In a step up transformer, if ratio of turns of primary to secondary is `1:10` and primary voltage si `230 V`. If the load current is `2A`. Then the current in primary is

Options

A. 20 A
B. `10A`
C. `2 A`
D. `1 A`

Answer

To find the current in the primary coil of a step-up transformer, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Turns ratio (Np:Ns) = 1:10
- Primary voltage (Vp) = 230 V
- Load current (Is) = 2 A

2. **Calculate the Secondary Voltage (Vs):**
- The turns ratio can be expressed as:
\[ \frac{N_s}{N_p} = \frac{V_s}{V_p} \]
- Given the turns ratio \( \frac{N_p}{N_s} = \frac{1}{10} \), we can find \( V_s \):
\[ \frac{N_s}{N_p} = 10 \implies \frac{V_s}{230} = 10 \]
- Rearranging gives:
\[ V_s = 10 \times 230 = 2300 \text{ V} \]

3. **Use the Power Conservation Principle:**
- In an ideal transformer (assuming 100% efficiency), the power input equals the power output:
\[ V_p \cdot I_p = V_s \cdot I_s \]
- Rearranging for \( I_p \):
\[ I_p = \frac{V_s \cdot I_s}{V_p} \]

4. **Substituting the Known Values:**
- Substitute \( V_s = 2300 \text{ V} \), \( I_s = 2 \text{ A} \), and \( V_p = 230 \text{ V} \):
\[ I_p = \frac{2300 \cdot 2}{230} \]

5. **Calculate \( I_p \):**
- Simplifying gives:
\[ I_p = \frac{4600}{230} = 20 \text{ A} \]

### Final Answer:
The current in the primary coil \( I_p \) is **20 A**.

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