Write the expression for energy density of electric field E in free space.

Explanation

To derive the expression for the energy density of the electric field \( E \) in free space, we can follow these steps:

### Step 1: Understand the Concept of Energy Density
Energy density (\( u \)) is defined as the amount of energy stored per unit volume in an electric field.

**Hint:** Remember that energy density is a measure of how much energy is contained in a specific volume.

### Step 2: Relate Energy Density to Capacitance
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