What is the basic cause of induced emf?

Explanation

### Step-by-Step Solution

1. **Understanding Induced EMF**:
- Induced EMF (Electromotive Force) is a voltage generated in a circuit due to a change in the magnetic environment surrounding it.

2. **Faraday's Law of Electromagnetic Induction**:
- The basic principle governing induced EMF is Faraday's Law, which states that the induced EMF in a closed loop is equal to the negative rate of change of magnetic flux through the loop. Mathematically, it is expressed as:
\[
...