What is the process for measuring the hysteresis loop of a material like iron?

Process for Measuring the Hysteresis Loop of Materials like Iron

Measuring the hysteresis loop (Hysteresis Loop) of materials such as iron is an important experimental process used to study the magnetic properties of these materials. The hysteresis loop provides crucial information about energy loss, coercivity, and remanence during the magnetization and demagnetization processes. Below is a detailed procedure for measuring the hysteresis loop:

Experimental Equipment

• Power Supply: Provides a stable DC or AC power source.

• Magnetizing Coil: Wrapped around the sample to generate a magnetic field.

• Hall Effect Sensor: Used to measure the magnetic induction B in the sample.

• Ammeter: Used to measure the current I through the magnetizing coil.

• Data Acquisition System: Used to record and process experimental data.

• Sample Holder: Fixes the sample to ensure its position remains stable.

Experimental Steps

Prepare the Sample:

Secure the test material (such as an iron rod or iron sheet) in the sample holder, ensuring its position is stable.

Set Up the Magnetizing Coil:

Wrap the magnetizing coil tightly around the sample, ensuring it is evenly distributed.

Connect the Circuit:

Connect the magnetizing coil to the power supply and ammeter, ensuring the circuit connections are correct.

Place the Hall effect sensor at an appropriate position on the sample to measure the magnetic induction B.

Calibrate the Equipment:

Calibrate the Hall effect sensor and ammeter to ensure accurate measurements.

Initial Demagnetization:

Perform initial demagnetization of the sample to ensure it is in a zero-magnetized state. This can be achieved by applying a reverse magnetic field or heating the sample above its Curie point and then cooling it.

Gradually Increase the Magnetic Field:

Gradually increase the current I through the magnetizing coil and record the magnetic induction B at each current value.Use the data acquisition system to record the corresponding values of I and B.

Gradually Decrease the Magnetic Field:

Gradually decrease the current I through the magnetizing coil and record the magnetic induction B at each current value.Continue recording the corresponding values of I and 

B until the current returns to zero.

Repeat Measurements:

To obtain more accurate data, repeat the above steps multiple times to ensure consistency and reliability of the data.

Plot the Hysteresis Loop:

Use the recorded data to plot the relationship between magnetic induction B and magnetic field strength H.

The magnetic field strength H can be calculated using the following formula: H= NI/L

where:

• N is the number of turns in the magnetizing coil

• I is the current through the magnetizing coil

• L is the average length of the magnetizing coil

Data Analysis

Determine Remanence Br:

Remanence Br is the magnetic induction remaining in the material when the magnetic field strength H is zero.

Determine Coercivity Hc :

Coercivity Hc  is the reverse magnetic field strength required to reduce the magnetic induction B from its positive maximum value to zero.

Calculate Hysteresis Loss:

Hysteresis loss can be estimated by calculating the area enclosed by the hysteresis loop. The hysteresis loss Ph can be expressed using the following formula: P h =f⋅Area of the hysteresis loop where:

f is the frequency (unit: hertz, Hz)

Precautions

• Temperature Control: Maintain a constant temperature during the experiment to avoid the influence of temperature changes on the measurement results.

• Data Recording: Ensure accurate and complete data recording to avoid omissions or errors.

• Equipment Calibration: Regularly calibrate the experimental equipment to ensure the reliability of the measurement results.

By following these steps, the hysteresis loop of materials like iron can be effectively measured, and important magnetic properties can be obtained. These parameters are crucial for material selection and application.