I have figured out the mesh equations for a circuit but am stuck with the transposition. The equation I havefigured out is
(jwl-j/wc)i2 - ((jwl)x(Vin+(jwL)i2) / Rs+jwL)=0
and I need to get it to equal
i2= (w^2LC) / ((1-w^2LC)Rs+jwL)
Please can you help as it has to be in tomorrow and i'm been dumbfounded for 3 weeks!!
(jwl-j/wc)i2 - ((jwl)x(Vin+(jwL)i2) / Rs+jwL)=0
and I need to get it to equal
i2= (w^2LC) / ((1-w^2LC)Rs+jwL)
Please can you help as it has to be in tomorrow and i'm been dumbfounded for 3 weeks!!
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Hi, Vicky,
I'm afraid I have more questions than answers:
I'm assuming i2 is a single variable, with 2 as a subscript. Is that right?
Are the upper- and lowercase L's and C's the same variables or different ones?
Is there more information somewhere? Your first equation has a Vin term that doesn't look like it should cancel out, but it doesn't appear in the second equation.
Also, remember that j^2 = -1.
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Update: the Vin term still doesn't cancel unless the first equation is missing parens around the denominator (Rs + jωL) like this:
(jωL - j/ωC)i₂ - [(jωL)(Vin + (jωL)i₂) / (Rs + jωL)] = 0
But then, if we multiply both sides by the denominator, we have:
(Rs + jωL)(jωL - j/ωC)i₂ - [(jωL)(Vin + (jωL)i₂)] = 0
Distribute the (jωL) in the square brackets:
i₂(Rs + jωL)(jωL - j/ωC) - Vin(jωL) - i₂(jωL)² = 0
Multiply the first term:
i₂(jωLRs + (jωL)² - jRs/ωC - j²ωL/ωC) - Vin(jωL) - i₂(jωL)² = 0
Replace j² with -1:
i₂[jωLRs - (ωL)² - jRs/ωC + L/C] - Vin(jωL) + i₂(ωL)² = 0
Move the Vin term, then factor i₂:
i₂[jωLRs - (ωL)² - jRs/ωC + L/C + (ωL)²] = Vin(jωL)
Cancel the (ωL)² terms:
i₂[jωLRs - jRs/ωC + L/C] = Vin(jωL)
Multiply both sides by ωC:
i₂[jω²LCRs - jRs + ωL] = Vin(jω²LC)
Factor Rs:
i₂[(jω²LC - j)Rs + ωL] = Vin(jω²LC)
Multiply both sides by j, remembering that j² = -1:
i₂[(-ω²LC + 1)Rs + jωL] = -Vin(ω²LC)
Rearrange:
i₂[(1 - ω²LC)Rs + jωL] = -Vin(ω²LC)
Divide both sides by the term in the square brackets:
i₂ = -Vin(ω²LC) / [(1 - ω²LC)Rs + jωL]
So either your answer or mine is off by a factor of -1.
I'm afraid I have more questions than answers:
I'm assuming i2 is a single variable, with 2 as a subscript. Is that right?
Are the upper- and lowercase L's and C's the same variables or different ones?
Is there more information somewhere? Your first equation has a Vin term that doesn't look like it should cancel out, but it doesn't appear in the second equation.
Also, remember that j^2 = -1.
---------------------
Update: the Vin term still doesn't cancel unless the first equation is missing parens around the denominator (Rs + jωL) like this:
(jωL - j/ωC)i₂ - [(jωL)(Vin + (jωL)i₂) / (Rs + jωL)] = 0
But then, if we multiply both sides by the denominator, we have:
(Rs + jωL)(jωL - j/ωC)i₂ - [(jωL)(Vin + (jωL)i₂)] = 0
Distribute the (jωL) in the square brackets:
i₂(Rs + jωL)(jωL - j/ωC) - Vin(jωL) - i₂(jωL)² = 0
Multiply the first term:
i₂(jωLRs + (jωL)² - jRs/ωC - j²ωL/ωC) - Vin(jωL) - i₂(jωL)² = 0
Replace j² with -1:
i₂[jωLRs - (ωL)² - jRs/ωC + L/C] - Vin(jωL) + i₂(ωL)² = 0
Move the Vin term, then factor i₂:
i₂[jωLRs - (ωL)² - jRs/ωC + L/C + (ωL)²] = Vin(jωL)
Cancel the (ωL)² terms:
i₂[jωLRs - jRs/ωC + L/C] = Vin(jωL)
Multiply both sides by ωC:
i₂[jω²LCRs - jRs + ωL] = Vin(jω²LC)
Factor Rs:
i₂[(jω²LC - j)Rs + ωL] = Vin(jω²LC)
Multiply both sides by j, remembering that j² = -1:
i₂[(-ω²LC + 1)Rs + jωL] = -Vin(ω²LC)
Rearrange:
i₂[(1 - ω²LC)Rs + jωL] = -Vin(ω²LC)
Divide both sides by the term in the square brackets:
i₂ = -Vin(ω²LC) / [(1 - ω²LC)Rs + jωL]
So either your answer or mine is off by a factor of -1.