Assertion: when DC ammeter is used to measure current, then it measures average current flowing in the circuit .
Reason : DC ammeter is based on heating effect of current .

Options

A. If both assertion and reason are correct and reason is a correct explanation of the assertion
B. If both assertion and reason are correct but reason is not the correct explanation of assertion
C. If assertion is correct but reason is incorrect
D. If assertion is inncorrect but reason is correct

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states that when a DC ammeter is used to measure current, it measures the average current flowing in the circuit.

- **Explanation**: A DC ammeter is designed to measure the average value of the current over time. In a direct current (DC) circuit, the current is constant, so the average current is equal to the actual current flowing through the circuit.

### Step 2: Understand the Reason
The reason states that a DC ammeter is based on the heating effect of current.

- **Explanation**: While it is true that some devices measure current based on the heating effect (like a hot wire ammeter), a typical DC ammeter operates on the principle of electromagnetic induction. The deflection of the needle in a DC ammeter is proportional to the current flowing through it, which is influenced by the magnetic field and the torque produced by the current in the coil, not primarily by heating.

### Step 3: Conclusion
- The assertion is **correct** because the DC ammeter measures the average current.
- The reason is **incorrect** because the operation of a DC ammeter is not primarily based on the heating effect of current but rather on the electromagnetic principles.

### Final Answer
- The assertion is correct, but the reason is incorrect. Therefore, the answer is: **Assertion is correct, Reason is incorrect.**