This is the simplest of the simplest - just a resistor and an (AC - to let you see what's going on better) voltage source. It also calculates POWER and RMS voltage, current and power - check these by hand-calculation to confirm your understanding. Remember that RMS stands for Root Mean Square - so:-
- Figure out what the squared V, I or P is over one cycle
- Take the mean of that
- Take the square root of that ... you now have your RMS thing.