A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnetic is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains horizontal potential energy. the work required to do this comes from

Options

A. the lattice structure of the material of the rod
B. the induced electric field due to the changing magnetic field
C. the magnetic field
D. the current source

Explanation

To solve the problem, let's analyze the situation step by step.

### Step 1: Understanding the Setup
We have a thin diamagnetic rod placed vertically between the poles of an electromagnet. When the current is switched on, a magnetic field is generated between the poles.

**Hint:** Remember that diamagnetic materials are repelled by magnetic fields and tend to move from regions of stronger magnetic fields to regions of weaker magnetic fields.

### Step 2: Behavior of the Diamagnetic Rod
When the magnetic field is applied, the diamagnetic rod experiences a force that pushes it upward. This is because the rod seeks to move to a region where the magnetic field is weaker.

**Hint:** Consider the nature of diamagnetic materials—they are repelled by magnetic fields, which is crucial to understanding their movement in a magnetic field.

### Step 3: Work Done on the Rod
As the rod is pushed upward, it gains potential energy. The work required to move the rod against the gravitational force must come from an external source.

**Hint:** Think about where energy is coming from when the rod is moved. The current source provides energy that can do work on the rod.

### Step 4: Source of Work Done
The work done to push the diamagnetic rod upward comes from the electrical energy supplied by the current source. When the current is switched on, energy is converted from electrical energy to mechanical energy, allowing the rod to move.

**Hint:** Recall the principle of conservation of energy: energy cannot be created or destroyed but can be transformed from one form to another.

### Step 5: Conclusion
Therefore, the work required to push the diamagnetic rod upward against the gravitational force comes from the current source that generates the magnetic field.

**Hint:** Identify the correct option based on the understanding that the current source provides the necessary energy for the work done.

### Final Answer
The work required to do this comes from the current source.