Can the instantaneous power output of an ac source ever be negative ? Can the average power output be negative ?

Explanation

In an RLC circuit, if applied e.m.f. `E = E_(0) sin omega t`, then current developed, `I = I_(0) sin (omega t +- phi)`
Instantaneous power output of the a.c. sorce
`(dW)/(dt) = EI = E_(0) sin omega t I_(0) sin (omega t +- phi)`
It may be negative, because power might be absorbed at some instant. However, average power output over a cycle cannot be negative. It is usually positive or may be zero such as in LC circuit.