Question

Two identical transformers \(A\) and \(B\) each with \(\dfrac{N_p}{N_s} = 2\) are connected such that the secondary output obtained from \(A\) is given as the primary input voltage for \(B\). If the primary ac voltage of \(A\) is \(200\) V, then the secondary voltage from \(B\) is

• A. $100$ V
• B. $200$ V
• C. $50$ V
• D. $400$ V
• E. $500$ V

Hint:

For transformers: - Step-down if $\frac{N_p}{N_s} > 1$ - Apply relation sequentially in cascaded transformers

Answer 1

The Correct Option is C

Concept: Transformer relation: \[ \frac{V_p}{V_s} = \frac{N_p}{N_s} \]

Step 1: For transformer $A$.
\[ \frac{V_p}{V_s} = 2 \Rightarrow V_s = \frac{V_p}{2} \] \[ V_s^{(A)} = \frac{200}{2} = 100\ \text{V} \]

Step 2: Use output of $A$ as input of $B$.
\[ V_p^{(B)} = 100\ \text{V} \]

Step 3: For transformer $B$.
\[ V_s^{(B)} = \frac{V_p^{(B)}}{2} = \frac{100}{2} = 50\ \text{V} \]