What are the magnetic lines of force? Give their important properties.

Explanation

### Step-by-Step Solution:

**Step 1: Define Magnetic Lines of Force**
Magnetic lines of force are defined as a set of imaginary lines that are drawn around a magnet. These lines represent the direction of the magnetic field and the path that a test magnet would follow if it were placed in the field and allowed to move freely. Specifically, the tangent to these lines at any point indicates the direction of the magnetic field at that point.

**Step 2: Describe the Origin and Termination of Magnetic Lines of Force**
Magnetic lines of force originate from the North Pole of a magnet and merge at the South Pole. This means that outside the magnet, the lines flow from the North Pole to the South Pole.

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