Quantity that remains unchanged in a transformer is

Options

A. voltage
B. current
C. frequency
D. none of these

Answer

To solve the question regarding the quantity that remains unchanged in a transformer, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Function of a Transformer**: A transformer is a device used to change the voltage of alternating current (AC) in a circuit. It can either step up (increase) or step down (decrease) the voltage.

2. **Identify the Parameters of a Transformer**: The main parameters involved in a transformer are voltage (V), current (I), and frequency (f). When a transformer operates, it changes the voltage and current according to the turns ratio of the coils.

3. **Recognize the Principle of Conservation**: In a transformer, while the voltage and current can change, there is a principle of conservation that applies to certain quantities.

4. **Frequency Conservation**: The frequency of the alternating current remains unchanged when it passes through a transformer. This is because the transformer operates on the principle of electromagnetic induction, which does not alter the frequency of the input signal.

5. **Conclusion**: Therefore, the quantity that remains unchanged in a transformer is the frequency.

### Final Answer:
The quantity that remains unchanged in a transformer is the **frequency**.

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