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.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?
by Jake Hertz
by Jake Hertz
by Aaron Carman