In a step - down transformer the input voltage is `22kV` and the output voltage is `550V` The ratio of the number of turns in the secondary to that in the primary is .

Options

A. `1:20`
B. `20:1`
C. `1:40`
D. `40:1`

Explanation

To find the ratio of the number of turns in the secondary (Ns) to the number of turns in the primary (Np) of a step-down transformer, we can use the relationship between the voltages and the number of turns in the transformer.

### Step-by-Step Solution:

1. **Identify the given values**:
- Input voltage (Primary voltage, Vp) = 22 kV = 22,000 V
- Output voltage (Secondary voltage, Vs) = 550 V

2. **Use the transformer equation**:
The relationship between the primary and secondary voltages and the number of turns is given by the formula:
\[ \frac{V_s}{V_p} = \frac{N_s}{N_p} \]
where:
- Vs = Secondary voltage
- Vp = Primary voltage
- Ns = Number of turns in the secondary
- Np = Number of turns in the primary

3. **Substitute the known values into the equation**:
\[ \frac{550}{22000} = \frac{N_s}{N_p} \]

4. **Calculate the left side of the equation**:
\[ \frac{550}{22000} = \frac{1}{40} \]
This means that:
\[ \frac{N_s}{N_p} = \frac{1}{40} \]

5. **Conclusion**:
The ratio of the number of turns in the secondary to that in the primary is:
\[ \frac{N_s}{N_p} = \frac{1}{40} \]

### Final Answer:
The ratio of the number of turns in the secondary to that in the primary is \( \frac{1}{40} \).

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