What is a signal?

Explanation

### Step-by-Step Solution:

1. **Definition of Signal**: A signal is defined as a physical quantity that varies with time and can be represented in terms of voltage, current, or electromagnetic waves.

2. **Role of Transducers**: Signals often originate from transducers, which are devices that convert one form of energy into another. For example, a microphone converts sound (acoustic energy) into an electrical signal.

3. **Types of Information**: Signals can carry various types of information, such as pressure, temperature, sound, or frequency. This information is then converted into a signal that can be processed by electrical systems.

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