# What Does Current Lead Or Lag From Voltage Mean In Practical Terms?

if voltage has a value of 10 and current has 5 and lead or lag of 2 seconds then,
If at t=0 voltage is crossing point A(say)
then at t=(0+2) current will reach A
Provided the waveform is linear (magnitude constant)

other wise with time the magnitude will vary

If volt lead current ,volt will reach A fast
If volt lag current ,volt will reach A later

By reaching I mean Its situation in a wave, Where the waveform is a path for progressing
thanked the writer.
Jeff Anderson commented
In practical terms, take how a utility company charges its customers:

Complex power equation S = P + jQ.

The utility charges by apparent power |S| = SQT(P^2 + Q^2) [VA]. P is the average power [watts] or real portion of complex power. Q is the reactive [vars] or imaginary portion.

P is the useful output of the energy-converting device. The apparent power represents the volt-amp capacity to supply the average power.

Think in terms then of power factor pf = cos(theta_v - theta_i). Theta_v - theta_i is the lead or lag.

A pf != 1 (Q != 0) the VA capacity required by the device is larger than the average power used by the device. That make for a higher utility bill! 