The term cos φ in AC power is called:

Solution

Physics sir · 3 steps

Average AC power is Vᵣₘₛ Iᵣₘₛ cut down by cos φ, and that factor gets its name from power.

1. Average power. In an AC circuit the current lags or leads the voltage by a phase angle φ. Averaged over one cycle, the power delivered is:

   P_(avg) = Vᵣₘₛ Iᵣₘₛ cos φ

2. What cos φ does. Vᵣₘₛ Iᵣₘₛ is the apparent power. The factor cos φ tells you what fraction of it is really used up as power. It equals R/Z, running from 1 in a purely resistive circuit down to 0 in a purely inductive or capacitive one.
3. So. Because it decides how much real power is delivered, cos φ is called the power factor, option (b).

The idea to keep. Power factor cos φ = R/Z is the fraction of apparent power VᵣₘₛIᵣₘₛ that does real work. It is 1 for pure R and 0 for pure L or pure C.

Answer from the NTA final answer key. Solution by PrepWiser.