i have attached my circuit and corresponding waveform,i don't even know what my attached circuit is called as.i have 5vrms ac source c, 3v dc source ,some k ohm resistor , all are connected in series.my output waveform look like its shifted down.what operation actually going on there and how the waveform shifted down.Thank you in advance

 

Well it can't be the AC source, and it can't be the resistor, so that leaves.....what exactly?

 

what happens if the battery is reversed?

 

its apparent form that waveform that dc battery making offset ,but i want answer how it does that. Particularly how one way of connecting dc source making offset up and another way of connecting dc source making offset down.Thank you

 

AC changes voltage with time. DC does not change over time. Consider what happens in your series circuit when the AC signal is at a time where it has zero Volts.

 

its apparent form that waveform that dc battery making offset ,but i want answer how it does that. Particularly how one way of connecting dc source making offset up and another way of connecting dc source making offset down.Thank you

With DC voltage source and Vo as in the picture:
V0 = -3V + Vac
If we reverse polarity of DC voltage source, then:
Vo = 3V + Vac