A common transistor radio set requires 12 V (D.C.) for its operation. The D.C. source is constructed by using a transformer and a rectifier circuit, which are operated at 220 V (A.C.) on standard domestic A.C. supply. The number of turns of secondary coil are 24, then the number of turns of primary are _______.

Concept:

For a transformer we know that :

\(\ \ \frac{N_{P}}{N_{S}} = \frac{V_{P}}{V_{S}}\) ...................(1)

This is the relation between a number of coils and voltage.

Calculation:

Given: 

The number of turns in secondary coil is Ns = 24

Primary voltage, Vp = 220V, Secondary voltage, Vs = 12 V

The number of primary coils is NP =?

Equation (1) can be written as :

  \(\frac{N_{P}}{N_{S}} = \frac{V_{P}}{V_{S}}\)

\(\Rightarrow \frac{N_{P}}{24} = \frac{220}{12}\)

\(\Rightarrow N_{P} = \) 440.

∴ The number of primary coils are = 440