# Chapter 9 – Magnetic Field and Field Lines

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:

Introduction

Have you ever been fascinated by how bits of iron can stick to really old magnets? The closer you take a magnet to any iron object, the pull you feel gets stronger. This ‘pull’ you feel is the magnetic field. You will learn about magnets, magnetic fields and magnetic field lines in the paragraphs below.

What is a magnetic field?

A magnetic field is an invisible space around a magnet. It is used to describe the distribution of the magnetic force of a magnet. All magnets have a definite region around it in which the forces of attraction and repulsion can be detected. This space is known as the magnetic field.

What are magnetic field lines?

Magnetic field lines are the imaginary lines drawn around a magnet to show its magnetic field distribution. The magnitude of a magnetic field can be determined by the density of these imaginary magnetic field lines. This magnetic field is comparatively much stronger near the poles of the magnet. And, it gets weaker as we move away from the poles.

#### How to find the magnetic field lines around a bar magnet?

We will clarify the concept of a magnetic field by performing a simple experiment. Firstly, fix a sheet of white paper on a table and then mark its center. Next, fix a bar magnet at the center mark. Then carefully sprinkle some iron filings around the bar magnet. Gently tap on the table. You will observe that the iron filings are making a symmetrical pattern that is dense near the north and south poles of the magnet. You will also notice that these lines are more or less continuous and the fact that it gets less dense near the sides of the magnet. These lines that are formed represent the magnetic field lines of the bar magnet and the extent of its magnetic field.

A few properties of magnetic field lines

• Magnetic field lines are imaginary lines around a magnet that represents the magnetic field of the magnet.
• A magnetic field line is always a closed and continuous curve.
• A magnetic field line is always directed from the north pole to the south pole outside the magnet and from the south pole to the magnet’s north pole.
• The magnetic field lines are densest near the magnet’s poles, where the magnetic field is stronger. The magnetic field lines are far apart near the magnet’s middle, where the magnetic field is weak.
• The magnetic field lines do not intersect each other because if they do so, these will point to two different directions of the magnetic field at one point, which is not scientifically possible.

#### How is a magnetic field produced?

A magnetic field around a magnet can be produced by a magnet, a moving charge, or by electric currents. The magnetic field is mathematically represented by the symbol ‘B’. Its unit is Tesla.

We know that all matter is made up of tiny microscopic particles called atoms. The nucleus of an atom consists of positively charged particles called protons and neutral subatomic particles called neutrons. The negatively charged particles, also called electrons, revolve around this nucleus in circular orbits. This uniform directional movement creates a magnetic field. The direction of orbit and spin decides the direction of the magnetic field. This property is more evident in matter than can be magnetised, such as iron, and less in matter such as plastic or other non-metals.

#### Earth’s magnetic field

Suppose a piece of magnet is suspended freely from a thread and is allowed to rotate in a horizontal plane. In that case, it will automatically align itself in the geographical north-south direction and then gradually come to rest. The real magnetic north and south poles are, however, different from the geographical north and south poles. The Earth’s uniform magnetic field determines these geographical poles. This magnetic field generated by the Earth’s magnetic properties is uniform in nature and extends upto five times the Earth’s radius itself.

#### FAQs

1. What are magnetic fields and field lines?

A magnetic field is a region around a magnet where the magnet’s magnetic properties can be felt and realized. Magnetic field lines are the imaginary lines drawn to explain the magnetic field’s distribution around a magnet.

2. What is the difference between the magnetic field and magnetic field lines?

The magnetic field is the space around a magnet where the magnet’s magnetic properties in question can be felt. It is a real phenomenon. However, magnetic field lines are imaginary and represent the magnetic field around a magnet.

3. How are magnetic field lines drawn?

Magnetic field lines are always drawn from the north to the south poles outside the magnet and from the south pole to the magnet’s north pole.

4. What is the formula for a magnetic field?

The dimensional formula for a magnetic field is given by [M^1 T^-2 I^-1]. Where, M= Mass, I= Current, L= Length, T= Time. The SI unit is Tesla(B).

5. Which is the stronger- magnetic field or electric field?

An Electric field is a stronger force than a magnetic field in clinical conditions if there are no interfering forces.

MSVgo is an educational application with a wide range of video libraries, explanatory notes, animations, and interactive practice questions. Its expansive focus on the core understanding of any subject matter and conceptual learning modules makes it a state of the art application. Children can learn and have fun while browsing a vast video library through it. MSVgo is one of the best applications available on both Android and iOS devices for free. For more information on formulae and reactions, download the MSVgo application today!

