Question

An ideal transformer has $50$ turns in its primary winding and $25$ turns in its secondary winding. If the current in the secondary winding is $4\text{A}$, then the value of current (in $\text{A}$) in the primary winding if a $200\text{V}AC$ is applied across it is :(Integer only)

Answer 1

Given:
Number of turns in primary winding, $N_P=50$
Number of turns in secondary winding, $N_S=25$

Current in the secondary winding, $I_S=4\text{A}$

The ratio of turns in primary to secondary winding is,

$\frac{N_P}{N_S}=\frac{2}{1}$

Therefore, the given transformer is a step-down transformer.

By transformer equation we have,

$\frac{E_S}{E_P}=\frac{N_S}{N_P}$

$\Rightarrow E_S=\frac{N_S}{N_P}\times E_P$

$\Rightarrow E_S=\frac{25}{50}\times 200=100\text{V}$

Power equation of ideal transformer gives,

$E_S{I}_S=E_P{I}_P$

$I_P=\frac{E_S{I}_S}{E_P}=\frac{100\times 4}{200}=2\text{A}$

Hence, $2$ is the correct answer.