What are diodes and transistors ? For what purpose are they generally used ?

Explanation

### Step-by-Step Solution:

1. **Definition of Diodes**:
- Diodes are semiconductor devices that consist of a combination of P-type and N-type semiconductors.
- The junction between these two types of semiconductors allows current to flow in one direction while blocking it in the opposite direction.

2. **Purpose of Diodes**:
- The primary use of diodes is as rectifiers.
...