- Electric energy from a cell is used to do work on charges, which is converted into heat in a resistor or other forms, like motion in a motor.
- The work done (energy) in moving a charge Q across a potential difference VAB is:
Work = VAB × Q - Heat produced (H) in a resistor over time t is given by Joule’s Law of Heating:
H = I2 × R × t - According to Ohm’s Law:
VAB = I × R - Electrical power (P) is the rate of energy transfer and is calculated as:
P = VAB × I
Its unit is watt (W), where 1W = 1 volt × 1 ampere.
Definitions [10]
Definition: Geo Thermal Energy
The energy released in nuclear disintegrations in the interior of Earth gets stored deep inside the Earth and is called geo thermal energy.
Define.
Nuclear fission
In nuclear fission, the atom of a heavy element is bombarded by a neutron to form an unstable isotope which further splits into two or more smaller nuclei releasing extra neutrons and large amount of energy and heat.
Define the term potential difference.
The amount of work done in moving a unit positive charge from one point to another point in an electric field is called the potential difference.
Definition: Energy Bands
The different energy levels with continuous energy variation are called energy bands.
Definition: Valence Band
The range of energies possessed by valence electrons is called valence band.
Definition: Conduction Band
The range of energies possessed by conduction electrons is called conduction band.
Definition: Semiconductors
The material with electrical conductivity between that of a conductor and an insulator, whose number of charge carriers can be controlled as per requirement, is called a semiconductor. (e.g. Silicon, Germanium)
Definition: Conductors
The solids which have a large number of free electrons are called conductors. (e.g. Iron, Aluminium)
Definition: Insulators
The solids which have very small number of free electrons are called insulators. (e.g. Glass, Wood)
Definition: Forbidden Energy Gap
The energy difference between the valence band and the conduction band is called forbidden energy gap.
Theorems and Laws [1]
State Ohm’s law.
At constant temperature, the current flowing through a conductor is directly proportional to the potential difference across its ends.
In formula form: V = IR
Where:
- V = Voltage (potential difference)
- I = Current
- R = Resistance
Key Points
Key Points: Electricity Generation using Hydroelectric Energy
- Working Principle: Hydroelectric power plants use the potential energy of water stored in a reservoir, which converts into kinetic energy as water flows down.
- Turbine and Generator: The flowing water (kinetic energy) drives a water turbine, which in turn rotates a generator to produce electrical energy.
- Energy Conversion:
Potential energy of water → Kinetic energy of flowing water → Kinetic energy in turbine → Electrical energy - No Fuel Pollution: Since no fuel is burned in hydroelectric plants, there is no air pollution from combustion.
- Advantages & Concerns: Hydroelectric power gives uninterrupted generation if water is available, but reservoir storage may submerge land and affect living things in the river ecosystem.
Key Points: Power Plants Based on Nuclear Energy
- Working Principle: Nuclear fission of Uranium-235 or Plutonium releases heat, which is used to convert water into steam.
- Electricity Generation: The high-pressure steam rotates the turbine, which drives the generator to produce electricity.
- Energy Transformation: Nuclear energy → Thermal energy → Kinetic energy in steam → Kinetic energy in turbine → Electrical energy.
- Advantages: No air pollution, efficient source of energy, and less fuel required compared to thermal power plants.
- Problems: Produces radioactive nuclear waste and any accident can release harmful radiation.
Key Points: Electric Circuit
Key Points: Energy Bands in Solids
- Conductors → Eg = 0 - bands overlap, electrons flow freely.
- Semiconductors → Eg < 3 eV — small gap, conducts at room temperature.
- Insulators → Eg > 5 eV — large gap, no conduction.
- Ge = 0.72 eV, Si = 1.1 eV — both semiconductors.
- Metal conductivity decreases with temp. Semiconductor conductivity increases with temp.
Concepts [14]
- Electricity
- Sources of Electricity
- Forms of Energy > Geo Thermal Energy
- Electricity Generation using Hydroelectric Energy
- Power Plants Based on Nuclear Energy
- Electric cell
- Battery
- Electric Circuit
- Types of Circuits: Simple Circuit
- Types of Circuits: Series Circuit
- Types of Circuits: Parallel Circuit
- Symbols and Functions of Various Components of an Electric Circuits
- Electrical Conduction in Solids
- Precautions to Be Taken While Using Electricity
