What problem might occur if one should use a large test charge instead of a small test charge to measure an?

Question

electric field

Answer 1

By definition the electric field is defined as

E = limiting value, as q approahes zero, of the ratio (F/q)

So the smaller q gets to 0 the closer the value of E gets to the exact value of the electric field.

The larger q is then the less accurate the ratio is to approximating the electric field.

Answer 2

Your test charge will distort the electric field that you are measuring, and quite possibly could discharge if you aren't careful.