Finding impedance of rlc parallel ckt

[umed9]

in most of the books i have seen that while finding an impedance for an parallel RLC circuit first they find the individual admittance of each of the element the after summation of these they take reciprocal to find the impedance
why is it done like that can't we find the impedance in a normal way of finding resistance in parallel circuit

 

[umed9]

the result does comes different by two methods

 

[berkeman]

in most of the books i have seen that while finding an impedance for an parallel RLC circuit first they find the individual admittance of each of the element the after summation of these they take reciprocal to find the impedance
why is it done like that can't we find the impedance in a normal way of finding resistance in parallel circuit

the result does comes different by two methods

Can you show us how you get two different results using the two different methods? I would not expect that...

 

[meBigGuy]

If you add the admittance and convert to impedance you will get the same result as working out the impedance of 3 parallel elements. Just do the math both ways with Z1, Z2, and Z3 and if they don't agree, do it again until you find the math error. 1/((1/Z1) + (1/Z2) + (1/Z3)) = Zt and the long form for Z1||Z2||Z3 = Zt where Z1||Z2 is (Z1*Z2)/(Z1+Z2)