A step up transformer operates on a `230 V` line and a load current of 2 ampere. The ratio of the primary and secondary windings is `1 : 25`. What is the current in the primary?

Options

A. 12.5 A
B. 50 A
C. 8.8 A
D. 25 A

Explanation

To find the current in the primary of the transformer, we can use the transformer equations that relate the voltages and currents in the primary and secondary coils.

### Step-by-Step Solution:

1. **Identify Given Values**:
- Voltage in the primary (V1) = 230 V
- Load current in the secondary (I2) = 2 A
- Ratio of primary to secondary windings (N1:N2) = 1:25

2. **Use the Transformer Equation**:
The transformer equations state that:
\[ \frac{V1}{V2} = \frac{N1}{N2} = \frac{I2}{I1} \]
where:
- V1 = Primary voltage
- V2 = Secondary voltage
- N1 = Number of turns in the primary winding
- N2 = Number of turns in the secondary winding
- I1 = Current in the primary winding
- I2 = Current in the secondary winding

3. **Calculate the Secondary Voltage (V2)**:
Since we know the ratio of the windings (N1:N2 = 1:25), we can express V2 in terms of V1:
\[ \frac{N1}{N2} = \frac{1}{25} \implies V2 = V1 \times \frac{N2}{N1} = 230 \times 25 = 5750 \text{ V} \]

4. **Relate the Currents Using the Transformer Equation**:
From the transformer equation, we have:
\[ \frac{I2}{I1} = \frac{N1}{N2} \implies \frac{2}{I1} = \frac{1}{25} \]

5. **Solve for I1**:
Rearranging the equation gives:
\[ I1 = 2 \times 25 = 50 \text{ A} \]

6. **Conclusion**:
The current in the primary winding (I1) is 50 A.

### Final Answer:
The current in the primary is **50 A**.