An external force moved a positive test charge from A to B where B is closer to the centre of the field. Therefore, the force exerted by the field is from A to B. The text book is saying the work done is negative. But the external force moved the charge against the electric field strength as if a person moves a box to a higher place against the gravitational field strength, so wouldn't the work done by the external force is positive? Or is the force text book is saying is the force by the field? If that is the case, when we are dealing with the work done in moving something in the field, is it usually work done by the field, not the external force?