Question

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

Answer 1

Step 1. Given data:

Number of turns in secondary coil is $N_S=24$

Number of turns in primary coil, $N_P=?$

Primary voltage,$V_P=220V$

Secondary voltage, $V_S=12V$

Step 2. Calculating number of turns of primary coil:

We know that for a transformer

$\Rightarrow \frac{N_P}{N_S}=\frac{V_P}{V_S}$

$$\begin{gathered} \Rightarrow N_P=V_P\times \frac{N_S}{V_S} \\ \Rightarrow N_P=220\times \frac{24}{12} \end{gathered}$$

$\because N_P=440$

The number of turns of the primary coil are, $\mathbf{}{\mathit{N}}_{\mathbf{P}}\mathbf{}\mathbf{=}\mathbf{}\mathbf{440}$