Chapter: Electricity - Class 8 Science
Electricity
➥ Electricity is the flow of electric charge, typically through a conductor like a wire.
Charge
➥ Charge is a property of matter that causes it to experience a force when placed in an electric or magnetic field.
➥ There are two types of Charges:-
1) Positive Charge
2) Negative Charge
➥ Same charges repel each other and different charges attract each other.
➥ SI unit of charge is Coulomb (C).
➥ 1 Coulomb means 6.24 x 1018 electrons.
➥ An electron has a negative charge of 1.6 x 10-19 C.
Electric Current
➥ The rate of flow of charge is called Current.
➥ Movement of Electrons makes Current.
➥ In an electric circuit, the direction of electric current is taken as opposite to the direction of the flow of electrons.
i.e., if electrons are moving to the left, then the current is moving to the right.
➥ The unit of electric current is the ampere (A).
➥ It is denoted by the symbol 'I'.
➥ I = Q / t, where I = Current, Q = Charge, and t = Time.
➥ 1 Ampere current is defined as the flow of one coulomb of charge per second.
➥ Current is measured by an Ammeter, and it is always connected in series.
Conductors & Insulators
Conductors: Materials that allow electricity to flow easily, such as metals like copper and aluminum, which are used in wiring.
Insulators: Materials that do not allow electricity to pass through them, like plastic, rubber, and wood, which are used to cover wires to protect us from electric shocks.
➯ The wires in your home have a metal core (conductor) covered with plastic (insulator) to ensure safety.
Testing the Conductivity of Liquids
How It Works: A simple circuit with a bulb and liquid can be used to test if a liquid conducts electricity. If the bulb glows, the liquid is a good conductor.
Conductors: Liquids like saltwater and lemon juice allow electricity to pass through.
Insulators: Liquids like distilled water and oil do not conduct electricity.
Example: Saltwater makes the bulb glow because it is a conductor.
Electrolysis
Electrolysis: A process in which an electric current causes a chemical change in a liquid. The liquid used in this process is called an electrolyte.
Example: Breaking down water into hydrogen and oxygen using electricity.
Use: It is used to purify metals and produce chemicals.
Chemical Effects of Electric Current
➥ When an electric current passes through a liquid, it can cause chemical changes, such as:
- Color changes in the liquid.
- Bubbles forming in the liquid.
- Metal deposition on the electrodes (the parts dipped in the liquid).
Example: Electroplating is an example where a metal layer is deposited on an object using electricity.
Applications of Chemical Effects of Current
Electroplating: Coating one metal with another to make it shinier or rust-resistant.
Electrorefining: Using electricity to purify metals like copper.
Chemical Production: Electricity is used to produce chemicals such as chlorine.
Example: Many kitchen utensils are electroplated to appear shiny and resist rusting.
Uses of Electroplating
Rust Prevention: Electroplating helps protect metal objects from rust, for example, bicycle parts, taps, and car parts are often electroplated.
Making Things Shiny: Jewelry and watches are electroplated with gold or silver to make them more attractive.
Example: Gold-plated jewelry is more affordable and still looks shiny and attractive.
Safety Precautions for Electricity
➥ Electricity can be dangerous, so it is important to follow safety precautions such as:
- Never touch electrical appliances with wet hands.
- Always use properly insulated wires.
- Turn off electrical devices when not in use.
- Do not overload circuits with too many devices.
- Use a fuse or circuit breaker to prevent overloading.
- Call an electrician for repairs instead of trying to fix it yourself.
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