A coil is suspended in a uniform magnetic field, with the plane of the coil parallel to the magnetic lines of force. When a current is passed through the coil it starts oscillating, It is very difficult to stop. But if an aluminium plate is placed near to the coil, it stops. This is due to :

Options

A. development of air current when the plate is placed
B. induction of electrical charge on the plate
C. shielding of magnetic lines of force as aluminium is a paramagnetic material
D. electromagnetic induction in the aluminium plate give rise to electromagnetic damping

Explanation

To solve the question, we will analyze the situation step by step.

### Step 1: Understand the Setup
A coil is suspended in a uniform magnetic field, and its plane is parallel to the magnetic lines of force. When a current passes through the coil, it generates a magnetic field around it, which interacts with the external magnetic field.

**Hint:** Visualize the setup with a diagram showing the coil and the magnetic field lines.

### Step 2: Current Flow and Oscillation
When the current flows through the coil, it creates a magnetic field that varies with time. This variation in the magnetic field leads to the oscillation of the coil. The oscillation occurs due to the interaction between the magnetic field produced by the coil and the external magnetic field.

**Hint:** Recall how magnetic fields interact with each other and how they can cause motion.

### Step 3: Introducing the Aluminum Plate
When an aluminum plate is placed near the oscillating coil, it affects the behavior of the coil. Aluminum is a good conductor, which means it can allow electric currents to flow through it when exposed to a changing magnetic field.

**Hint:** Consider the properties of conductors and how they respond to magnetic fields.

### Step 4: Electromagnetic Induction
According to Faraday's law of electromagnetic induction, a changing magnetic field through a conductor induces an electromotive force (EMF) in that conductor. When the aluminum plate is placed near the coil, the varying magnetic field from the coil induces an EMF in the aluminum plate.

**Hint:** Remember the relationship between changing magnetic fields and induced EMF.

### Step 5: Lenz's Law
Lenz's law states that the direction of the induced EMF will be such that it opposes the change in magnetic flux that produced it. Therefore, the induced EMF in the aluminum plate will create a magnetic field that opposes the oscillating magnetic field of the coil.

**Hint:** Think about how Lenz's law acts as a form of conservation of energy.

### Step 6: Electromagnetic Damping
The opposing magnetic field created by the induced EMF in the aluminum plate results in a torque that acts against the oscillation of the coil. This effect is known as electromagnetic damping. As a result, the oscillation of the coil is reduced and eventually stops.

**Hint:** Consider how damping forces work in oscillatory systems.

### Conclusion
The oscillation of the coil stops due to electromagnetic induction in the aluminum plate, which creates a damping effect. Therefore, the correct answer to the question is:

**Option D: Electromagnetic induction in the aluminum plate gives rise to electromagnetic damping.**