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The voltage and current in a circuit are given by
v = 10 sin (ωt – π/6)
i = 10 sin (ωt + π/6)
The power consumed is given as
100 Watt
50 Watt
86.6 Watt
25 Watt
25 Watt
Given: Voltage v = 10 sin(ωt - π/6) and Current i = 10 sin(ωt + π/6).
Voltage v = 10 sin(ωt - π/6) and Current i = 10 sin(ωt + π/6).
P=VrmsIrmscos(ϕ)
Identify peak values and phase angles
From the given equations, the peak voltage Vm=10 V and peak current Im=10 A · The phase angles are θv=−π/6 and θi=π/6.
Vm=10,Im=10,θv=−30°,θi=30°
Calculate the phase difference
The phase difference ϕ between voltage and current is given by ϕ=θi−θv.
ϕ=30°−(−30°)=60°
Calculate RMS values
The RMS values are derived from peak values as Vrms=Vm/2 and Irms=Im/2.
Vrms=210,Irms=210
Calculate the power
Substitute the values into the average power formula P=VrmsIrmscos(ϕ), where cos(60°)=0.5.
P=210×210×cos(60°)=2100×0.5=25 W
D is correct because the calculated average power using RMS values and the phase difference of 60° results in 25 Watts.
This concept of power factor cos(ϕ) is essential in Electrical Machines and Power Systems, specifically for determining active, reactive, and apparent power in AC circuits.