Topics
Electric Charges and Fields
- Electric Charge
- Conductors and Insulators
- Basic Properties of Electric Charge
- Coulomb’s Law
- Forces between Multiple Charges
- Electric Field
- Electric Field Due to a System of Charges
- Physical Significance of Electric Field
- Electric Field Lines
- Electric Flux
- Electric Dipole
- Dipole in a Uniform External Field
- Continuous Charge Distribution
- Gauss’s Law
- Application of Gauss' Law
Electrostatics
Current Electricity
Electrostatic Potential and Capacitance
- Electric Potential and Potential Energy
- Electrostatic Potential
- Electric Potential Due to a Point Charge
- Potential Due to an Electric Dipole
- Potential due to a System of Charges
- Equipotential Surfaces
- Relation Between Electric Field and Electrostatic Potential
- Potential Energy of a System of Charges
- Potential Energy of a Single Charge
- Potential Energy of a System of Two Charges in an External Field
- Potential Energy of a Dipole in an External Field
- Electrostatics of Conductors
- Dielectrics and Polarisation
- Capacitors and Capacitance
- The Parallel Plate Capacitor
- Effect of Dielectric on Capacitance
- Combination of Capacitors
- Energy Stored in a Charged Capacitor
Magnetic Effects of Current and Magnetism
Current Electricity
- Electric Current
- Electric Currents in Conductors
- Ohm's Law
- Drift of Electrons and the Origin of Resistivity
- Mobility of Electrons
- Limitations of Ohm’s Law
- Resistivity of Various Materials
- Temperature Dependence of Resistivity
- Electrical Energy and Power in Conductors
- Cells, EMF, and Internal Resistance
- Cells in Series and in Parallel
- Kirchhoff’s Laws
- Wheatstone Bridge
Electromagnetic Induction and Alternating Currents
Moving Charges and Magnetism
- Electromagnetism
- Magnetic force
- Motion in a Magnetic Field
- Magnetic Field Due to a Current-carrying Conductor: Biot-savart's Law
- Applications of Biot-Savart's Law > Magnetic Field at the Axis of a Circular Current-carrying Loop
- Ampere’s Circuital Law
- Solenoid
- Force Between Two Parallel Currents (Ampere’s Law)
- Torque on a Rectangular Current Loop in a Uniform Magnetic Field
- Circular Current Loop as a Magnetic Dipole
- Moving Coil Galvanometer
- Kirchhoff’s Laws
Electromagnetic Waves
Magnetism and Matter
Electromagnetic Induction
Optics
Dual Nature of Radiation and Matter
Alternating Current
Atoms and Nuclei
Electromagnetic Waves
Electronic Devices
Ray Optics and Optical Instruments
- Ray Optics Or Geometrical Optics
- Reflection of Light by Spherical Mirrors
- Sign Convention for Reflection by Spherical Mirrors
- Focal Length of Spherical Mirrors
- Mirror Equation of Spherical Mirrors
- Refraction of Light
- Total Internal Reflection
- Applications of Total Internal Reflection
- Refraction at a Spherical Surfaces
- Refraction by a Lens
- Power of a Lens
- Combined Focal Length of Two Thin Lenses in Contact
- Refraction of Light Through a Prism
- Optical Instruments
- Microscope and it’s types
- Telescope
Wave Optics
- Concept of Wave Optics
- Huygens Principle
- Refraction of a Plane Wave
- Refraction at a Rarer Medium
- Reflection of a Plane Wave by a Plane Surface
- Coherent and Incoherent Addition of Waves
- Interference of Light Waves and Young’s Experiment
- Diffraction of Light
- The Single Slit
- Seeing the Single Slit Diffraction Pattern
- Polarisation of Light
Communication Systems
The Special Theory of Relativity
Dual Nature of Radiation and Matter
- Understanding Dual Nature of Radiation and Matter
- Electron Emission
- Photoelectric Effect - Hertz’s Observations
- Photoelectric Effect - Hallwachs’ and Lenard’s Observations
- Experimental Study of Photoelectric Effect
- Effects of Intensity and Frequency on Photocurrent
- Photoelectric Effect and Wave Theory of Light
- Einstein’s Photoelectric Equation: Energy Quantum of Radiation
- Particle Nature of Light: The Photon
- Wave Nature of Matter
Atoms
Nuclei
Semiconductor Electronics - Materials, Devices and Simple Circuits
Communication Systems
- Detection of Amplitude Modulated Wave
- Production of Amplitude Modulated Wave
- Basic Terminology Used in Electronic Communication Systems
- Sinusoidal Waves
- Modulation and Its Necessity
- Amplitude Modulation (AM)
- Need for Modulation and Demodulation
- Satellite Communication
- Propagation of EM Waves
- Bandwidth of Transmission Medium
- Bandwidth of Signals
The Special Theory of Relativity
- The Special Theory of Relativity
- The Principle of Relativity
- Maxwell'S Laws
- Kinematical Consequences
- Dynamics at Large Velocity
- Energy and Momentum
- The Ultimate Speed
- Twin Paradox
Estimated time: 6 minutes
CBSE: Class 12
Introduction
The energy of the electron in a hydrogen atom has a definite value in each allowed orbit. The energy of the electron in the innermost orbit is the lowest. This state is called the ground state.
For hydrogen atom, the energy of the electron in the first orbit is:
E1 = −13.6 eV
This means that 13.6 eV of energy must be supplied to remove the electron completely from the atom in its ground state. This energy is called the ionisation energy of hydrogen.
CBSE: Class 12
Excited States
When a hydrogen atom absorbs energy, its electron can jump from the ground state to a higher orbit. Such a state is called an excited state.
If the electron jumps to the second orbit, the energy of the atom becomes:
E2 = −3.40 eV
Therefore, the energy required to raise the atom from the ground state to the first excited state is:
E2 − E1 = (−3.40) − (−13.6) = 10.2 eV
If the electron jumps to the third orbit, the energy of the atom is:
E3 = −1.51 eV
So, the energy required to raise the atom from the ground state to the second excited state is:
E3 − E1 = (−1.51) − (−13.6) = 12.09 eV
CBSE: Class 12
Energy States of the Hydrogen Atom
- The ground state corresponds to the lowest energy of the atom.
- The energy of the electron in a hydrogen atom is negative in bound states.
- As the orbit number increases, the energy becomes less negative.
- The energy required to remove an electron from an excited state is less than that required to remove an electron from the ground state.
- When the electron is completely free from the atom, its energy is taken as zero.
CBSE: Class 12
Energy Values
| Orbit | State | Energy |
|---|---|---|
| n = 1 | Ground state | -13.6 eV |
| n = 2 | First excited state | -3.40 eV |
| n = 3 | Second excited state | -1.51 eV |
| n = ∞ | Free electron | 0 eV |
CBSE: Class 12
Key Points: Energy Levels
- Ground state energy of hydrogen = -13.6 eV.
- Ionisation energy of hydrogen in the ground state = 13.6 eV.
- Energy required for first excitation = 10.2 eV.
- Energy required for second excitation = 12.09 eV.
- The energy of a free electron is 0 eV.
