Question

Permanent magnets are made of:

• A. High energy hard magnetic material
• B. Ti–Al–V alloy
• C. Commercial iron
• D. Copper–Zinc alloy

Hint:

\textbf{Permanent magnets} require \textbf{hard magnetic materials} like ferrites or rare-earth alloys due to their high coercivity and BH\(_{\text{max}}\).

Answer 1

The Correct Option is A

Step 1: Characteristics of Permanent Magnets
Permanent magnets are materials that retain a significant magnetic field after magnetization. Their performance depends on: - High coercivity (resistance to demagnetization), - High remanence (residual magnetism), - High magnetic energy product (BH\(_{\text{max}}\)). Step 2: High Energy Hard Magnetic Materials
These include: - Alnico (Al–Ni–Co alloys), - Ferrites (ceramic magnets), - Rare-earth magnets (e.g., NdFeB, SmCo). Such materials are called hard magnetic materials and are used in: - Motors and generators, - Magnetic sensors, - Audio devices and permanent magnet-based assemblies. Step 3: Elimination of Incorrect Options
- Ti–Al–V: Typically used in aerospace alloys, not magnetic.
- Commercial iron: Soft magnetic, easily magnetized and demagnetized.
- Cu–Zn (brass): Non-magnetic. Conclusion: Permanent magnets are made from high energy hard magnetic materials.