While doing an experiment Neeraj fixed a sheet of white paper on a drawing board. He placed a bar magnet in the centre of it. He sprinkled some iron filings uniformly around the bar magnet. Then he tapped the board gently and observed that the iron filings arranged themselves in a particular pattern.
The lines along which the iron filings align represent ______. It moves from ______

Options

A. Gravitational force, North to South pole
B. Magnetic field lines, South to North pole
C. Gravitational force, South to North pole
D. Magnetic field lines, North to South pole

Answer

### Step-by-Step Solution:

1. **Understanding the Experiment**: Neeraj conducted an experiment by placing a bar magnet on a sheet of white paper and sprinkling iron filings around it. This setup is commonly used to visualize the magnetic field created by the magnet.

2. **Observation of Iron Filings**: When Neeraj tapped the board, the iron filings aligned themselves along specific lines. This behavior occurs because the iron filings become tiny magnets themselves in the presence of the magnetic field, aligning along the field lines.

3. **Identifying the Lines**: The lines along which the iron filings align represent the **magnetic field lines**. These lines are invisible but indicate the direction and strength of the magnetic field around the magnet.

4. **Direction of Magnetic Field Lines**: The magnetic field lines emerge from the **north pole** of the magnet and enter the **south pole**. Therefore, the lines move from the north to the south outside the magnet.

5. **Final Answer**:
- The lines along which the iron filings align represent **magnetic field lines**.
- They move from **north to south**.