Why are telegraph wires left loose between two poles?

Why is some space left in between two rails?

What happens at the synapse between two neurons?

A diamagnetic substance is placed in the middle between two magnetic poles. If allowed to rotate, explain why the specimen comes to rest with its axis perpendicular to the field.

The distance between two poles of the same height standing on the same plane is 100m.The angles of elevation of the tops of the two poles from a point lying on the line joining the base-points of the poles are found to be 30^@ and 60^@ respectively.Find the heights of the poles and the position of the point.

If the distance between two parallel current carrying wire is doubled. What is the force between them?

Draw a neat diagram of image formated by a concave mirror with an object between the pole and the focus.

Why are pole pices of galvanometer made concave?