Is the work done by a constant voltage source positive or negative when current is opposite to emf?
when current enters positive terminal of voltage source, voltage source charges up , so it gains energy , its power(energy derivative) is positive
shoudnt work done (power integral)be positive?
Work done by the voltage source is negative because it receives energy.
Work done by whatever current source you have, is positive.
Work done on the source is positive. You asked about work done by the source, which is negative.
Separate names with a comma.