Question

The turn ratio is $1:25$. The step-up transformer operates at $230V$ and the current through the secondary is $2A$. Then, current in the primary is

• A. $25A$
• B. $100A$
• C. $50A$
• D. $20A$

Answer 1

The correct option is C

$50A$

Step 1: Given Data

Turn ratio, $N_P:N_S=1:25$

Where $N_P$ is the number of turns in the primary coil and $N_S$ is the number of turns in the secondary coil,

Current through the secondary coil $I_S=2A$

Let the current through the primary coil be $I_P$.

Step 2: Formula Used

$\frac{N_P}{N_S}=\frac{I_S}{I_P}$

Step 3: Calculate the Current

We know that for a step-up transformer,

$$\begin{gathered} \frac{N_P}{N_S}=\frac{I_S}{I_P} \\ \Rightarrow I_P=\frac{N_S}{N_P}\times I_S \\ =\frac{25}{1}\times 2 \\ =50A \end{gathered}$$

Hence, the correct answer is option (C).