Question

Magnetic lines of forces determines:
A. The shape of the magnetic field
B. Only the direction of the magnetic field
C. Only the relative strength of the magnetic field
D. Both the direction and the relative strength of the magnetic field

Answer 1

Hint Curved lines used to represent a magnetic field, drawn such that the number of lines relates to the magnetic field's strength at a given point and the tangent of any curve at a particular point is along the direction of magnetic force at that point.

Complete Step by step solution
A magnetic field is a vector field in the neighborhood of a magnet, electric current, or changing electric field, in which magnetic forces are observable. A magnetic field is produced by moving electric charges and intrinsic magnetic moments of elementary particles associated with a fundamental quantum property known as the spin. Magnetic field and electric field are both interrelated to each other and are components of the electromagnetic force, one of the four fundamental forces of nature.
The magnetic field at any point in space is a vector quantity. This means there is a direction associated with the field as well as a field strength.
The direction of the magnetic lines of force can be thought of as the direction of the magnetic field. The length of the magnetic lines of force can be thought of as the strength of the field, i.e., the closer the lines, the stronger the field.
Hence, the magnetic force lines determine both the direction as well as relative strength of the magnetic field.

Option (D) is correct.

Note General Properties of Magnetic Lines of Force
1. Magnetic lines of force have a number of important properties, which include:
2. They seek the path of least resistance between opposite magnetic poles. In a single bar magnet as shown to the right, they attempt to form closed loops from pole to pole.
3. They never cross one another.
4. They all have the same strength.
5. Their density decreases (they spread out) when they move from an area of higher permeability to an area of lower permeability.
6. Their density decreases with increasing distance from the poles.
7. They are considered to have direction as if flowing, though no actual movement occurs.
8. They flow from the south pole to the north pole within a material and north pole to south pole in air.