Grade 10
  1. Mechanics  1.1. Dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. Displacement and Distance  1.1.4. Speed and Velocity  1.1.5. Acceleration  1.1.6. Graphical representation of motion  1.1.7. Equations of motion  1.1.8. Free fall and acceleration due to gravity  1.1.9. Projectile motion  1.1.10. Relative speed  1.2. Dynamics  1.2.1. Newton's Laws of Motion  1.2.2. Inertia and mass  1.2.3. Force and its types  1.2.4. action and reaction force  1.2.5. Friction and its effects  1.2.6. Coefficient of friction  1.2.7. Circular motion  1.2.8. Centripetal force and centripetal acceleration  1.2.9. Momentum and Impulse  1.2.10. Conservation of momentum  1.2.11. Newton's third law and applications  1.3. Work, Energy and Power  1.3.1. Work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy  1.3.5. Mechanical energy  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.3.8. Renewable and non-renewable energy sources  1.4. Gravitational force  1.4.1. Newton's law of universal gravitation  1.4.2. Gravitational field and field strength  1.4.3. Acceleration due to gravity on different planets  1.4.4. Kepler's laws of planetary motion  1.4.5. Orbits and satellites  1.4.6. Weight and apparent weight  1.4.7. Gravitational potential energy
  2. Properties of matter  2.1. States of matter  2.1.1. Solid, liquid and gas  2.1.2. Molecular structure of matter  2.1.3. Intermolecular forces  2.1.4. Plasma and Bose–Einstein condensate  2.2. Pressure  2.2.1. Definition of Pressure  2.2.2. Pressure in liquids  2.2.3. Atmospheric pressure  2.2.4. Pascal's principle  2.2.5. Archimedes' Principle and Buoyancy  2.2.6. Surface tension and capillarity  2.3. Elasticity  2.3.1. Hooke's law  2.3.2. Stress and strain  2.3.3. Elastic Limit and Modulus of Elasticity  2.3.4. Applications of Elasticity
  3. Thermal physics  3.1. heat and temperature  3.1.1. Difference Between Heat and Temperature  3.1.2. Temperature scale  3.1.3. Thermal expansion  3.1.4. Thermal equilibrium  3.2. Heat transfer  3.2.1. Conductivity  3.2.2. Convection  3.2.3. Radiation  3.2.4. Insulation and its applications  3.3. Thermal properties of matter  3.3.1. Specific heat capacity  3.3.2. Latent heat and phase change  3.3.3. Boiling and Melting Point  3.3.4. Heat engines and refrigeration  3.4. Laws of Thermodynamics  3.4.1. Zeroth law of thermodynamics  3.4.2. First law of thermodynamics  3.4.3. Second law of thermodynamics  3.4.4. Carnot cycle
  4. Waves and optics  4.1. Nature and properties of waves  4.1.1. Types of waves in nature and properties of waves  4.1.2. Transverse and longitudinal waves  4.1.3. Wave parameters  4.1.4. Reflection and refraction of waves  4.1.5. Superposition and Interference  4.1.6. Standing Waves and Resonance  4.1.7. Doppler effect  4.2. Sound waves  4.2.1. Characteristics of sound waves  4.2.2. Speed of sound in different mediums  4.2.3. Applications of sound waves  4.2.4. Ultrasound and its uses  4.3. Light Waves and Optics  4.3.1. Nature of light  4.3.2. Reflection of light  4.3.3. Laws of reflection  4.3.4. Mirrors and Image Formation  4.3.5. Refraction of light  4.3.6. Snell's Law  4.3.7. Lenses and Image Formation  4.3.8. Total internal reflection and critical angle  4.3.9. Optical fibre  4.4. Optical Instruments  4.4.1. Microscope  4.4.2. Telescope  4.4.3. Human eye and vision defects  4.4.4. Camera and its working principle
  5. Electricity and Magnetism  5.1. Electrostatics  5.1.1. Electric charge and its properties  5.1.2. Conductors and Insulators  5.1.3. Coulomb's law  5.1.4. Electric field and field lines  5.1.5. Electric potential and potential difference  5.1.6. Capacitors and Capacitance  5.2. Current Electricity  5.2.1. Electric current and its measurement  5.2.2. Ohm's law  5.2.3. Resistance and resistivity  5.2.4. Series and Parallel Circuits  5.2.5. Electric power and energy  5.2.6. Kirchhoff's Laws  5.3. Magnetism and Electromagnetism  5.3.1. Magnetic field and field lines  5.3.2. Magnetic effects of electric current  5.3.3. Electromagnetic induction  5.3.4. Faraday's laws of electromagnetic induction  5.3.5. Transformers and Applications  5.3.6. AC and DC current
  6. Modern Physics  6.1. Nuclear physics  6.1.1. Structure of the atom  6.1.2. Bohr's atomic model  6.1.3. Electron Energy Levels  6.1.4. X-rays and applications  6.2. Radioactivity  6.2.1. Types of radiation  6.2.2. Half-life and radioactive decay  6.2.3. Nuclear reactions and applications  6.2.4. Fission and Fusion  6.3. Quantum physics  6.3.1. Wave–particle duality  6.3.2. Photoelectric effect  6.3.3. Energy quantization  6.3.4. Heisenberg's uncertainty principle
  7. Electronics and Communication  7.1. Semiconductors  7.1.1. Conductors, Insulators and Semiconductors  7.1.2. Diodes and their applications  7.1.3. Transistors and Logic Gates  7.1.4. LEDs and photodiodes  7.2. Communication Systems  7.2.1. Basics of communication  7.2.2. Analog and digital signals  7.2.3. Wireless and optical fibre communication  7.2.4. Radio Waves and Modulation

