Question

In an ideal step up transformer, the number of turns in primary coil and secondary coil are 100 and 200 respectively. If output current is found to be 5A, then input current will be ______.

• A. 2.5 A
• B. 100 A
• C. 5.0 A
• D. 10 A

Hint:

A "Step-up" transformer steps up the \textbf{voltage} but steps down the \textbf{current}. So, the input current must be higher than the output current.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
In an ideal transformer, input power equals output power ($V_p I_p = V_s I_s$). This means the current is inversely proportional to the number of turns.
Step 2: Formula Application:
$\frac{I_p}{I_s} = \frac{N_s}{N_p}$
Step 3: Explanation:
Given: $N_p = 100, N_s = 200, I_s = 5$ A. $$\frac{I_p}{5} = \frac{200}{100} \implies \frac{I_p}{5} = 2 \implies I_p = 10 \text{ A}$$
Step 4: Final Answer:
The input current is 10 A.