Chapter-5 Magnetism and Matter — Online MCQ Test
PHYSICS · Grade 12 · CBSE(NCERT)
Practice Chapter-5 Magnetism and Matter with a free chapter-wise online MCQ test.
This chapter covers: bar magnet - magnetic field lines - Earth's magnetism - paramagnetic - diamagnetic - ferromagnetic materials.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter-5 Magnetism and Matter — Important Questions & Answers
What is the SI unit of magnetic dipole moment?
- A. A·m²
- B. T·m
- C. Wb/m
- D. H/m
Answer: A. A·m²
The magnetic dipole moment is measured in Ampere-meter squared (A·m²), which represents the product of current and area.
The magnetic dipole moment is measured in Ampere-meter squared (A·m²), which represents the product of current and area.
Which of the following materials is diamagnetic?
- A. Iron
- B. Cobalt
- C. Copper
- D. Nickel
Answer: C. Copper
Copper is diamagnetic as it has no unpaired electrons and opposes external magnetic fields; iron, cobalt, and nickel are ferromagnetic.
Copper is diamagnetic as it has no unpaired electrons and opposes external magnetic fields; iron, cobalt, and nickel are ferromagnetic.
The magnetic field lines of a bar magnet never cross each other. Why?
- A. Because they are parallel to each other
- B. Because the direction of the field is unique at every point
- C. Because the magnet is too weak
- D. Because they are confined within the magnet
Answer: B. Because the direction of the field is unique at every point
At any point in space, the magnetic field has only one unique direction, so field lines cannot cross as each point can have only one tangent direction.
At any point in space, the magnetic field has only one unique direction, so field lines cannot cross as each point can have only one tangent direction.
What is the angle of dip at the magnetic equator?
- A. 0°
- B. 45°
- C. 90°
- D. 180°
Answer: A. 0°
At the magnetic equator, the Earth's magnetic field is horizontal, so the angle of dip is 0°. The angle of dip increases as we move toward the magnetic poles.
At the magnetic equator, the Earth's magnetic field is horizontal, so the angle of dip is 0°. The angle of dip increases as we move toward the magnetic poles.
A paramagnetic material has magnetic susceptibility (χ):
- A. χ > 1 (positive and large)
- B. χ ≈ 10⁻⁵ to 10⁻³ (small and positive)
- C. χ ≈ -10⁻⁶ to -10⁻⁵ (small and negative)
- D. χ = 0
Answer: B. χ ≈ 10⁻⁵ to 10⁻³ (small and positive)
Paramagnetic materials have small positive magnetic susceptibility (χ ≈ 10⁻⁵ to 10⁻³), indicating weak attraction to magnetic fields.
Paramagnetic materials have small positive magnetic susceptibility (χ ≈ 10⁻⁵ to 10⁻³), indicating weak attraction to magnetic fields.
When a bar magnet is cut into two equal halves along its length, what happens?
- A. Two separate monopoles are created
- B. Each half loses its magnetic properties
- C. Each half becomes a complete bar magnet with its own N and S poles
- D. Only one half retains magnetic properties
Answer: C. Each half becomes a complete bar magnet with its own N and S poles
Cutting a bar magnet produces two new complete magnets, each with both north and south poles. Magnetic monopoles do not exist.
Cutting a bar magnet produces two new complete magnets, each with both north and south poles. Magnetic monopoles do not exist.
Compare the magnetic susceptibility values: If χ₁ is for aluminum (paramagnetic), χ₂ for bismuth (diamagnetic), and χ₃ for iron (ferromagnetic), then the correct order is:
- A. χ₂ > χ₁ > χ₃
- B. χ₃ > χ₁ > χ₂
- C. χ₁ > χ₃ > χ₂
- D. χ₂ > χ₃ > χ₁
Answer: B. χ₃ > χ₁ > χ₂
Iron (ferromagnetic, χ₃ >> 1) > Aluminum (paramagnetic, χ₁ ≈ 10⁻⁵) > Bismuth (diamagnetic, χ₂ ≈ -10⁻⁵). Ferromagnetic > Paramagnetic > Diamagnetic.
Iron (ferromagnetic, χ₃ >> 1) > Aluminum (paramagnetic, χ₁ ≈ 10⁻⁵) > Bismuth (diamagnetic, χ₂ ≈ -10⁻⁵). Ferromagnetic > Paramagnetic > Diamagnetic.
The magnetic field on the equatorial axis of a bar magnet at distance r from its center is B. What is the field at the same distance on the axial line?
- A. B
- B. 2B
- C. B/2
- D. 4B
Answer: B. 2B
At equal distances, the axial field is twice the equatorial field: B_axial = 2μ₀m/4πr³ and B_equatorial = μ₀m/4πr³, so B_axial = 2B_equatorial.
At equal distances, the axial field is twice the equatorial field: B_axial = 2μ₀m/4πr³ and B_equatorial = μ₀m/4πr³, so B_axial = 2B_equatorial.
The relationship between magnetic field B, permeability μ, and magnetization M in a material is B = μ₀(H + M). When a ferromagnetic material is magnetized near saturation, M becomes:
- A. Very large compared to H, making B ≈ μ₀M
- B. Zero, making B = μ₀H
- C. Negative
- D. Equal to H
Answer: A. Very large compared to H, making B ≈ μ₀M
Near saturation of a ferromagnetic material, magnetization M becomes very large (as all domains align), so M >> H and B ≈ μ₀M dominates the expression.
Near saturation of a ferromagnetic material, magnetization M becomes very large (as all domains align), so M >> H and B ≈ μ₀M dominates the expression.
A bar magnet is suspended freely in Earth's magnetic field. If the magnet is slightly rotated from its equilibrium position and released, it will oscillate. The period of oscillation depends on:
- A. Only the magnetic moment of the magnet
- B. Only Earth's magnetic field strength
- C. The moment of inertia, magnetic moment, and Earth's field strength
- D. Only the length of the magnet
Answer: C. The moment of inertia, magnetic moment, and Earth's field strength
The restoring torque τ = mB sin θ gives equation of motion; for small angles, T = 2π√(I/mB), where I is moment of inertia, m is magnetic moment, and B is Earth's field.
The restoring torque τ = mB sin θ gives equation of motion; for small angles, T = 2π√(I/mB), where I is moment of inertia, m is magnetic moment, and B is Earth's field.