Grade 10 → Electricity and Magnetism → Magnetism and Electromagnetism ↓


Faraday's laws of electromagnetic induction


Faraday's laws of electromagnetic induction are the fundamental principles behind how electric currents are generated in magnetic fields. These laws are named after Michael Faraday, a pioneering scientist who performed many experiments on magnetism and electricity in the 19th century. Faraday's discoveries form the cornerstone of how electromagnetic phenomena are understood and used in technology today.

Introduction to electromagnetic induction

Electromagnetic induction describes the process by which an electric current is generated in a conductor in a changing magnetic field. It is a key principle behind many of our electrical devices, including generators, transformers, and inductors. Understanding electromagnetic induction helps explain how electricity is generated and transferred.

Faraday's first law of electromagnetic induction

Faraday's first law states that an electromotive force (EMF) is induced in a conductor when the magnetic flux linked with it changes. In simple terms, when you move a magnet through a coil of wire or vice versa, you can generate an electric current.

Example: Moving a magnet through a coil

Imagine a simple coil of wire connected to a galvanometer, an instrument used to detect current. When a bar magnet is moved towards or away from the coil, the galvanometer needle moves. This indicates that an electric current is induced in the coil.

coil connected to galvanometer

Entry of magnet into the coil ➔ induced current ➔ movement of galvanometer needle
Magnet Coil

This motion produces a change in the magnetic flux through the coil, which induces an electromotive force and produces an electric current. As you can see in the diagram above, the interaction between the coil and the magnetic field leads to induction.

Faraday's second law of electromagnetic induction

Faraday's second law quantifies the induced electromotive force. It states that the magnitude of the induced electromotive force is proportional to the rate of change of the magnetic flux linked with the circuit.

Mathematically, Faraday's second law can be expressed as:

emf = -dΦ/dt

Here, EMF represents the electromotive force in volts, and Φ is the magnetic flux measured in webers (Wb). The negative sign in Faraday's equation indicates the direction of the induced EMF and current, which is consistent with Lenz's law.

Example: Fast vs. slow speed of a magnet

If you move the magnet faster through the coil, the rate of change of magnetic flux increases, making the EMF higher and thus producing a higher current. Conversely, moving the magnet slowly results in a smaller change in magnetic flux and a correspondingly lower EMF.

High speed ➔ High rate of change ➔ High emf ➔ High current
Slow speed ➔ Low rate of change ➔ Low emf ➔ Low current

Lenz's law

Lenz's law further defines the direction of the induced current. It states that the direction of the induced current is such that it opposes the change in the magnetic flux that produces it.

Lenz's law is indicated by the negative sign in Faraday's formula. The induced current creates its own magnetic field, which tries to keep the original magnetic field within the coil constant.

Examples: Antiwar movement

Suppose a bar magnet is being pushed into a coil. The direction of the induced current is such that it creates a magnetic field that repels the motion of the magnet. Pull the magnet, and the induced magnetic field attracts the magnet back. This is nature's way of obeying the law of conservation of energy.

Applications of electromagnetic induction

Faraday's laws play an important role in modern technology. Let's take a look at some of the major applications:

Electric generator

Electric generators convert mechanical energy into electrical energy using the principle of electromagnetic induction. When a conductor (coil) is rotated in a magnetic field, an EMF is induced, which drives a current. This is the basic operating principle behind power stations that provide electricity to millions of homes.

Transformers

Transformers use electromagnetic induction to increase or decrease AC voltage in electrical circuits. They consist of two coils of wire placed next to each other. The changing current in the primary coil induces a current in the secondary coil through mutual induction. This is essential for power distribution over long distances.

Primary coil Secondary coil

Induction cooktops

Induction cooktops use electromagnetic induction to directly heat pots and pans. An alternating current flows through a coil beneath the cooktop's surface. This generates a changing magnetic field, which induces an electric current within the metal pot, resulting in heat.

Inductive charging

Inductive charging is a wireless way to charge electronic devices, such as smartphones. It involves creating a magnetic field in the charging station that induces a current in the device, charging the battery without the need for direct electrical contact.

Conclusion

Faraday's laws of electromagnetic induction are foundational to understanding how electricity is created and used. Insights gained from these laws enable electrical energy to be harnessed, shaping the technological landscape we live in.

From the simple experiment of moving a magnet near a coil to large-scale generation of electricity, Faraday's contributions continue to have a profound influence on modern technology and scientific understanding. As we explore these concepts further, it is important to appreciate the simplicity and power of Faraday's insights into electromagnetic phenomena.


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Faraday's laws of electromagnetic induction

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