Complete Physics Notes on Everyday Physics Applications for BPSC and Other Competitive Exams in 2025
General Science-6 (Physics)
Here’s an explanation of these everyday physics applications relevant to the BPSC CCE
Everyday Physics Applications
1. Batteries
- Basic Concept: A battery is a device that converts chemical energy into electrical energy through a series of electrochemical reactions (redox reactions) within its cells.
- Working Principle: It consists of one or more electrochemical cells. Each cell has two electrodes (an anode and a cathode) separated by an electrolyte. A chemical reaction occurs at the anode, releasing electrons, and another reaction occurs at the cathode, consuming electrons. This creates a potential difference (voltage) between the terminals, allowing current to flow when connected to a circuit.
- Types:
- Primary Batteries (Non-rechargeable): Designed for single use, as the chemical reactions are irreversible (e.g., dry cells like AA, AAA batteries, button cells).
- Secondary Batteries (Rechargeable): Can be recharged by applying an external electric current, which reverses the chemical reactions (e.g., lead-acid batteries in cars, lithium-ion batteries in mobile phones and laptops, Ni-Cad, Ni-MH).
- Key Terms:
- Electrolyte: A substance (often a solution) that conducts electricity through the movement of ions.
- Electrodes: Conductors through which current enters or leaves the electrolyte.
- Voltage: The potential difference provided by the battery.
- Capacity (Ah): The amount of charge a battery can deliver at its rated voltage.
- Applications: Powering portable electronic devices (phones, flashlights, remote controls), starting vehicles, backup power systems, electric vehicles.
2. Transformers
- Basic Concept: A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. It is used to increase or decrease AC voltage.
- Working Principle: It consists of two coils of wire (primary and secondary) wound around a common soft iron core. When an alternating current (AC) flows through the primary coil, it creates a continuously changing magnetic field in the core. This changing magnetic field induces an alternating electromotive force (EMF) and thus current in the secondary coil, according to Faraday’s Law of Electromagnetic Induction.
- Types:
- Step-up Transformer: Increases voltage (and decreases current). Has more turns in the secondary coil than in the primary coil. Used at power generation stations to increase voltage for long-distance transmission, minimizing power loss.
- Step-down Transformer: Decreases voltage (and increases current). Has fewer turns in the secondary coil than in the primary coil. Used near homes and industries to reduce high transmission voltages to usable levels.
- Importance: Transformers are crucial for the efficient transmission of electricity over long distances. High voltage transmission reduces current, thereby minimizing power loss (Ploss=I2R) in transmission lines.
- Note: Transformers work ONLY with Alternating Current (AC), not Direct Current (DC).
3. Electric Bulbs (Incandescent and LED)
a) Incandescent Bulbs
- Basic Concept: An older type of electric bulb that produces light by heating a metallic filament (usually tungsten) to a very high temperature until it glows.
- Working Principle: Electric current passes through a thin, high-resistance tungsten filament. Due to the heating effect of electric current (H=I2Rt), the filament gets extremely hot (up to 2700∘C) and emits light (incandescence) and heat. The bulb is usually filled with an inert gas (like argon or nitrogen) to prevent the filament from oxidizing and evaporating too quickly.
- Efficiency: Very inefficient, as most of the electrical energy is converted into heat (about 90%) rather than light (about 10%).
- Applications: General lighting (being phased out due to inefficiency).
b) LED Bulbs (Light Emitting Diodes)
- Basic Concept: A semiconductor device that emits light when an electric current passes through it.
- Working Principle: LEDs are p-n junction diodes. When a voltage is applied across the p-n junction in the forward bias, electrons and holes recombine, releasing energy in the form of photons (light).
- Efficiency: Highly energy-efficient, converting a much larger percentage of electrical energy into light and very little into heat. They have a much longer lifespan compared to incandescent bulbs.
- Applications: General lighting, indicator lights, displays (TVs, smartphones), traffic lights, automotive lighting.
4. Solar Cells (Photovoltaic Cells)
- Basic Concept: A device that converts light energy (photons) directly into electrical energy (electricity) through the photovoltaic effect.
- Working Principle: Most solar cells are made of semiconductor materials (like silicon). When sunlight (photons) strikes the cell, the energy from the photons knocks electrons loose from the atoms in the semiconductor material. These free electrons are then forced to move in a particular direction by the electric field within the cell, creating an electric current.
- Photovoltaic Effect: The generation of a voltage and electric current in a material upon exposure to light.
- Key Feature: Direct conversion of light into electricity without any moving parts.
- Applications: Solar panels for residential and commercial power generation, calculators, watches, satellites, remote power systems, solar-powered vehicles.
- Advantages: Renewable, clean energy source, low maintenance.
- Disadvantages: Intermittent (depends on sunlight), high initial cost (though decreasing), energy storage required for continuous power.
