Assertion (A): If the number of turns of a coil is increased, it becomes more difficult to push a bar magnet towards the coil.
Reason (R): The difficulty faced is according to Lenz's law.

Options

A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is NOT the correct explanation of A
C. A is true but R is false
D. A is false and R is true

Explanation

To analyze the given assertion and reason, we will break down the concepts involved step by step.

### Step 1: Understanding the Assertion
The assertion states that if the number of turns of a coil is increased, it becomes more difficult to push a bar magnet towards the coil.

- **Explanation**: When a bar magnet is pushed towards a coil, it induces a current in the coil due to the changing magnetic field. According to Faraday's law of electromagnetic induction, the induced electromotive force (emf) in the coil is proportional to the rate of change of magnetic flux through the coil.

### Step 2: Effect of Increasing the Number of Turns
When the number of turns (N) in the coil is increased, the total magnetic flux linkage increases.

- **Explanation**: The magnetic flux (Φ) through the coil is given by the formula:
\[ Φ = N \cdot B \cdot A \]
where \(B\) is the magnetic field strength and \(A\) is the area of the coil. Increasing \(N\) increases the total flux linkage, which leads to a greater induced emf when the magnet is moved.

### Step 3: Understanding the Reason
The reason states that the difficulty faced is according to Lenz's law.

- **Explanation**: Lenz's law states that the direction of the induced current will be such that it opposes the change in magnetic flux that produced it. Therefore, if the magnetic field due to the bar magnet is increasing as it approaches the coil, the induced current will create a magnetic field that opposes this increase. This opposition makes it more difficult to push the magnet towards the coil.

### Step 4: Conclusion
Both the assertion and the reason are correct. The assertion is true because increasing the number of turns increases the induced emf, leading to greater opposition to the motion of the magnet. The reason is also correct as it explains the phenomenon according to Lenz's law.

### Final Answer
Both the assertion (A) and the reason (R) are correct, and R explains A.

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