Define fuel cell?

Explanation

### Step-by-Step Solution:

1. **Definition of Fuel Cell**: A fuel cell is a device that converts the chemical energy from a fuel directly into electricity through a chemical reaction, typically involving hydrogen and oxygen.

2. **Process of Energy Conversion**: In a fuel cell, the combustion of a fuel (like hydrogen) occurs in the presence of an oxidizer (like oxygen). This reaction produces heat and water as byproducts.

3. **Electricity Generation**: The heat produced during the combustion process is then converted into electrical energy. This conversion is efficient and allows for the continuous generation of electricity as long as fuel is supplied.

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