Assertion : An ideal transformer does not vary the power.
Reason : An transformer is used to step-up or step-down ac voltages.

Options

A. If both assertion ans reason are true ans reaason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion istrue but reason is false.
D. If both assertion and reason are false.

Explanation

To analyze the given question, we will break it down into two parts: the assertion and the reason.

### Step 1: Understanding the Assertion
The assertion states that "An ideal transformer does not vary the power."

- **Explanation**: An ideal transformer operates on the principle of conservation of energy. This means that the power input to the transformer (in the primary coil) is equal to the power output (in the secondary coil). Therefore, for an ideal transformer, power remains constant, which supports the assertion.

### Step 2: Understanding the Reason
The reason states that "A transformer is used to step-up or step-down AC voltages."

- **Explanation**: This statement is true. Transformers are designed to either increase (step-up) or decrease (step-down) the voltage levels of alternating current (AC). However, this function of the transformer does not affect the power; it merely changes the voltage and current levels while keeping the power constant.

### Step 3: Evaluating the Relationship Between Assertion and Reason
Now, we need to determine if the reason provided is a correct explanation for the assertion.

- **Analysis**: While both statements are true, the reason does not explain why the assertion is true. The assertion is about the constancy of power in an ideal transformer, while the reason discusses the voltage transformation capability of transformers. Therefore, the reason does not provide a correct explanation for the assertion.

### Conclusion
Based on the analysis:
- The assertion is true: An ideal transformer does not vary power.
- The reason is true: A transformer is used to step-up or step-down AC voltages.
- However, the reason does not correctly explain the assertion.

Thus, the correct answer is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion.

### Final Answer
Both assertion and reason are true, but the reason is not the correct explanation of the assertion.

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