The force experienced by a unit test charge is a measure of the strength of an electric:

an electric field is the answer

The force experienced by a unit test charge is a measure of the strength of an electric field

Electric field strength is the intensity of an electric field at a particular location. The standard unit is the volt per meter (v/m or v. m -1). A field strength of 1 v/m represents a potential difference of one volt between points separated by one meter. A test charge shows the direction of the field. But the "test" charge should be small, since charges generate their own fields, hence they interfere with the external field.

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