In Chapter 18 it throws into the mix v(sub)A in discussing capacitive voltage v(sub)c and capacitive current i(sub)c. V(sub)A is applied voltage from the power source but what is v(sub)A?

EDIT: or is it an errata?

 

OK I think I found the answer. Lower case v or i indicates the instantaneous value of a variable as V voltage and I current are in AC voltage.

 

In Chapter 18 it throws into the mix v(sub)A in discussing capacitive voltage v(sub)c and capacitive current i(sub)c. V(sub)A is applied voltage from the power source but what is v(sub)A?

EDIT: or is it an errata?

A common convention is that upper case variables are used for DC values while lower case variables are used to time-varying values. Without seeing a screenshot of the actual use, what my mind brings to mind is that the power source is applying a time-varying signal in which case it would be v_A(t) and the V_A wouldn't be used at all (unless it is representing a phasor). But the specific context might make it meaningful to use both.

 

Yes it is right along with phasors and discussing v lagging i by 90 degrees and displaying both sinusoidal and phasor descriptions. I found it all the way back in the first chapter in a footnote to a chart. It was the sudden use as a time variable for AC that threw me. Got it now. Thx