In a magnetic circuit, when magnetic flux is passing across the air gap, then effective area of the gap increases and magnetic flux density decreases in the gap. This effect is known as ________.

1.) Magnetic fringing

• The effective area of the air gap in a magnetic circuit increases and the magnetic flux density decreases as the magnetic flux passes through the air gap, is known as "Fringing".
• Fringing occurs because the magnetic lines of force tend to spread out or "fringe" when they cross the air gap in a magnetic circuit.
• Fringing is particularly significant in magnetic circuits with relatively large air gaps or where the air gap length is comparable to the dimensions of the core. It can impact the performance of devices like transformers, inductors, and electromagnets, often requiring compensation in design calculations.
   

2.) Magnetic hysteresis

•  All ferromagnetic materials exhibit the phenomena of hysteresis. 
• Magnetic Hysteresis refers to the lag between the change in magnetization (B) of a ferromagnetic material and the external magnetic field (H) applied to it. This phenomenon is observed when a magnetic material is subjected to a cycle of magnetization and demagnetization.
   

3.) Magnetic leakage

• Magnetic leakage refers to the phenomenon where some of the magnetic flux generated by a magnetic circuit does not follow the intended path but instead "leaks" into surrounding areas. This leakage flux does not contribute to the useful work of the device and can affect the efficiency and performance of magnetic devices like transformers, inductors, and electric motors.
   

4.) Magnetising force

• Magnetization is a measure of how a material responds to an applied magnetic field as well as how the material changes the magnetic field.