Electricity: Circuits and their ComponentsClass 7 Science Notes
Electricity: Circuits and their Components
Nihal and his classmates learned about electricity and its uses, including cooking, lighting, transportation, heating/cooling, entertainment, communication and other applications like water pumps and computers. Electricity is generated in various ways, such as by windmills, solar panels, falling water, natural gas, or coal. It reaches our homes through wires, allowing us to power various devices.
A Torchlight
A torchlight, also called a torch or a flashlight, uses electricity to produce light. It contains a lamp, a switch, and electric cells. When the switch is slid to the "on" position, the lamp glows.
Inside a torchlight, you will find one or more electric cells.
A Simple Electrical Circuit
To understand how a torch works, it is important to know about its components.
Electric cell
An electric cell is a portable source of electrical energy. It has two terminals: a positive (+ve) terminal and a negative (-ve) terminal. The metal cap is the positive terminal, and the metal disc is the negative terminal.
Battery
A battery is a combination of two or more electric cells. In a torch, cells are placed in a specific order, with the positive terminal of one cell connected to the negative terminal of the next cell. Connecting more than one cell provides energy to the circuit for a longer time and/or more energy.
Electric lamp
Incandescent Lamp
An incandescent lamp (or light bulb) has a thin wire in the middle of a glass bulb called a filament. When the torch is switched on, the filament glows, producing light. The filament is attached to two thicker wires that connect to the terminals at the lamp's base. The filament gets hot and glows to produce light.
LED Lamp
Many torches use a Light Emitting Diode (LED) lamp instead of an incandescent lamp. Unlike incandescent lamps, LEDs do not have a filament. LEDs also have two terminals: a positive terminal (attached to a longer wire) and a negative terminal (the shorter wire).
Making an electric lamp glow using an electric cell or battery
To make an electric lamp glow, you need an electric cell, a lamp, a cell holder, a lamp holder, and electric wires. The wires are attached to the ends of the cell holder and the screws of the lamp holder. The cell is inserted into the holder with its negative terminal towards the spring side.
An electrical circuit
An electrical circuit is a complete path for electric current to flow through a lamp. The lamp glows when one terminal of the lamp is connected to one terminal of the electric cell, and the other terminal of the lamp is connected to the other terminal of the cell. The direction of electric current in an electrical circuit is taken to be from the positive to the negative terminal of the electric cell. When the terminals of the lamp are connected to those of the electric cell by wires, the current passes through the filament of the incandescent lamp and makes it glow.
To make an LED glow, connect the positive terminal (longer wire) of the LED to the positive terminal of the battery and the negative terminal (shorter wire) of the LED to the negative terminal of the battery. Current can pass through the LED in one direction only.
Electric switch
A switch is a device used to turn on or off a torchlight. It either completes or breaks the circuit.
To make a simple switch:
- Collect two drawing pins, a safety pin (or a paper clip), two wires, and a small piece of cardboard.
- Insert a drawing pin through the ring of the safety pin and fix it to the cardboard piece, ensuring that the safety pin can rotate freely.
- Fix the second drawing pin to the cardboard piece so the free end of the safety pin can touch it.
- Connect a wire to each drawing pin - the switch is ready!
When the safety pin touches both drawing pins, it closes the gap and completes the path, allowing the current to flow. This is the ON position, where the circuit is closed, and current flows from the cell's positive to negative terminal, making the lamp glow. When the safety pin does not touch the second drawing pin, the gap in the circuit prevents current flow, and the lamp does not glow. This is the OFF position, and the circuit is open.
Circuit Diagrams
A circuit diagram is a representation of an electrical circuit using symbols.
| Electrical Component | Symbol Electrical Conductors and Insulators Why are metal wires used for making electric circuits? Can't we use other materials? Also, why are electric wires covered with plastic or rubber?
Conductors are materials through which electric current can flow easily. Insulators are materials through which current cannot pass. Metals are conductors of electricity and are used for making wires. Silver, copper, and gold are the best electrical conductors. However, copper is mainly used for making electrical wires due to its lower cost and abundant supply. Plastic, rubber, and ceramics are electrical insulators and are used to cover wires.
There are two types of electricity: Direct Current (DC) and Alternating Current (AC). Electricity from batteries is usually DC and powers small devices. Electricity from power plants is AC and can run larger appliances.