What is the effect of Frenkel defect on the electrical conductivity of crystalline solids ?

Explanation

### Step-by-Step Solution

1. **Understanding Frenkel Defect**:
- A Frenkel defect occurs when a cation leaves its normal lattice position and occupies an interstitial site within the crystal structure. This defect is more common in ionic solids where the cation is smaller than the anion.

2. **Effect on Crystal Structure**:
- The movement of the cation creates a vacancy in the lattice where the cation was originally located. However, because the cation moves to an interstitial position, the overall density of the crystal remains relatively unchanged.

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