How does a transformer perform impedance (Z) matching in electrical circuits?

Can any one please guide me what is actual concept of transformer use for impedence matching ???

A transformer is an impedance reflecting device essentially although you can think of it differentially.

Vpprimary/Iprimary = Vsecondary/Isecondary wich is power transfer, conservation of energy, lay of mother nature

Vprimary/Iprimary = Zprimary, also Vsecondary/Isecondary = Zsecondary, from above V/I = impedance

Volts/turn / Amper-turns = Vprimary/Nprimary / Iprimary*Nprimary = Zprimary/Nprimary^2 (turns squared

Secondary equation follows from primary, fill in the blank.

So then what you get is: Zprimary/Nprimary^2 (turns squared = Zsecondary/Nsecondary^2 (turns squared)

So say you want to match the primary impedance with something connected to the secondary. Say Zprimary = 50 Ohms and Nprimary/Nsecondary = 10, what must the impedance in the secondary be if it is to match the primary 50 Ohms?

Simple: 50 Ohms * (1/10)^2 => 50Ohms * Nseconday^2/Nprimary^2

50 Ohms / 100 = 1/2 Ohm. You can verify this by using Vprimary^/50 = Vsecondary^/(1/2)
If Vprimary is 10V, that makes Vsecondary 1 V, so 100/50 = 2 & 1/ (1/2) = 2

Not rocket science.

Transformer is used for impedance matching as a function of the turns ratio squared. Vacuum tubes have a high impedance - so in order to drive a speaker you need to transform it down to a low impedance so you can get maximum power transfer. Likewise transistors have a low impedance and you sometimes need to transform the impedance up. Again the use of transformers for impedance matching and maximum power transfered from the deivc e to the load.

See Earl's reply for the formulas

another aspect of impedance matching is the TV balun transformer. It converts a balanced signal from the antenna (thru a 300-ohm twin-lead) into a 75-ohm coaxial cable such as RG-6. In order to match the impedances of both devices, both cables must be connected thru a matching transformer with a turns ratio of 2 (such as a 2:1 transformer). In this example, the 75-ohm cable is connected to the transformer side with fewer turns; the 300-ohm line is connected to the transformer side with more turns.