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. If the number of turns of the secondary coil is 24, then find the number of turns of the primary coil.

Hint:Here we need to know about the transistor and a transformer. The transistor is a semiconductor device that is used to amplify or switch electrical signals and power. The transistor is the basic building block in modern electronics. A transformer is used to transfer the electric energy from one AC circuit to one or more other circuits.

Formula Used:
To formula to find the transformer turns ratio is,
\[\dfrac{{{N_P}}}{{{N_S}}} = \dfrac{{{V_P}}}{{{V_S}}}\] ……….. (1)
Where, \[{N_P}\] is number of turns in primary coil, \[{N_S}\] is number of turns in secondary coil, \[{V_P}\] is primary voltage and \[{V_S}\] is secondary voltage.

Complete step by step solution:
Consider a transistor radio set that requires 12 V (D.C) as the output or secondary voltage. For that, the D.C source operates at 220 V (A.C) which is the primary voltage. If the number of turns of the secondary coil is 24, then we have to count the number of turns of the primary coil.

In order to find the number of turns of the primary coil, we have from the equation (1);
\[\dfrac{{{N_P}}}{{{N_S}}} = \dfrac{{{V_P}}}{{{V_S}}}\]
\[ \Rightarrow {N_P} = \dfrac{{{V_P} \times {N_S}}}{{{V_S}}}\]
Now on substituting the values we get,
\[ \Rightarrow {N_P} = \dfrac{{220 \times 24}}{{12}}\]
\[ \therefore {N_P} = 440\text{ turns}\]

Therefore, the number of turns of the primary coil is found to be 440 turns.

Note:Transformer turns ratio is defined as the number of turns of the primary winding divided by the number of turns of the secondary coil and it provides the voltage required for the secondary winding.