Magnetism And Matter (VSAQs)

Physics-2 | 8. Magnetism and Matter – VSAQs:
Welcome to VSAQs in Chapter 8: Magnetism and Matter. This page features the key FAQs for Very Short Answer Questions. Each answer is provided in simple English and follows the exam format. This will assist in focusing on important details and securing top marks in your final exams.

VSAQ-1 : What is the magnetic moment associated with a solenoid?

The magnetic moment (μ) associated with a solenoid is determined by the formula:

$$\mu = n \cdot I \cdot A$$

Where

  1. μ is the magnetic moment.
  2. n represents the number of turns per unit length of the solenoid.
  3. I is the current passing through the solenoid.
  4. A stands for the cross-sectional area of the solenoid.

This formula calculates the magnetic moment per unit length of the solenoid. To find the total magnetic moment, you would multiply this value by the length (L) of the solenoid:

Total Magnetic Moment = μ ⋅ L

VSAQ-2 : What are the S.I units of magnetic moment, magnetic induction and magnetic field?

The SI units for:

  1. Magnetic Moment (M) is Ampere-square meter (A·m²).
  2. Magnetic Induction (B) is Tesla (T) or Newton per Ampere-meter (N/A·m).
  3. Magnetic Field (H) is also Tesla (T).

VSAQ-3 : Magnetic lines form continuous closed loops. Why?

Magnetic lines of force form continuous closed loops because they originate from the north pole, curve around the magnet, and enter the south pole. Inside the magnet, these lines of force travel from the south pole to the north pole, thus completing the closed loop. This behavior is a fundamental property of magnetic fields and is a result of the conservation of magnetic flux in a closed system.

VSAQ-4 : Define magnetic declination.

Magnetic declination is the angle between magnetic north and true north at a specific location on the Earth’s surface. When using a compass, it aligns with the horizontal component of the Earth’s magnetic field, indicating the magnetic north direction. However, this magnetic north direction does not always align perfectly with the geographic north direction, known as true north, which points to the North Pole. The difference in these two directions is known as the magnetic declination and can vary depending on the location on the Earth’s surface.

VSAQ-5 : Define magnetic inclination or angle of dip.

Magnetic inclination, also known as the angle of dip, is the angle formed between the Earth’s magnetic field lines and the horizontal plane at a specific location on the Earth’s surface. A positive inclination indicates a downward magnetic field direction, while a negative inclination signifies an upward magnetic field direction. This angle varies across different locations on the Earth’s surface.

VSAQ-6 : Classify the following materials with regard to magnetism : Manganese, Cobalt, Nickel, Bismuth, Oxygen, Copper.

The classification of materials with regard to magnetism:

  1. Manganese, Cobalt, and Nickel are ferromagnetic and exhibit strong magnetic properties.
  2. Bismuth and Copper are diamagnetic and display weak magnetic repulsion.
  3. Oxygen is paramagnetic and is slightly attracted to magnets when in a magnetic field.

VSAQ-7 : What happens to compass needles at the Earth’s poles?

At Earth’s poles, a compass needle becomes nearly horizontal and does not point towards the magnetic north. Instead, it exhibits the following behaviors:

  1. At the magnetic North Pole, the compass needle points straight down towards the Earth’s center.
  2. At the magnetic South Pole, the compass needle points straight up, away from the Earth’s surface.

The angle between the compass needle and the horizontal surface reaches 90 degrees at the poles, representing the maximum angle of dip. This is because the magnetic field lines converge at the poles, leading to these unique compass needle orientations.

VSAQ-8 : What do you understand by the ‘magnetization’ of a sample?

Magnetization of a sample involves aligning the magnetic moments of the atoms or molecules within the sample in a specific direction when exposed to an external magnetic field. It quantifies the magnetic moment per unit volume of the sample, typically denoted as ‘M’. The ability to induce magnetization in a material can be temporary, as seen in soft magnetic materials, or permanent, as in hard magnetic materials, depending on the properties of the material. This process is fundamental in understanding and utilizing the magnetic properties of materials in various applications.

VSAQ-9 : Define Magnetisation of a sample. What is its SI unit?

Magnetization of a sample is the measure of the density of induced magnetic dipole moments within a magnetic material when it is exposed to an external magnetic field. Mathematically, it is defined as:

$$\text{Magnetization (M)} = \frac{\text{Magnetic Moment (m)}}{\text{Volume (V)}}$$

The SI unit of magnetization is amperes per meter (A/m), or in the CGS (centimeter-gram-second) system, it can be expressed in tesla (T).

VSAQ-10 : Define Magnetic susceptibility. Mention its unit.

Magnetic susceptibility is a measure of how easily a material can be magnetized when exposed to an external magnetic field. It is defined as the ratio of the intensity of magnetization (M) to the magnetizing field (H) applied to the material.

Mathematically, magnetic susceptibility (χ) is given by:

$$\chi = \frac{M}{H}​$$

The unit of magnetic susceptibility is dimensionless, as it represents the ratio of two physical quantities with the same units, such as amperes per meter (A/m). In the CGS (centimeter-gram-second) system, it is expressed as emu/cm³ per oersted (emu/cm³/Oe).