Transformation of alternating current formula

Transformation of alternating current formula

1. DC passive branch: I = ± U / R
Where: u --- branch terminal voltage (V)
------I --- branch current (a)
------R --- branch resistance (Ω)
------± - - - U and I take the + sign in the same direction, otherwise take the - sign
2. Conductor resistance R = L * P / S (Ω)
Where: R -- conductor DC resistance (Ω)
------L -- conductor length (m)
------S --- conductor carrying area (CM)
------ρ -- resistivity of conductor (Ω. Cm / M)
P=I*U=I*I*R=U*U/R
Where: P -- power (W)
------U -- voltage (V)
------I -- current (a)
------R -- Resistance (Ω)
When I is constant (resistance in series), P is proportional to R
When u is constant (resistance in parallel), P is inversely proportional to R
Communication formula:
Positive AC voltage
U=Umsin(ωt+τu)
Where: U -- voltage instantaneous value (V)
------Um - maximum voltage (V)
------Tau u-angular frequency (rad / s)
Positive current
Imsin(ωt+τi)
Where: u --- voltage instantaneous value (V)
------Um -- maximum voltage (V)
------τ U - initial phase angle of current (RAD)
Write these first

What are the formulas for calculating resistance in alternating current

In AC circuit, the concept of pure resistance becomes more vague, which is often replaced by inductive reactance, capacitive reactance, impedance and effective resistance. The original intuitive algebraic sum relation is also replaced by the abstract vector sum relation

What is em equal to in sine alternating current expression?
It seems to be equal to the multiplication of four quantities

In the expression of sine alternating current, EM is the amplitude of electromotive force

Among the 50 bunches of flowers, there are 16 bunches of roses, 15 bunches of Calla, 21 bunches of white orchids, 7 bunches of roses and calla, 8 bunches of Calla and white orchids, 10 bunches of roses and white orchids, and 5 bunches of flowers, including roses, Calla and white orchids （　　）
A. 17B. 18C. 19D. 20

There were 7-5 = 2 bunches only containing rose and calla, 8-5 = 3 bunches only containing Calla and Cymbidium, 10-5 = 5 bunches only containing rose and Cymbidium, 16-2-5-5 = 4 bunches only containing calla, 15-2-3-5 = 5 bunches only containing Cymbidium, 21-3-5-5 = 8 bunches only containing rose, Calla and Cymbidium