Question

Strength of magnetic field is defined as

• A. Number of field lines passing normally through a unit surface
  
• B. Electric field lines passing the loop
  
• C. Current through surface
  
• D. Number of electrons passing a specific point per unit time

Answer 1

The correct option is A

Number of field lines passing normally through a unit surface

In a magnetic field we draw lines of force for our understanding about the direction of the field. They are imaginary and don't have a real existence. The stronger the field greater is the number of lines of force. Field lines of force are crowded at the region of strong magnetic field. The number of lines of force passing normally through a given surface area is known as magnetic flux. The magnetic flux per unit area is known as magnetic field. Therefore the magnetic field intensity or strength can be defined as the number of lines of force passing normally through a unit surface area.