A test charge is a hypothetical point charge used to measure the electric potential energy at a particular point in an electric field. It is considered to be immobile and does not affect the electric field or the surrounding charges.
The test charge is typically chosen to have a very small magnitude, such as 1 Coulomb or 1 electron, in order to minimize its impact on the electric field and accurately measure the potential energy at a specific point.
The test charge is considered immobile because it is used solely for measuring the potential energy at a specific point and does not actually move or interact with the surrounding charges in the electric field.
Yes, the test charge can be replaced with a different charge in electric potential energy calculations. However, the value of the potential energy at a specific point may change depending on the magnitude and location of the new charge.
The use of a test charge is limited to situations where the electric field is uniform and the test charge is small enough to not significantly alter the field. In more complex electric fields, the potential energy must be calculated using integrals or other methods.