# B-H Curve Phenomena Of Magnetic Hysteresis With Effect And Loss

## Magnetization curve or BH curve

The graph between the magnetic flux density (B) and magnetic field intensity (H) for the material is called its magnetization or B-H curve. For any magnetic material by increasing magnetic field strength H, magnetic flux density docs not increase linearly but it follows some other path.

By increasing field intensity, flux density increase upto certain point after which increasing the field strength makes very little change in flux density and the material is said to be saturated.

### Information Obtained From B-H curve

1. Flux density always lags with respect to magnetising force.
2. Magnetic hysteresis always results in dissipation of energy.
3. Energy loss is proportional to area of magnetic hysteresis loop, called as, hysteresis loss.

## Magnetic Hysteresis

Question formed from this topic like :

Q: Define Hysteresis effect and hysteresis loss. Explain the necessity of obtaining a B-H loop for a magnetic material.

Hysteresis means lagging behind. The lagging of flux density B behind magnetization force I-I is known as magnetic hysteresis. If the magnetizing force applied to a piece of magnetic material is increased from zero to maximum possible value and then it is reduced to zero, it is found that the new values of B for decreasing values of H lies somewhat above the original values of B for increasing H. When H is zero, B is still present. This effect is called hysteresis, since B lags behind H. The value of B when H is zero, is known as residual magnetism. To reduce residual flux to zero, a certain amount of (H) is required in opposite direction. This is known as coercive force. Now, if H is increased in this negative direction to its maximum value and again decreased, B is again found to be lagging behind H. If this process of applying (+) ve and (—) ve H is continued, then a closed loop will be formed. It is known as Hysteresis Loop. Area of this loop represents the energy lost in magnetizing and demagnetizing the iron piece in one complete cycle. The shape of hysteresis loop depends upon the nature of magnetic material. Following points are noted from hysteresis loop, (l) Flux density B always lags with respect to magnetizing force H. (2) Magnetic hysteresis always results in dissipation of energy and (3) Energy loss is proportional to area of magnetic hysteresis loop and is known as hysteresis loss.