac{\partial \mathbf{E}}{\partial t}\)

2. **Identify the Key Concept**:
Among these equations, the Ampère-Maxwell Law is particularly important. Maxwell modified the original Ampère's Law by adding a term that accounts for changing electric fields, which he termed "displacement current".

3. **Define Displacement Current**:
The displacement current is defined as:
\[ I_d = \epsilon_0 \frac{\partial E}{\partial t} \]
This term is crucial because it allows for the continuity of current in situations where electric fields change over time, even in the absence of conduction current.

4. **Conclusion**:
Therefore, the concept introduced by Maxwell in his equations of electromagnetism is the **displacement current**. This concept is fundamental in understanding electromagnetic waves and the behavior of electric and magnetic fields in various situations.

### Final Answer:
Maxwell introduced the concept of **displacement current** in his equations of electromagnetism.

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