Answer to Question #180279 in Electricity and Magnetism for tina

Question

why must the test charge qo in the definition of the electric field be vanishingly small?

Answer 1

Answer

According to Electrostatics the test charge is a vanishingly small positive charge which can be used to find the presence of an electric field.

The test charge( almost we use positive.) should be as much as small possible that is why which doesn't affect the electric field due to the source charge.

The electric charge that produces the electric field is called a source charge. So we use smaller charge as test charge.