NCERT Class 6th Science Chapter 9 Electricity and Circuits Notes

𝗤𝗨𝗜𝗭𝗘𝗧

NCERT Class 6th Science Chapter 9 Electricity and Circuits Notes

Introduction to Electricity

• Uses of Electricity: Electricity is an essential part of modern life, used for various purposes, including operating pumps to lift water, lighting homes, roads, and offices, and powering appliances. Electricity allows us to continue working even after sunset by providing light.
• Power Stations: Electricity is generated at power stations and distributed to homes and businesses. However, electricity supply may sometimes fail or be unavailable in certain areas.
• Torch as a Source of Light: In situations where electricity is unavailable, a torch can be used as a source of light. A torch contains a bulb that lights up when switched on. The electricity for the torch bulb comes from an electric cell (battery).

Electric Cell

• Function of an Electric Cell: An electric cell is a device that produces electricity from chemicals stored inside it. When the chemicals are exhausted, the cell stops producing electricity and needs to be replaced.
• Structure of an Electric Cell:
  • An electric cell has two terminals: a positive terminal (metal cap) and a negative terminal (metal disc).
  • The electric cell provides the energy needed to power various devices, such as alarm clocks, wristwatches, and radios.

Torch Bulb

• Structure of a Torch Bulb:
  • The bulb has a glass outer case fixed to a metallic base.
  • Inside the glass case, there is a thin wire called the filament.
  • The filament is supported by thicker wires connected to the base of the bulb.
  • The bulb has two terminals: the metal base and the metal tip of the base.
• Functioning of a Bulb:
  • When the bulb is connected to an electric cell through wires, the current passes through the filament, making it glow.
  • If the filament breaks (fuses), the circuit is incomplete, and the bulb does not light up.

Electric Circuit

• Definition of an Electric Circuit: An electric circuit is a complete path through which electricity flows. It consists of an electric cell, wires, and a bulb.
• Activity to Connect a Bulb to a Cell:
  • Using wires, connect the terminals of the electric cell to the terminals of the bulb.
  • The bulb will light up if the connections are made correctly, completing the circuit.
  • The current flows from the positive terminal of the cell to the negative terminal through the circuit.
• Reasons for Bulb Not Lighting:
  • Incorrect connections or a broken filament in the bulb can prevent the bulb from lighting up, as the circuit is incomplete.

Electric Switch

• Purpose of an Electric Switch:
  • A switch is a device that can either complete or break an electric circuit, controlling whether a device (like a bulb) is on or off.
• Making a Simple Switch:
  • A simple switch can be made using drawing pins, a safety pin, and a thermocol or wooden board.
  • By rotating the safety pin to connect or disconnect the drawing pins, the circuit can be completed or broken.
  • When the circuit is complete (switch is on), the bulb lights up; when the circuit is broken (switch is off), the bulb does not light up.

Electric Conductors and Insulators

• Conductors: Materials that allow electric current to pass through them are called conductors. Metals like copper and aluminum are common conductors and are used to make wires.
• Insulators: Materials that do not allow electric current to pass through them are called insulators. Examples include rubber, plastic, and wood.
• Activity to Test Conductors and Insulators:
  • Use a simple circuit with a bulb to test various materials by connecting them in the circuit and observing whether the bulb lights up.
  • If the bulb lights up, the material is a conductor; if it doesn’t, the material is an insulator.
• Importance of Insulators: Insulators are used to cover electrical wires and components to prevent accidental contact with electricity, ensuring safety.

Safety with Electricity

• Danger of Electricity: Electricity can be dangerous if not handled properly, leading to severe injuries or even death.
• Caution: Never attempt to experiment with electric wires and sockets. Always use electric cells for activities involving electricity. Remember, even electricity from portable generators is dangerous.
• Your Body as a Conductor: The human body conducts electricity, so it is crucial to be cautious when handling electrical appliances.

Activity: Making a Simple Circuit

• Objective: To understand how to connect a bulb to an electric cell using wires to complete a circuit.

• Materials Needed:

  • An electric cell
  • A torch bulb
  • Electric wires with plastic coverings (with the ends stripped to expose the metal)
  • Tape or rubber bands

• Procedure:

  1. Take four lengths of electric wire and strip off the plastic covering at the ends to expose the metal.
  2. Fix two wires to the terminals of the electric cell using tape or rubber bands.
  3. Fix the other two wires to the terminals of the bulb.
  4. Connect the wires from the bulb to the wires from the cell in various ways.
  5. Observe in which arrangements the bulb lights up.

• Observation:

  • The bulb lights up only when there is a complete path for the current to flow from the positive terminal of the cell to the negative terminal through the bulb.
  • The circuit must be complete without any gaps for the bulb to glow.

Electric Circuits and Symbols

• Introduction to Circuit Diagrams:

  • Circuit diagrams use symbols to represent components like electric cells, bulbs, and switches.
  • The positive and negative terminals of the cell are represented by short and long parallel lines, respectively.
  • Wires are represented by lines, and the bulb is shown as a circle with a cross inside it.
  • Switches are represented by breaks in the line that can be open (off) or closed (on).

• Example Circuit Diagram:

  • A simple circuit connecting a bulb to a cell with a switch can be represented using symbols. When the switch is closed, the circuit is complete, and the bulb lights up.

Electric Switches

• Function of a Switch:
  • A switch is used to control the flow of electricity in a circuit. It can turn the circuit on or off by closing or opening the gap in the circuit.
  • The design of the switch is essential to ensure it works correctly and is easy to use.
• Making an Improved Switch:
  • Use a safety pin and drawing pins to make a simple switch.
  • Fix the safety pin so that it can rotate and either touch another pin to close the circuit or move away to open the circuit.
  • This simple switch can be connected to the circuit, allowing you to control when the bulb lights up.

Conductors and Insulators

• Importance of Conductors:

  • Conductors are materials that allow electricity to flow through them easily. Metals are typically good conductors and are used to make wires and other electrical components.

• Importance of Insulators:

  • Insulators are materials that do not allow electricity to flow through them. They are used to cover and protect wires and other electrical components to prevent accidents.

• Testing Conductors and Insulators:

  • You can test whether a material is a conductor or insulator by connecting it in a circuit and seeing if the bulb lights up.
  • Common conductors include metals like copper, aluminum, and steel.
  • Common insulators include rubber, plastic, wood, and glass.

Safety Precautions with Electricity

• Handling Electrical Devices:

  • Always be cautious when handling electrical devices, as improper use can lead to accidents.
  • Never experiment with electric wires or sockets unless under supervision or using safe, low-voltage sources like electric cells.

• Electricity and the Human Body:

  • The human body is a conductor of electricity, so coming into direct contact with electrical sources can be dangerous.
  • Ensure that electrical devices are properly insulated and never touch live wires.

Summary of Key Concepts

• Electricity: A form of energy used to power various devices, allowing us to perform tasks easily.
• Electric Cell: A source of electricity used in small devices like torches, clocks, and radios.
• Electric Circuit: A complete path through which electricity flows, consisting of a power source (electric cell), conductors (wires), and a device (bulb).
• Switch: A device used to control the flow of electricity in a circuit, turning it on or off.
• Conductors and Insulators: Conductors allow electricity to flow through them, while insulators do not. Both are essential in designing and using electrical devices safely.