Ferromagnetic Hysteresis Experiment

Experiment Objectives

• To study the hysteresis behavior of a ferromagnetic material.
• To obtain the B–H curve (hysteresis loop) of the given ferromagnetic specimen.
• To determine key magnetic parameters:
• Coercivity (Hc)
• Remanence (Br)
• Saturation magnetization (Bs)
• Energy loss per cycle

Apparatus / Components Required

• Ferromagnetic core (toroidal or rod-shaped).
• Primary coil (excitation winding) with known number of turns (Np).
• Secondary coil (sensing winding) with known number of turns (Ns).
• Signal generator / AC source (low frequency, e.g., 50–200 Hz).
• Shunt resistor (R_shunt) for current measurement.
• RC Integrator circuit (resistor and capacitor).
• Dual-channel CRO or Digital Storage Oscilloscope with X–Y mode.
• Connecting wires, resistors, capacitors.

Theory

When an alternating current flows through the primary coil, a magnetizing field H is produced inside the ferromagnetic core:

H = (N_p · I) / l_m

The magnetic flux density B inside the core is related to the induced emf in the secondary coil according to Faraday’s law:

V_s(t) = –N_s · A · dB/dt

By passing the secondary voltage through an RC integrator, the output voltage becomes proportional to B:

B(t) = (R · C) / (N_s · A) · V_int(t)

On the oscilloscope (X–Y mode), the closed curve obtained is the hysteresis loop of the material:

• The width of the loop (X-axis) → Coercivity (Hc).
• The height of the loop (Y-axis) → Remanence (Br).
• The area of the loop → Energy loss per cycle.