Question

Magnetic field is a
A. Vector quantity
B. Scalar quantity
C. Scalar as well as vector quantity
D. Neither vector nor scalar

Answer 1

Hint: Magnetic field is an area in space where an object exhibits a magnetic influence. Now the object can be moving charges or any magnetic material. When we say influence it is quantified in terms of force. And forces are vector quantity.

Complete answer:
Magnetic field is an area in space where an object experiences magnetic influence of another object. Now that another object can be moving charges, any magnetic material or any dynamic electric field. This nature of generation of magnetic field revolutionised the working of many machineries from home to large scale industries. To define a magnetic field we have to mention the intensity/ magnitude of the magnetic field and also its direction. Lines joining points in space of equal magnetic field intensity are similar to electric field lines and the density of these field lines tell the intensity of the magnetic field at that region.
Consider a magnetic needle in a compass. When suspended in free air, it aligns in only one direction at a particular place on earth. Earth possesses its own magnetic field and the field lines extend all around earth for longer distances. So this magnetic field exerts force on the needle and since the needle has its own magnetic field it will align itself with the earth’s magnetic field line at that location. Magnetic field has a polarity similar to the electric field but known as the North Pole and the South Pole. If we change this polarity of the needle (we can assume to change the poles of earth but it is not practically possible for the present state of human civilization, so a simple task is to change the polarity of the magnetic needle by turning it 180 degrees about its rotation axis). We see that in no time it goes back to its original position. Any object experiences forces when placed in a magnetic field. Just like a vector quantity, a magnetic field is described with both magnitude and direction. Thus the magnetic field is vector quantity.

Note: Magnetic field is unlike its electric counterpart electric field. Electric field is defined as the force per unit charge but, magnetic field is defined by magnetic field intensity with magnetic moments. Opposite charges can exist independently, opposite poles existing independently is an abstract concept to understand electric field behaviour.