In defining electric field due to a point charge, the test charge, the test charge has to be vanishingly small. How this condition can be justified, when we know that charge less than of electron or a proton is not possible.

Explanation

To justify the condition that the test charge must be vanishingly small when defining the electric field due to a point charge, we can follow these steps:

### Step 1: Understanding Electric Field
The electric field (E) due to a point charge (Q) at a distance (r) is defined as the force (F) experienced by a small test charge (q) placed at that point divided by the magnitude of the test charge:
\[ E = \frac{F}{q} \]

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