A transformer changes the voltage

Options

A. without changing the current and frequency
B. without changing the current but changes the frequency
C. without changing the frequency but changes the current
D. without changing the frequency as well as the current

Answer

### Step-by-Step Solution:

1. **Understanding the Transformer**:
- A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. It is primarily used to change the voltage level of alternating current (AC).

2. **Voltage Transformation**:
- The transformer operates on the principle of electromagnetic induction, where a changing magnetic field induces a voltage in a coil of wire. The voltage transformation can be described by the formula:
\[ \frac{V_s}{V_p} = \frac{N_s}{N_p} \]
where \( V_s \) is the secondary voltage, \( V_p \) is the primary voltage, \( N_s \) is the number of turns in the secondary coil, and \( N_p \) is the number of turns in the primary coil.

3. **Current Transformation**:
- Along with voltage, the current also changes in the transformer according to the formula:
\[ \frac{I_p}{I_s} = \frac{N_s}{N_p} \]
where \( I_p \) is the primary current and \( I_s \) is the secondary current. This indicates that if the voltage increases, the current decreases and vice versa.

4. **Frequency Consideration**:
- It is crucial to note that the transformer does not change the frequency of the alternating current. The frequency remains constant regardless of the changes in voltage and current.

5. **Conclusion**:
- Therefore, a transformer changes the voltage and the current, but it does not change the frequency of the alternating current. The correct answer to the question is that a transformer changes the voltage without changing the frequency.

### Final Answer:
A transformer changes the voltage without changing the frequency.

---