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slayhy
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A 20.0-mH inductor is connected to a standard electrical
outlet (ΔVrms= 120 V; f = 60.0 Hz). Determine the
energy stored in the inductor at t = (1/180) s, assuming
that this energy is zero at t = 0.
Now when i tried to solve it, this is what i did:
ω = 2∏ f = 2∏(60.0/s) = 377 rad/s
XL = ω L = (377)(0.02)= 7.54 Ω
Irms = ΔVrms/XL = 120 V/7.54 Ω =15.9 A
Imax= √2Irms= √2(15.9 A) = 22.5 A
instantaneous current in the inductor:
i(t)=ΔVmax sin(ωt - ∏/2) / ωL
i(t)=(120√2) sin(377x(1/180) - ∏/2)
i(t)=0.206 A
U= L [i(t)]^2 [sin ωt]^2 / 2
U= 0.02 (0.206)^2 [sin (377x(1/180))]^2 / 2
U= 6.76 x 10^-3 J
But in the book's solution manual it was solved using the instantaneous current in the resistor, which has the formula: i=Imax sinωt
I don't understand why the book used current in the resistor rather than the one in the inductor.
Please help me! I would like an explanation to that.
outlet (ΔVrms= 120 V; f = 60.0 Hz). Determine the
energy stored in the inductor at t = (1/180) s, assuming
that this energy is zero at t = 0.
Now when i tried to solve it, this is what i did:
ω = 2∏ f = 2∏(60.0/s) = 377 rad/s
XL = ω L = (377)(0.02)= 7.54 Ω
Irms = ΔVrms/XL = 120 V/7.54 Ω =15.9 A
Imax= √2Irms= √2(15.9 A) = 22.5 A
instantaneous current in the inductor:
i(t)=ΔVmax sin(ωt - ∏/2) / ωL
i(t)=(120√2) sin(377x(1/180) - ∏/2)
i(t)=0.206 A
U= L [i(t)]^2 [sin ωt]^2 / 2
U= 0.02 (0.206)^2 [sin (377x(1/180))]^2 / 2
U= 6.76 x 10^-3 J
But in the book's solution manual it was solved using the instantaneous current in the resistor, which has the formula: i=Imax sinωt
I don't understand why the book used current in the resistor rather than the one in the inductor.
Please help me! I would like an explanation to that.