### High School Physics

• Alternating Current
• Atoms
• Communication Systems
• Current Electricity
• Dual nature of Radiation and Matter
• Electric Charges and Fields
• Electricity
• Electromagnetic Induction
• Electromagnetic Waves
• Electrons and Photons
• Electrostatic Potential and Capacitance
• Fluid Pressure
• Force and Acceleration
• Force And Laws Of Motion
• Gravitation
• Internal Energy
• Kinetic Theory
• Law of motion
• Light – Reflection And Refraction
• Magnetic Effects Of Electric Current
• Magnetism and Matter
• Management Of Natural Resources
• Mechanical properties of Fluids
• Mechanical properties of Solids
• Motion
• Motion in a plane
• Motion in a straight line
• Moving Charges and Magnetism
• Nuclear Energy
• Nuclei
• Oscillations
• Our Environment
• Paths of Heat
• Physical world
• Ray optics and optical instruments
• Semiconductor Devices
• Semiconductor Electronics: Materials, Devices and Simple Circuits
• Simple Machines
• Sound
• Sources Of Energy
• Specific and Latent Heats
• Spherical Mirrors
• Static Electricity
• Systems of Particles and Rotational motion
• Thermal properties of matter
• Thermodynamics
• Units and Measurement
• Vectors, Scalar Quantities and Elementary Calculus
• Wave Optics
• Waves
• Work, Power and Energy

### High School Chemistry

• Acids, Bases and Salts
• Alcohols, Phenols and Ethers
• Aldehydes, Ketones and Carboxylic Acids
• Aliphatic and Aromatic Hydrocarbons
• Alkyl and Aryl Halides
• Amines
• Analytical Chemistry
• Atomic Structure
• Atoms And Molecules
• Basic concepts of Chemistry
• Biomolecules
• Carbon And Its Compounds
• Carboxylic acids and Acid Derivatives
• Chemical Bonding and Molecular Structures
• Chemical Energetics
• Chemical Equilibria
• Chemical Kinetics
• Chemical Reactions And Equations
• Chemical Reactions and Their Mechanisms
• Chemistry in Everyday Life
• Chemistry of p-Block elements
• Chemistry of Transition and Inner Transition
• Classification of Elements
• Coordination Compounds
• Cyanide, Isocyanide, Nitro compounds and Amines
• Electrochemistry
• Electrolysis
• Elements, Compounds and Mixtures
• Environmental Chemistry
• Equilibrium
• Ethers and Carbonyl compounds
• Haloalkanes and Haloarenes
• Hydrocarbons
• Hydrogen
• Ideal solutions
• Introduction to Organic Chemistry
• Ionic equilibria
• Matter
• Matter Around Us
• Matter In Our Surroundings
• Metallurgy
• Metals And Non-Metals
• Mole Concept and Stoichiometry
• Natural Resources
• Organic Chemistry – Basic Principles
• Periodic Classification of Elements
• Physical and Chemical Changes
• Physical and Chemical Properties of Water
• Polymers
• Preparation, Properties and Uses of Compounds
• Principles and Processes of Isolation of Elements
• Redox Reactions
• Relative Molecular Mass and Mole
• States of Matter
• Structure Of The Atom
• Study of Compounds
• Study of Gas Laws
• Study of Representative Elements
• Surface Chemistry
• The d-block and f-block elements
• The Gaseous State
• The p-Block Elements
• The Periodic Table
• The s-Block Elements
• The Solid State
• Thermodynamics

### High School Biology

• Absorption and Movement of Water in Plants
• Anatomy of Flowering Plants
• Animal Kingdom
• Bacteria and Fungi-Friends and Foe
• Biodiversity and Conservation
• Biofertilizers
• Biological Classification
• Biomedical Engineering
• Biomolecules
• Biotechnology and its Applications
• Biotic Community
• Body Fluids and Circulation
• Breathing and Exchange of Gases
• Cell – Unit of Life
• Cell Cycle and Cell Division
• Cell Division and Structure of Chromosomes
• Cell Reproduction
• Cellular Respiration
• Chemical Coordination and Integration
• Circulation
• Control And Coordination
• Crop Improvement
• Digestion and Absorption
• Diversity In Living Organisms
• Ecosystem
• Environmental Issues
• Excretory Products and their Elimination
• Flowering Plants
• Genes and Chromosomes
• Health and Diseases
• Health and Its Significance
• Heredity And Evolution
• Heredity and Variation
• How Do Organisms Reproduce?
• Human Diseases
• Human Eye And Colourful World
• Human Health and Disease
• Human Population
• Human Reproduction
• Hygiene
• Improvement In Food Resources
• Integumentary System- Skin
• Kingdom Fungi
• Kingdom Monera
• Kingdom Protista
• Life Processes
• Locomotion and Movement
• Microbes in Human Welfare
• Mineral Nutrition
• Molecular Basis of Inheritance
• Morphology of Flowering Plants
• Neural Control And Coordination
• Nutrition in Human Beings
• Organism and Population
• Photosynthesis
• Photosynthesis in Higher Plants
• Plant Growth and Development
• Plant Kingdom
• Pollination and Fertilization
• Pollution; Sources and its effects
• Principles of Inheritance and Variation
• Reproduction and Development in Angiosperms
• Reproduction in Organisms
• Reproductive Health
• Respiration in Human Beings
• Respiration in Plants
• Respiratory System
• Sexual Reproduction in Flowering Plants
• Strategies for Enhancement in Food Production
• Structural Organisation in Animals
• Structural Organisation of the Cell
• The Endocrine System
• The Fundamental Unit Of Life
• The Living World
• The Nervous System and Sense Organs
• Tissues
• Transpiration
• Transport in Plants

