Lines of force are imaginary, can they have any practical use?

Body can NOT have

Magnetic lines of force are

Two lines of force due to a bar magnet

Magnetic flux is defined as number of magnetic lines of forces passing through a given area, such that angle between the lines of forces and surface is

Choose the corect options. Magnetic flux is defined as number of magnetic lines of forces passing through a given area such that angle between the lines of forces and surface is

What is thermal stress? Give an example of disadvantages of thermal stress in practical use?

Assertion: Basic difference between an electric line and magnetic line of force is that former is discontinuous and the latter is continuous or endless. Reason: No electric lines of force exist inside a charged body but magnetic lines do exist inside a magnet.

The tangential force per unit length of an imaginary line drwan on the free surface of a liquid, is

Answer the following in short : What are the practical uses of a magnet ?

Write the answer in your words : What are the practical uses of a magnet ?