Question

In the hysteresis curve the value of magnetization (B) which will be present in a substance when value of magnetizing force (H) is made zero (H = 0) is called as}

• A. coercivity
• B. retentivity
• C. domain
• D. saturation

Hint:

Retentivity represents the 'memory' of magnetization, while coercivity represents the 'resistance' to being demagnetized.

Answer 1

The Correct Option is B

Concept:
A hysteresis loop is the graph between magnetic flux density $B$ and magnetizing field intensity $H$ for a ferromagnetic material. It shows that magnetization lags behind the applied magnetic field.
Step 1: When material is fully magnetized
If the external field $H$ is increased greatly, the material reaches saturation magnetization.
Step 2: Reduce magnetizing field to zero
When the applied magnetic field is reduced back to: \[ H=0 \] the magnetic flux density does not become zero. A certain residual magnetism remains inside the material.
Step 3: Definition of retentivity
The residual magnetic flux density left in the material when: \[ H=0 \] is called: \[ \boxed{\text{Retentivity (or Remanence) \] It measures the ability of a material to retain magnetism.
Step 4: Difference from coercivity
To reduce this residual magnetism to zero, a reverse magnetic field is required. That reverse field is called: \[ \text{Coercivity} \]
Step 5: Final Answer
The quantity represented when magnetism remains after removing external field is: \[ \boxed{\text{Retentivity \] Quick Tip:
Retentivity = magnetism retained at $H=0$; Coercivity = reverse field needed to make $B=0$.