Sifat dan Kinerja Material P4

What is the primary origin of magnetism in materials?

• Thermal vibration

• Electron spin and orbital motion

• Crystal defects

• Atomic mass

Which type of magnetic material opposes an external magnetic field?

• Ferromagnetic

• Paramagnetic

• Diamagnetic

• Ferrimagnetic

What is the formula for a typical ferrite structure?

• M²⁺O²⁻ - (Fe³⁺)₂(O²⁻)₃

• Fe²⁺O²⁻ - (Mn³⁺)₂(O²⁻)₃

• Al²⁺O²⁻ - (Ni³⁺)₂(O²⁻)₃

• Co²⁺O²⁻ - (Zn³⁺)₂(O²⁻)₃

Which temperature represents the point where ferromagnets become paramagnetic?

• Melting point

• Néel temperature

• Curie temperature

• Saturation point

What is the effect of structural defects on coercivity?

• Increase coercivity

• Decrease coercivity

• No effect

• Enhances permeability

In the hysteresis loop, what does the area represent?

• Electrical resistance

• Magnetic flux

• Energy loss per cycle

• Temperature variation

What is the main advantage of Nd₂Fe₁₄B magnets over SmCo₅?

• Higher cost

• Easier to demagnetize

• Comparable energy products at lower cost

• Non-magnetic behavior

What is the direction called where magnetization is achieved with the least applied field?

• Hard axis

• Easy axis

• Neutral axis

• Perpendicular axis

Why are iron-silicon alloys commonly used in transformer cores?

• They have low electrical resistivity

• They are easy to demagnetize

• They have high electrical resistivity and are easily magnetized

• They are non-magnetic

How do magnetic domains behave under an applied external field?

• They disappear completely

• They randomly orient

• Favorable domains grow, unfavorable ones shrink

• They form a liquid-like state