In a step-down transformer input voltage is 200 volts and output voltage 5 volt. The ratio of nubmer of turns in it will be -

Options

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

Explanation

To solve the problem of finding the ratio of the number of turns in a step-down transformer, we can follow these steps:

### Step 1: Understand the relationship in a transformer
In a transformer, the relationship between the number of turns in the primary coil (Np) and the number of turns in the secondary coil (Ns) is given by the formula:

\[ \frac{N_p}{N_s} = \frac{V_p}{V_s} \]

where \( V_p \) is the primary voltage and \( V_s \) is the secondary voltage.

### Step 2: Identify the given values
From the problem, we have:
- Input voltage (\( V_p \)) = 200 volts
- Output voltage (\( V_s \)) = 5 volts

### Step 3: Substitute the values into the formula
Now, we can substitute the given values into the formula:

\[ \frac{N_p}{N_s} = \frac{200}{5} \]

### Step 4: Calculate the ratio
Now, we perform the division:

\[ \frac{200}{5} = 40 \]

Thus, we have:

\[ \frac{N_p}{N_s} = 40 \]

### Step 5: Express the ratio
This means that the ratio of the number of turns in the primary coil to the number of turns in the secondary coil is:

\[ N_p : N_s = 40 : 1 \]

### Conclusion
The ratio of the number of turns in the step-down transformer is 40:1.

---