### High School Math

• Algebra – Arithmatic Progressions
• Algebra – Complex Numbers and Quadratic Equations
• Algebra – Linear Inequalities
• Algebra – Pair of Linear Equations in Two Variables
• Algebra – Polynomials
• Algebra – Principle of Mathematical Induction
• Binomial Theorem
• Calculus – Applications of Derivatives
• Calculus – Applications of the Integrals
• Calculus – Continuity and Differentiability
• Calculus – Differential Equations
• Calculus – Integrals
• Geometry – Area
• Geometry – Circles
• Geometry – Conic Sections
• Geometry – Constructions
• Geometry – Introduction to Euclid’s Geometry
• Geometry – Three-dimensional Geometry
• Geometry – Lines and Angles
• Geometry – Straight Lines
• Geometry – Triangles
• Linear Programming
• Matrices and Determinants
• Mensuration – Areas
• Mensuration – Surface Areas and Volumes
• Number Systems
• Number Systems – Real Numbers
• Permutations and Combinations
• Probability
• Sequence and Series
• Sets and Functions
• Statistics
• Trignometry – Height and Distance
• Trignometry – Identities
• Trignometry – Introduction

### Middle School Science

• Acids, Bases And Salts
• Air and Its Constituents
• Basic Biology
• Body Movements
• Carbon and Its Compounds
• Cell – Structure And Functions
• Changes Around Us
• Chemical Effects Of Electric Current
• Coal And Petroleum
• Combustion And Flame
• Components Of Food
• Conservation Of Plants And Animals
• Crop Production And Management
• Electric Current And Its Effects
• Electricity And Circuits
• Elements and Compounds
• Fibre To Fabric
• Food production and management
• Force And Pressure
• Forests: Our Lifeline
• Friction
• Fun With Magnets
• Garbage In, Garbage Out
• Getting To Know Plants
• Health and Hygiene
• Heat
• Hydrogen
• Life Processes: Nutrition in Animals and Plants
• Materials: Metals And Non-Metals
• Matter and Its States
• Metals and Non-metals
• Micro Organisms: Friend And Foe
• Motion And Measurement Of Distances
• Motion And Time
• Nutrition In Animals
• Nutrition In Plants
• Organization in Living Things
• Our Environment
• Physical And Chemical Changes
• Pollution and conservation
• Pollution Of Air And Water
• Reaching The Age Of Adolescence
• Reproduction In Animals
• Reproduction In Plants
• Respiration In Organisms
• Rocks and Minerals
• Separation Of Substances
• Simple Machines
• Soil
• Some Natural Phenomena
• Sorting Materials Into Groups
• Sound
• Stars And The Solar System
• Structure of Atom
• Synthetic Fibers And Plastics
• The Living Organisms And Their Surroundings
• Transfer of Heat
• Transformation of Substances
• Transportation In Animals And Plants
• Universe
• Waste-water Story
• Water: A Precious Resource
• Weather, Climate And Adaptations Of Animals To Climate
• Winds, Storms And Cyclones

### Middle School Math

• Area and Its Boundary
• Boxes and Sketches
• Data Handling
• Fun With Numbers
• Heavy and Light
• How Many
• Long And Short
• Mapping
• Measurement
• Money
• Multiplication and Factors
• Multiply and Divide
• Numbers
• Parts and Wholes
• Pattern Recognition
• Patterns
• Play With Patterns
• Rupees And Paise
• Shapes And Angles
• Shapes And Designs
• Shapes and Space
• Similarity
• Smart Charts
• Squares
• Subtraction
• Tables And Shares
• Tenths and Hundredths
• Time